The Mesozoic volcanic rocks of the Bodong Low Uplift in the Bohai Bay Basin have been studied and explored for years.In 2024,the LK7-A well drilled in this region tested high-yield oil and gas flows from volcanic weat...The Mesozoic volcanic rocks of the Bodong Low Uplift in the Bohai Bay Basin have been studied and explored for years.In 2024,the LK7-A well drilled in this region tested high-yield oil and gas flows from volcanic weathered crust.These volcanic rocks need to be further investigated in terms of distribution patterns,conditions for forming high-quality reservoirs,and main factors controlling hydrocarbon accumulation.Based on the logging,geochemical and mineralogical data from wells newly drilled to the Mesozoic volcanic rocks in the basin,and high-resolution 3D seismic data,a comprehensive study was conducted for this area.The research findings are as follows.First,the volcanic rocks in the LK7-A structure are adakites with a large source area depth,and the deep and large faults have provided channels for the emplacement of intermediate-acidic volcanic rocks.Second,volcanic rock reservoirs are mainly distributed in tectonic breccias and intermediate-acidic lavas,and they are dominantly fractured-porous reservoirs,with high-porosity and low-permeability or medium-porosity and low-permeability.Third,the dominant lithologies/lithofacies is the basic condition for forming large-scale volcanic rock reservoirs.Structural fractures and late-stage strong weathering are crucial mechanisms for the formation scale of reservoirs in the Mesozoic volcanic rocks.Fourth,the Bodong Low Uplift exhibits strong hydrocarbon charging by two sags and overpressure mudstone capping,which are favorable for forming high-abundance oil and gas reservoirs.The Mesozoic volcanic buried hills in the study area reflect good trap geometry,providing favorable conditions for large-scale reservoir formation,and also excellent migration and accumulation conditions.Areas with long-term exposure of intermediate-acidic volcanic rocks,particularly in active structural regions,are the key targets for future exploration.展开更多
Guided by the fundamental principles of the whole petroleum system,the control of tectonism,sedimentation,and diagenesis on hydrocarbon accumulation in a rifted basin is studied using the data of petroleum geology and...Guided by the fundamental principles of the whole petroleum system,the control of tectonism,sedimentation,and diagenesis on hydrocarbon accumulation in a rifted basin is studied using the data of petroleum geology and exploration of the second member of the Paleogene Kongdian Formation(Kong-2 Member)in the Cangdong Sag,Bohai Bay Basin,China.It is clarified that the circle structure and circle effects are the marked features of a continental fault petroliferous basin,and they govern the orderly distribution of conventional and unconventional hydrocarbons in the whole petroleum systems of the rifted basin.Tectonic circle zones control sedimentary circle zones,while sedimentary circle zones and diagenetic circle zones control the spatial distribution of favorable reservoirs,thereby determining the orderly distribution of hydrocarbon accumulations in various circles.A model for the integrated,systematic accumulation of conventional and unconventional hydrocarbons under a multi-circle structure of the whole petroleum system of continental rifted basin has been developed.It reveals that each sag of the rifted basin is an independent whole petroleum system and circle system,which encompasses multiple orderly circles of conventional and unconventional hydrocarbons controlled by the same source kitchen.From the outer circle to the middle circle and then to the inner circle,there is an orderly transition from structural and stratigraphic reservoirs,to lithological and structural-lithological reservoirs,and finally to tight oil/gas and shale oil/gas enrichment zones.The significant feature of the whole petroleum system is the orderly control of hydrocarbons by multi-circle stratigraphic coupling,with the integrated,orderly distribution of conventional and unconventional reserves being the inevitable result of the multi-layered interaction within the whole petroleum system.This concept of multi-circle stratigraphic coupling for the orderly,integrated accumulation of conventional and unconventional hydrocarbons has guided significant breakthroughs in the overall,three-dimensional exploration and shale oil exploration in the Cangdong Sag.展开更多
Based on the achievements and research advances in oil and gas exploration in the Persian Gulf Basin,this study analyzes the orderliness of oil and gas distribution and main controlling factors of hydrocarbon accumula...Based on the achievements and research advances in oil and gas exploration in the Persian Gulf Basin,this study analyzes the orderliness of oil and gas distribution and main controlling factors of hydrocarbon accumulation with reservoir-forming assemblage as the unit.In the Persian Gulf Basin,the hydrocarbon-generating centers of source rocks of different geological ages and the hydrocarbon rich zones migrate in a clockwise direction around the Ghawar Oilfield in the Central Arabian Subbasin.Horizontally,the overall distribution pattern is orderly,showing“oil in the west and gas in the east”,and“large oil and gas fields dense in the basin center and sparse at the basin edges”.Vertically,the extents of petroleum system compounding and sources mixing increase from west to east,the pattern of tectonic strength(weak in the west and strong in the east)forming the distribution characteristics of“gas rich in the Paleozoic,oil rich in the Mesozoic,and both oil and gas rich in the Cenozoic”.The large scale accumulation and orderly distribution of oil and gas in the Persian Gulf Basin are controlled by three factors:(1)Multiple sets of giant hydrocarbon kitchens provide a resource base for near-source reservoir-forming assemblages.The short-distance lateral migration determines the oil and gas enrichment in and around the distribution area of effective source rocks.(2)The anhydrite caprocks in the platform area are thin but have experienced weak late-stage tectonic activities.Their good sealing performance makes it difficult for oil and gas to migrate vertically to shallow layers through them.The thrust faults and high-angle fractures formed by intense tectonic activities of the Zagros Orogenic Belt connect multiple source-reservoir assemblages.However,the Neogene Gachsaran Formation gypsum-salt rocks are thick and highly plastic,generally with good sealing performance,so large-scale oil and gas accumulations are still formed beneath the salt;(3)Each set of reservoir-forming assemblages is well matched in time and space in terms of the development of source rocks and reservoir-caprock assemblages,the maturation and hydrocarbon generation of source rocks,and the formation of traps,thus resulting in abundant multi layer hydrocarbon accumulations.At present,the Persian Gulf Basin is still in the stage of structural trap exploration.The pre-salt prospective traps in effective hydrocarbon kitchens remain the first choice.The areas with significant changes in Mesozoic sedimentary facies have the conditions to form large scale lithologic oil and gas reservoirs.The deep Paleozoic conventional oil and gas reservoirs and the Lower Silurian Qusaiba Member shale gas have great exploration potential and are expected to become important reserve growth areas in the future.展开更多
Focusing on the geochronological issues related to the matching relationship between the strike-slip fault activity and the stages of hydrocarbon generation,reservoir formation,and hydrocarbon accumulation,this study ...Focusing on the geochronological issues related to the matching relationship between the strike-slip fault activity and the stages of hydrocarbon generation,reservoir formation,and hydrocarbon accumulation,this study aims to quantitatively constrain the tectonic-burial history,hydrocarbon generation history,reservoir porosity evolution history,and hydrocarbon accumulation history by determining the isotopic ages and temperatures of multiphase calcites(particularly the calcites which contain hydrocarbon-bearing fluid inclusions)and quartzs filling the fractures in the Ordovician strata within the non-foreland area of Tarim Basin.Three major findings have been obtained.(1)According to the tectonic-burial history restored under the constraint of the isotopic ages and temperatures,the non-foreland area of the Tarim Basin experienced a continuous burial process during the Cambrian-Ordovician period,with only a minor uplift at the end of the Silurian.Overall,the area was characterized by continuous hydrocarbon generation and a gradual increase in vitrinite reflectance(Ro).(2)While mechanical compaction and pressure-solution during burial progressively reduced the matrix porosity,the strike-slip fault activity during the Middle Caledonian Ⅱ and Ⅲ episodes induced physical fragmentation,which created extensive interbreccia pores,fault cavities,and structural fractures as seepage pathways for surface runoff,and,in conjunction with interlayer karstification,led to the development of widespread dissolution vugs.The formation of fracture-vug system in the Ordovician limestone provided effective storage space for hydrocarbons generated during the Late Caledonian and subsequent periods.(3)The Ordovician fault-karst limestone reservoirs underwent four stages of hydrocarbon accumulation:low-medium maturity liquid hydrocarbons during the Middle-Late Caledonian,medium-high maturity liquid hydrocarbons during the Middle-Late Hercynian,high maturity liquid hydrocarbons during the Indosinian,and high-over maturity gas during the Middle Yanshanian.Variations in hydrocarbon accumulation among different strike-slip faults or different segments of the same fault are controlled by differences in source rock maturity across structural units,as well as by the timing of fault activity and fault-related connectivity to hydrocarbon sources.This research also establishes a geochronological framework for investigating strike-slip faultcontrolled reservoir formation and hydrocarbon accumulation,facilitating a more accurate determination of the reservoir formation and hydrocarbon accumulation stages,and providing critical insights for evaluating hydrocarbon enrichment zones in fault-controlled reservoirs.展开更多
Based on the investigation of sedimentary filling characteristics and pool-forming factors of the Mesozoic in the Ordos Basin,the whole petroleum system in the Mesozoic is divided,the migration&accumulation charac...Based on the investigation of sedimentary filling characteristics and pool-forming factors of the Mesozoic in the Ordos Basin,the whole petroleum system in the Mesozoic is divided,the migration&accumulation characteristics and main controlling factors of conventional-unconventional hydrocarbons are analyzed,and the whole petroleum system model is established.First,the whole petroleum system developed in the Mesozoic takes the high-quality source rocks of the 7th member of the Triassic Yanchang Formation as the core and mainly consists of low-permeability and unconventional oil and gas reservoirs.It can be divided into four hydrocarbon accumulation domains,including intra-source retained hydrocarbon accumulation domain,near-source tight hydrocarbon accumulation domain,far-source conventional hydrocarbon accumulation domain and transitional hydrocarbon accumulation domain,which together form a continuous,symbiotic,and orderly accumulation entity wherein unconventional resources significantly outweigh conventional ones in proportion.Second,the spatial core area of sedimentary filling is the oil-rich core of the whole petroleum system.From the core to the periphery,the reservoir type evolves as shale oil→tight oil→conventional oil,the accumulation power is dominated by overpressure→buoyancy or overpressure and capillary force,the accumulation scale changes from extensive hundreds of millions of tons to a isolated hundreds of thousands-million of tons,and the gas-oil ratio and methane content decrease.Third,the sedimentary filling system provides the material basis and spatial framework for the whole petroleum system,the superimposed sand body,fault and unconformity constitute the dominant migration pathway of hydrocarbons in the far-source conventional hydrocarbon accumulation domain and the transitional hydrocarbon accumulation domain,the high-quality source rocks provide a solid resource basis for shale oil,and the micro-nano pore throat-fracture network constitute unconventional accumulation space.The hydrocarbon migration and accumulation process is mainly controlled by intense expulsion of hydrocarbon under overpressure in the pool-forming stage and the in-situ re-enrichment controlled by underpressure in post-pool-forming stage.The oil-gas enrichment and long-term preservation depends on the coordination among three factors(stable geological structure,multi-cycle sedimentation,and dual self-sealing).Fourth,the whole petroleum system model is defined as four domains,overpressure+underpressure drive,and dual self-sealing.展开更多
There are abundant hydrothermal events within the Dengying Formation dolomite of the Precambrian system in southwest China.Methods including petrography identification,fluid-inclusion observation,in-situ U-Pb dating,a...There are abundant hydrothermal events within the Dengying Formation dolomite of the Precambrian system in southwest China.Methods including petrography identification,fluid-inclusion observation,in-situ U-Pb dating,and in-situ measurement of rare earth element(REE),etc.are integrated to characterize hydrothermal activity process within the Dengying Formation dolomite.The hydrothermal activity therein can be divided into four stages on the basis of in-situ U-Pb dating results of saddle dolomite cements.The 1st-stage(415.0-400.0 Ma)and 2nd-stage(259.4-248.0 Ma)hydrothermal events are characterized by saddle dolomite filling along the margin of fractures,or filling within dilational breccia and zebra textures.Compared with matrix dolomite and seawater-derived fibrous dolomite,saddle dolomite exhibits obvious negative anomalies of Ce elements.The 3rd-stage(225.6-199.0 Ma)hydrothermal event is represented by galena,sphalerite and other Mississipppi Valley-type(MVT)mineral cements in residual space.The formation of lead-zinc ore is due to the precipitation of metal sulfide caused by the thermo-chemical sulfate reduction(TSR)reaction between hydrothermal fluids and hydrocarbons during the large-scale hydrocarbon charging period.The 4th-stage(130.0-41.0 Ma)hydrothermal event is characterized by quartz and a small amount of fluorite filling the residual pores with dolomites.Quartz and fluorite record the migration of deep high-temperature hydrothermal fluid along early fractures and residual pores.During this period,the hydrothermal fluids result in the heterogeneous structure of bitumen,which is a clear response to high-temperature hydrothermal activity.展开更多
Based on two-dimensional/three-dimensional seismic and logging data,combined with the analysis of low-temperature thermochronology data,the unconformity surface characteristics and the patterns and dynamic mechanisms ...Based on two-dimensional/three-dimensional seismic and logging data,combined with the analysis of low-temperature thermochronology data,the unconformity surface characteristics and the patterns and dynamic mechanisms of inverted structures in the Doseo Basin in the Central and West African rift systems are systematically analyzed.Seismic profiles reveal two key inversion unconformable surfaces in the basin,i.e.the T_(5)interface within the Upper Cretaceous and the T_(4)interface at the top of the Cretaceous,which control the development of inverted structures in the basin.Four types of inverted structures,i.e.fault-associated,thrust,fold,and back-shaped negative flower,are identified.Spatially,they form six inverted structural belts trending in NE-NEE direction.The thermal history simulation of apatite fission track reveals two rapid cooling events in the late Late Cretaceous(85-80 Ma,cooling by 15℃)and the Eocene-Oligocene(30-40 Ma,cooling by 35℃),corresponding respectively to the formation periods of the T_(5)and T_(4)interface.The dynamics analysis of structural inversion indicates that the structural inversion in the Late Cretaceous was controlled by the subduction and long-range compression within the Tethys Ocean in the north of African Plate,while the structural inversion in the Eocene-Oligocene was drived by the stress transmission from the African-Eurasian collision.The two events were all controlled by the continuous tectonic regulation of the intracratonic basin by the evolution of the Tethys tectonic domain.The two periods of structural inversion enhanced the efficiency of oil and gas migration by controlling the types of traps(anticline and fault-related traps)and fault activation,precisely matching the hydrocarbon generation peaks of the Lower Cretaceous source rocks in the Late Cretaceous and Eocene,thereby controlling the formation of large-scale oil and gas reservoirs in the Doseo Basin.This geological insight provides a critical basis for the theoretical research on the evolution and hydrocarbon accumulation of inverted structures in discrete strike-slip rift systems.展开更多
With the development of unconventional hydrocarbon, how to improve the shale oil and gas recovery become urgent. Therefore hydraulic fracturing becomes the key due to the complicated properties of the reservoirs. The ...With the development of unconventional hydrocarbon, how to improve the shale oil and gas recovery become urgent. Therefore hydraulic fracturing becomes the key due to the complicated properties of the reservoirs. The pore structure not only plays an essential role in the formation of complex fracture networks after fracturing but also in resource accumulation mechanism analyses. The lacustrine organicrich shale samples were selected to carry out petrophysical experiments. Scanning Electron Microscopy(SEM) and X-ray Diffraction were performed to elucidate the geology characteristics. MICP, 2D NMR, CT,and N2adsorption were conducted to classify the pore structure types. The contribution of pore structure to oil accumulation and hydrocarbon enrichment was explained through the N2adsorption test on the original and extracted state and 2D NMR. The results show that micropores with diameter less than20 nm are well-developed. The pore structure was divided into three types. Type Ⅰ is characterized by high porosity, lower surface area, and good pore throat connectivity, with free oil existing in large pores,especially lamellation fractures. The dominant nano-pores are spongy organic pores and resources hosted in large pores have been expelled during high thermal evolution. The content of nano-pores(micropores) increases and the pore volume decreases in Type Ⅱ pore structure. In addition, more absorbed oil was enriched. The pore size distribution of type Ⅱ is similar to that of type Ⅰ. However, the maturity and hydrocarbon accumulation is quite different. The oil reserved in large pores was not expelled attributed to the relatively low thermal evolution compared with type Ⅰ. Structural vitrinite was observed through SEM indicating kerogen of type Ⅲ developed in this kind of reservoir while the type of kerogen in pore structure Ⅰ is type Ⅱ. Type Ⅲ pore structure is characterized by the largest surface area,lowest porosity, and almost isolated pores with rarely free oil. Type Ⅰ makes the most contribution to hydrocarbon accumulation and immigration, which shows the best prospect. Of all of these experiments,N2adsorption exhibits the best in characterizing pores in shales due to its high resolution for the assessment of nano-scale pores. MICP and NMR have a better advantage in characterizing pore space of sandstone reservoirs, even tight sandstone reservoirs. 2D NMR plays an essential role in fluid recognition and saturation calculation. CT scanning provides a 3D visualization of reservoir space and directly shows the relationship between pores and throats and the characteristics of fractures. This study hopes to guide experiment selection in pore structure characterization in different reservoirs. This research provides insight into hydrocarbon accumulation of shales and guidance in the exploration and development of unconventional resources, for example for geothermal and CCUS reservoirs.展开更多
The Pinghu slope belt in the Xihu sag of the East China Sea Shelf Basin(ECSSB) is a crucial hydrocarbon production area in eastern China. However, due to the complex geological conditions, publications have lacked com...The Pinghu slope belt in the Xihu sag of the East China Sea Shelf Basin(ECSSB) is a crucial hydrocarbon production area in eastern China. However, due to the complex geological conditions, publications have lacked comprehensive research on the spatial-temporal coupling relationships of primary factors that impact hydrocarbon accumulation in the Pinghu slope belt. Furthermore, the hydrocarbon distribution patterns and the controlling factors across different study areas within the same slope belt are not yet fully understood. This study extensively utilized three-dimensional seismic data, well logging data,geochemical analysis, fluorescence analysis, and oil testing and production data to address these issues.Following a “stratification and differentiation” approach, the study identified seven distinct hydrocarbon migration and accumulation units(HMAU) in the Pinghu slope area based on the structural morphology characteristics, hydrocarbon source-reservoir-cap rock patterns, hydrocarbon migration pathways, and hydrocarbon supply range. Detailed analysis was conducted to examine the hydrocarbon distribution patterns and controlling factors within each migration and accumulation unit across different structural units, including high, medium, and low structural components. All data sources support a “southern-northern sub-area division, eastern-western sub-belt division, and variations in hydrocarbon accumulation” pattern in the Pinghu slope belt. The degree of hydrocarbon accumulation is controlled by the factors of structural morphology, hydrocarbon generation potential of source rocks, the spatial position of source slopes, fault sealing capacity, and sand body distribution. Furthermore, different coupling patterns of faults and sand bodies play a pivotal role in governing hydrocarbon enrichment systems across various migration and accumulation units. These observations indicate that three hydrocarbon accumulation patterns have been established within the slope belt, including near-source to far-source gentle slope with multiple hydrocarbon kitchens in the XP1-XP4 zones, near-source to middle-source gentle slope with dual-hydrocarbon kitchens in the XP5 zone, and near-source steep slope with a single hydrocarbon kitchen in the XP6-XP7 zones. These findings contribute to enhancing the theoretical system of hydrocarbon accumulation in the slope belt.展开更多
The hydrocarbon accumulation coefficient is a key parameter in resources evaluation by genetic techniques. Methods of obtaining its value scientifically have always been an important factor influencing evaluation cred...The hydrocarbon accumulation coefficient is a key parameter in resources evaluation by genetic techniques. Methods of obtaining its value scientifically have always been an important factor influencing evaluation credibility. In this paper, the hydrocarbon accumulation system is evaluated quantitatively by establishing a hierarchy structure model based on an analytical hierarchy process. The hydrocarbon accumulation system of a higher exploration degree is selected as a calibration area and its hydrocarbon accumulation coefficient can be calculated using methods of hydrocarbon generation potential and reservoir-scale sequence. The hydrocarbon accumulation coefficient of a petroleum accumulation system can be gained by analogy of reservoir forming comprehensive evaluation results with the calibration area. The hydrocarbon accumulation coefficient of each petroleum accumulation system in the upper reservoir-forming combination of the Liaohe Western Sag can be obtained with this method. Practice shows that using the analytical hierarchy process to quantitatively evaluate the hydrocarbon accumulation system and then quantitatively predict the hydrocarbon accumulation coefficient decreases the influence of human factors in resources evaluation, and makes the resources assessment more objective and closer to the actual geological condition.展开更多
According to the latest drilling and the analysis of the burial history,source rock evolution history and hydrocarbon accumulation history,the sub-source hydrocarbon accumulation characteristics of the Permian reservo...According to the latest drilling and the analysis of the burial history,source rock evolution history and hydrocarbon accumulation history,the sub-source hydrocarbon accumulation characteristics of the Permian reservoirs in the Jinan Sag,eastern Junggar Basin,are clarified,and the hydrocarbon accumulation model of these reservoirs is established.The results are obtained in four aspects.First,the main body of the thick salified lake basin source rocks in the Lucaogou Formation has reached the mature stage with abundant resource base.Large-scale reservoirs are developed in the Jingjingzigou,Wutonggou and Lucaogou formations.Vertically,there are multiple sets of good regional seals,the source-reservoir-caprock assemblage is good,and there are three reservoir-forming assemblages:sub-source,intra-source and above-source.Second,dissolution,hydrocarbon charging and pore-preserving effect,and presence of chlorite film effectively increase the sub-source pore space.Oil charging is earlier than the time when the reservoir becomes densified,which improves the efficiency of hydrocarbon accumulation.Third,buoyancy and source-reservoir pressure difference together constitute the driving force of oil charging,and the micro-faults within the formation give the advantage of"source-reservoir lateral docking"under the source rock.Microfractures can be critical channels for efficient seepage and continuous charging of oil in different periods.Fourth,the Jingjingzigou Formation experienced three periods of oil accumulation in the Middle-Late Permian,Middle-Late Jurassic and Late Neogene,with the characteristics of long-distance migration and accumulation in early stage,mixed charging and accumulation in middle stage and short-distance migration and high-position accumulation in late stage.The discovery and theoretical understanding of the Permian reservoirs in the Jinan Sag reveal that the thrust belt has good conditions for forming large reservoirs,and it is promising for exploration.The study results are of guidance and reference significance for oil and gas exploration in the Jinan Sag and other geologically similar areas.展开更多
As petroleum exploration advances and as most of the oil-gas reservoirs in shallow layers have been explored, petroleum exploration starts to move toward deep basins, which has become an inevitable choice. In this pap...As petroleum exploration advances and as most of the oil-gas reservoirs in shallow layers have been explored, petroleum exploration starts to move toward deep basins, which has become an inevitable choice. In this paper, the petroleum geology features and research progress on oil-gas reservoirs in deep petroliferous basins across the world are characterized by using the latest results of worldwide deep petroleum exploration. Research has demonstrated that the deep petroleum shows ten major geological features. （1） While oil-gas reservoirs have been discovered in many different types of deep petroliferous basins, most have been discovered in low heat flux deep basins. （2） Many types of petroliferous traps are developed in deep basins, and tight oil-gas reservoirs in deep basin traps are arousing increasing attention. （3） Deep petroleum normally has more natural gas than liquid oil, and the natural gas ratio increases with the burial depth. （4） The residual organic matter in deep source rocks reduces but the hydrocarbon expulsion rate and efficiency increase with the burial depth. （5） There are many types of rocks in deep hydrocarbon reservoirs, and most are clastic rocks and carbonates. （6） The age of deep hydrocarbon reservoirs is widely different, but those recently discovered are pre- dominantly Paleogene and Upper Paleozoic. （7） The porosity and permeability of deep hydrocarbon reservoirs differ widely, but they vary in a regular way with lithology and burial depth. （8） The temperatures of deep oil-gas reservoirs are widely different, but they typically vary with the burial depth and basin geothermal gradient. （9） The pressures of deep oil-gas reservoirs differ significantly, but they typically vary with burial depth, genesis, and evolu- tion period. （10） Deep oil-gas reservoirs may exist with or without a cap, and those without a cap are typically of unconventional genesis. Over the past decade, six major steps have been made in the understanding of deep hydrocarbon reservoir formation. （1） Deep petroleum in petroliferous basins has multiple sources and many dif- ferent genetic mechanisms. （2） There are high-porosity, high-permeability reservoirs in deep basins, the formation of which is associated with tectonic events and subsurface fluid movement. （3） Capillary pressure differences inside and outside the target reservoir are the principal driving force of hydrocarbon enrichment in deep basins. （4） There are three dynamic boundaries for deep oil-gas reservoirs; a buoyancy-controlled threshold, hydrocarbon accumulation limits, and the upper limit of hydrocarbon generation. （5） The formation and distribution of deep hydrocarbon res- ervoirs are controlled by free, limited, and bound fluid dynamic fields. And （6） tight conventional, tight deep, tight superimposed, and related reconstructed hydrocarbon reservoirs formed in deep-limited fluid dynamic fields have great resource potential and vast scope for exploration. Compared with middle-shallow strata, the petroleum geology and accumulation in deep basins are more complex, which overlap the feature of basin evolution in different stages. We recommend that further study should pay more attention to four aspects： （1） identification of deep petroleum sources and evaluation of their relative contributions; （2） preservation conditions and genetic mechanisms of deep high-quality reservoirs with high permeability and high porosity; （3） facies feature and transformation of deep petroleum and their potential distribution; and （4） economic feasibility evaluation of deep tight petroleum exploration and development.展开更多
The discovery of unconventional hydrocarbon resources since the late 20th century changed geologists’understanding of hydrocarbon migration and accumulations and provides a solution to energy shortage.In 2016,unconve...The discovery of unconventional hydrocarbon resources since the late 20th century changed geologists’understanding of hydrocarbon migration and accumulations and provides a solution to energy shortage.In 2016,unconventional oil production in the USA accounted for 41%of the total oil production;and unconventional natural gas production in China accounted for 35%of total gas production,showing strong growth momentum of unconventional hydrocarbons explorations.Unconventional hydrocarbons generally coexist with conventional petroleum resources;they sometimes distribute in a separate system,not coexisting with a conventional system.Identification and prediction of unconventional resources and their potentials are prominent challenges for geologists.This study analyzed the results of 12,237 drilling wells in six representative petroliferous basins in China and studied the correlations and differences between conventional and unconventional hydrocarbons by comparing their geological features.Migration and accumulation of conventional hydrocarbon are caused dominantly by buoyance.Wepropose a concept of buoyance-driven hydrocarbon accumulation depth to describe the deepest hydrocarbon accumulation depth driven dominantly by buoyance;beyond this depth the buoyance becomes unimportant for hydrocarbon accumulation.We found that the buoyance-driven hydrocarbon accumulation depth in petroliferous basins controls the different oil/gas reservoirs distribution and resource potentials.Hydrocarbon migration and accumulations above this depth is dominated by buoyancy,forming conventional reservoirs in traps with high porosity and permeability,while hydrocarbon migration and accumulation below this depth is dominated by non-buoyancy forces(mainly refers to capillary force,hydrocarbon volumeexpansion force,etc.),forming unconventional reservoirs in tight layers.The buoyance-driven hydrocarbon accumulation depths in six basins in China range from 1200mto 4200 m,which become shallowerwith increasing geothermal gradient,decreasing particle size of sandstone reservoir layers,or an uplift in the whole petroliferous basin.The predicted unconventional resource potential belowthe buoyance-driven hydrocarbon accumulation depth in six basins in China is more than 15.71×10^(9) t oil equivalent,among them 4.71×10^(9) t reserves have been proved.Worldwide,94%of 52,926 oil and gas reservoirs in 1186 basins are conventional reservoirs and only 6%of them are unconventional reservoirs.These 94%conventional reservoirs show promising exploration prospects in the deep area below buoyance-driven hydrocarbon accumulation depth.展开更多
Sichuan Basin is one of the uppermost petroliferous basins in China. It experienced three evolutionary phases which were marine carbonate platform （Ediacaran to Late Triassic）, Indosinian-Yanshanian orogeny foreland...Sichuan Basin is one of the uppermost petroliferous basins in China. It experienced three evolutionary phases which were marine carbonate platform （Ediacaran to Late Triassic）, Indosinian-Yanshanian orogeny foreland basin （Late Triassic to Late Cretaceous） and uplift and tectonic modification （Late Cretaceous to Quaternary）. The present-day tectonics of the Sichuan Ba- sin and its periphery are characterized by three basic elements which are topography, basement type and surface structure, and two settings （plate margin and interior）. Therefore, be subdivided into five units which have different structure and tectonic history. The basin contains five different sets of source rocks with thickness up to 2 500 m. These source rocks were well preserved due to the presence of Middel-Lower Triassic evaporites （〉-200 m） and thick terrestrial sediments filling in the Indosinian-Yanshanian foreland basin （〉3 000 m）. The uplift and erosion since Late Cretaceous has significant influence on cross-strata migration and accumulation of oil and gas. The multi-phase evolution of the basin and its superimposed tectonic elements, good petroleum geologic conditions and diverse petroleum systems reveal its bright exploration prospects.展开更多
The tectonic event during Cretaceous and its relationship with hydrocarbon accumulation in the Qiangtang Basin is discussed based on zircon U-Pb dating and the study of deformation, thermochronology and hydrocarbon fo...The tectonic event during Cretaceous and its relationship with hydrocarbon accumulation in the Qiangtang Basin is discussed based on zircon U-Pb dating and the study of deformation, thermochronology and hydrocarbon formation. LA-ICPMS zircon U-Pb dating indicates that the tectonic event took place during the Early-Late Cretaceous （125-75Ma）. The event not only established the framework and the styles of structural traps in the basin, but also led to the cessation of the first hydrocarbon formation and the destruction of previous oil pools. The light crude oil in the basin was formed during the second hydrocarbon formation stage in the Cenozoic, and ancient structural traps formed during the Cretaceous event are promising targets for oil and gas exploration.展开更多
Based on comprehensive analysis of reservoir-forming conditions, the diversity of reservoir and the difference of multistage hydrocarbon charge are the key factors for the carbonate hydrocarbon accumulation of the Ord...Based on comprehensive analysis of reservoir-forming conditions, the diversity of reservoir and the difference of multistage hydrocarbon charge are the key factors for the carbonate hydrocarbon accumulation of the Ordovician in the Tarim Basin. Undergone four major deposition-tectonic cycles, the Ordovician carbonate formed a stable structural framework with huge uplifts, in which are developed reservoirs of the reef-bank type and unconformity type, and resulted in multistage hydrocarbon charge and accumulation during the Caledonian, Late Hercynian and Late Himalayan. With low matrix porosity and permeability of the Ordovician carbonate, the secondary solution pores and caverns serve as the main reservoir space. The polyphase tectonic movements formed unconformity reservoirs widely distributed around the paleo-uplifts; and the reef-bank reservoir is controlled by two kinds of sedimentary facies belts, namely the steep slope and gentle slope. The unconventional carbonate pool is characterized by extensive distribution, no obvious edge water or bottom water, complicated oil/gas/water relations and severe heterogeneity controlled by reservoirs. The low porosity and low permeability reservoir together with multi-period hydrocarbon accumulation resulted in the difference and complex of the distribution and production of oil/gas/water. The distribution of hydrocarbon is controlled by the temporal-spatial relation between revolution of source rocks and paleo-uplifts. The heterogenetic carbonate reservoir and late-stage gas charge are the main factors making the oil/ gas phase complicated. The slope areas of the paleo-uplifts formed in the Paleozoic are the main carbonate exploration directions based on comprehensive evaluation. The Ordovician of the northern slope of the Tazhong uplift, Lunnan and its periphery areas are practical exploration fields. The Yengimahalla-Hanikatam and Markit slopes are the important replacement targets for carbonate exploration. Gucheng, Tadong, the deep layers of Cambrian dolomite in the Lunnan and Tazhong-Bachu areas are favorable directions for research and risk exploration.展开更多
The Tarim Basin is the largest petroliferous basin in the northwest of China, and is composed of a Paleozoic marine craton basin and a Meso-Cenozoic continental foreland basin. It is of great significance in explorati...The Tarim Basin is the largest petroliferous basin in the northwest of China, and is composed of a Paleozoic marine craton basin and a Meso-Cenozoic continental foreland basin. It is of great significance in exploration of Ordovician. In over 50 years of exploration, oil and gas totaling over 1.6 billion tonnes oil-equivalent has been discovered in the Ordovician carbonate formation. The accumulation mechanisms and distribution rules are quite complicated because of the burial depth more than 3,500 m, multi-source, and multi-stage accumulation, adjustment, reconstruction and re-enrichment in Ordovician. In this paper, we summarized four major advances in the hydrocarbon accumulation mechanisms of Ordovician carbonate reservoirs. First, oil came from Cambrian and Ordovician source rocks separately and as a mixture, while natural gas was mainly cracked gas generated from the Cambrian-Lower Ordovician crude oil. Second, most hydrocarbon migrated along unconformities and faults, with different directions in different regions. Third, hydrocarbon migration and accumulation had four periods： Caledonian, early Hercynian, late Hercynian and Himalayan, and the latter two were the most important for oil and gas exploration. Fourth, hydrocarbon accumulation and evolution can be generally divided into four stages： Caledonian （the period of hydrocarbon accumulation）, early Hercynian （the period of destruction）, late Hercynian （the period of hydrocarbon reconstruction and re-accumulation）, and Himalayan （the period of hydrocarbon adjustment and re-accumulation）. Source rocks （S）, combinations of reservoir-seal （C）, paleo-uplifts （M）, structure balance belt （B） matched in the same time （T） control the hydrocarbon accumulation and distribution in the Ordovician formations. Reservoir adjustment and reconstruction can be classified into two modes of physical adjustment and variation of chemical compositions and five mechanisms. These mechanisms are occurrence displacement, biodegradation, multi-source mixing, high-temperature cracking and late gas invasion. Late hydrocarbon accumulation effects controlled the distribution of current hydrocarbon. The T-BCMS model is a basic geological model to help understanding the control of reservoirs. At present, the main problems of hydrocarbon accumulation focus on two aspects, dynamic mechanisms of hydrocarbon accumulation and the quantitative models of oil-bearing in traps, which need further systemic research.展开更多
Sichuan Basin is a typical superimposed basin, which experienced multi-phase tectonic movements, meanwhile Sinian–Cambrian underwent complex hydrocarbon accumulation processes, causing exploration difficulties in the...Sichuan Basin is a typical superimposed basin, which experienced multi-phase tectonic movements, meanwhile Sinian–Cambrian underwent complex hydrocarbon accumulation processes, causing exploration difficulties in the past 60 years. Based on the microscopic evidence of fluid inclusions, combined with basin-modelling, this paper determines stages and time of hydrocarbon accumulation, reconstructs evolution of formation pressure and dynamic processes of hydrocarbon accumulation in Sinian Dengying Formation-Cambrian Longwangmiao Formation of Gaoshiti-Moxi structure. Three stages of inclusions are detected, including a stage of yellow-yellowgreen fluorescent oil inclusions, a stage of blue fluorescent oil-gas inclusions and a stage of non-fluorescent gas inclusions, reflecting the study area has experienced a series of complex hydrocarbon accumulation processes, such as formation of paleo-oil reservoirs, cracking of crude oil, formation of paleo-gas reservoirs and adjustment to present gas reservoirs, which occurred during 219–188, 192–146 and 168–0 Ma respectively. During the period of crude oil cracking, Dengying Formation-Longwangmiao Formation showed weak overpressure to overpressure characteristics, then after adjustment of paleo-gas reservoirs to present gas reservoirs, the pressure in Dengying Formation changed into overpressure but finally reduced to normal pressure system. However, due to excellent preservation conditions, the overpressure strength in Longwangmiao Formation only slightly decreased and was still kept to this day.展开更多
Similar reservoir sandbodies and fault conduit systems in the sandstone reservoirs in the middle Es3 member of the Niuzhuang Sag have been problematic for a long time. The following problems remain unsolved： 1） The ...Similar reservoir sandbodies and fault conduit systems in the sandstone reservoirs in the middle Es3 member of the Niuzhuang Sag have been problematic for a long time. The following problems remain unsolved： 1） The distribution of sandstone porosity is inconsistent with the hydrocarbon accumulation. The oil sandstones have low porosity instead of high porosity. 2） Sandstones, which have the same properties, have different levels of oiliness, and the sandstones with almost the same properties show different degrees of oil-bearing capacity. This study analyzes the condition of reservoirs in the research area during the accumulation period in terms of paleoporosity estimation and discusses the critical porosity of the sandstone reservoirs during the same period. The following conclusions can be drawn from the results. 1） Although reservoir properties are low at present and some reservoirs have become tight, the paleoporosity ranging from 18% to 25% is greater than the critical porosity of 13.9%. As the： loss of porosity is different in terms of burial history, the present porosity cannot reflect porosity during the accumulation period. Similar/y, high porosity during the accumulation period does not indicate that tbe present porosity is high. 2） The present reservoir location is consistent with the distribution of high paleoporosity during the accumulation period. This result indicates that high porosity belts are prone to hydrocarbon accumulation because of the dominant migration pathways generated as a result of property discrepancies under similar fault conduit conditions. Consequently, the hydrocarbon mainly accumulates in high porosity belts. Paleoporosity during the accumulation period is found to be a vital controlling factor. Therefore, high paleoporosity sandstones in the middle Es3 member of the Niuzhuang Sag have great potential for future exploration.展开更多
In order to understand the origin and flow of formation water and to evaluate the hydrocarbon accumulation and preservation conditions, the properties of formation water chemistry and dynamics of the Zhenwu area in th...In order to understand the origin and flow of formation water and to evaluate the hydrocarbon accumulation and preservation conditions, the properties of formation water chemistry and dynamics of the Zhenwu area in the southern Gaoyou Sag, North Jiangsu Basin, China, have been investigated. The results show that Xuzhuang oilfield is infiltrated discontinuously by meteoric water under gravity, which consequently leads to the desalination of formation water. Formation water in the Zhenwu and Caozhuang oilfields is less influenced by meteoric water infiltration, and the origin is interpreted to be connate water. Hydrocarbon migration, accumulation and preservation are closely related to the hydrodynamic field of formation water. Formation water concentrates gradually during the process of centrifugal flow released by mudstone compaction and the centripetal flow of meteoric water infiltration, leading to the high salinity of the central part. The geological conditions of the southern fault-terrace belt are poor for hydrocarbon accumulation and preservation as meteoric water infiltration, leaching and oxidation, while the central part, i.e., northern Zhenwu and Caozhuang oilfields is beneficial for an abundance of hydrocarbon accumulation. Most of the large scale oil-~as fields locate herein.展开更多
基金Supported by the the National Natural Science Foundation of China(U24B2017)。
文摘The Mesozoic volcanic rocks of the Bodong Low Uplift in the Bohai Bay Basin have been studied and explored for years.In 2024,the LK7-A well drilled in this region tested high-yield oil and gas flows from volcanic weathered crust.These volcanic rocks need to be further investigated in terms of distribution patterns,conditions for forming high-quality reservoirs,and main factors controlling hydrocarbon accumulation.Based on the logging,geochemical and mineralogical data from wells newly drilled to the Mesozoic volcanic rocks in the basin,and high-resolution 3D seismic data,a comprehensive study was conducted for this area.The research findings are as follows.First,the volcanic rocks in the LK7-A structure are adakites with a large source area depth,and the deep and large faults have provided channels for the emplacement of intermediate-acidic volcanic rocks.Second,volcanic rock reservoirs are mainly distributed in tectonic breccias and intermediate-acidic lavas,and they are dominantly fractured-porous reservoirs,with high-porosity and low-permeability or medium-porosity and low-permeability.Third,the dominant lithologies/lithofacies is the basic condition for forming large-scale volcanic rock reservoirs.Structural fractures and late-stage strong weathering are crucial mechanisms for the formation scale of reservoirs in the Mesozoic volcanic rocks.Fourth,the Bodong Low Uplift exhibits strong hydrocarbon charging by two sags and overpressure mudstone capping,which are favorable for forming high-abundance oil and gas reservoirs.The Mesozoic volcanic buried hills in the study area reflect good trap geometry,providing favorable conditions for large-scale reservoir formation,and also excellent migration and accumulation conditions.Areas with long-term exposure of intermediate-acidic volcanic rocks,particularly in active structural regions,are the key targets for future exploration.
基金Supported by the National Science and Technology Major Project of China(2024ZD1400101)China National Key Research and Development Project(2022YFF0801204)Major Science and Technology Project of CNPC(2023ZZ15YJ01,2021DJ0702)。
文摘Guided by the fundamental principles of the whole petroleum system,the control of tectonism,sedimentation,and diagenesis on hydrocarbon accumulation in a rifted basin is studied using the data of petroleum geology and exploration of the second member of the Paleogene Kongdian Formation(Kong-2 Member)in the Cangdong Sag,Bohai Bay Basin,China.It is clarified that the circle structure and circle effects are the marked features of a continental fault petroliferous basin,and they govern the orderly distribution of conventional and unconventional hydrocarbons in the whole petroleum systems of the rifted basin.Tectonic circle zones control sedimentary circle zones,while sedimentary circle zones and diagenetic circle zones control the spatial distribution of favorable reservoirs,thereby determining the orderly distribution of hydrocarbon accumulations in various circles.A model for the integrated,systematic accumulation of conventional and unconventional hydrocarbons under a multi-circle structure of the whole petroleum system of continental rifted basin has been developed.It reveals that each sag of the rifted basin is an independent whole petroleum system and circle system,which encompasses multiple orderly circles of conventional and unconventional hydrocarbons controlled by the same source kitchen.From the outer circle to the middle circle and then to the inner circle,there is an orderly transition from structural and stratigraphic reservoirs,to lithological and structural-lithological reservoirs,and finally to tight oil/gas and shale oil/gas enrichment zones.The significant feature of the whole petroleum system is the orderly control of hydrocarbons by multi-circle stratigraphic coupling,with the integrated,orderly distribution of conventional and unconventional reserves being the inevitable result of the multi-layered interaction within the whole petroleum system.This concept of multi-circle stratigraphic coupling for the orderly,integrated accumulation of conventional and unconventional hydrocarbons has guided significant breakthroughs in the overall,three-dimensional exploration and shale oil exploration in the Cangdong Sag.
基金Supported by the CNPC Major Science and Technology Project(2023ZZ07).
文摘Based on the achievements and research advances in oil and gas exploration in the Persian Gulf Basin,this study analyzes the orderliness of oil and gas distribution and main controlling factors of hydrocarbon accumulation with reservoir-forming assemblage as the unit.In the Persian Gulf Basin,the hydrocarbon-generating centers of source rocks of different geological ages and the hydrocarbon rich zones migrate in a clockwise direction around the Ghawar Oilfield in the Central Arabian Subbasin.Horizontally,the overall distribution pattern is orderly,showing“oil in the west and gas in the east”,and“large oil and gas fields dense in the basin center and sparse at the basin edges”.Vertically,the extents of petroleum system compounding and sources mixing increase from west to east,the pattern of tectonic strength(weak in the west and strong in the east)forming the distribution characteristics of“gas rich in the Paleozoic,oil rich in the Mesozoic,and both oil and gas rich in the Cenozoic”.The large scale accumulation and orderly distribution of oil and gas in the Persian Gulf Basin are controlled by three factors:(1)Multiple sets of giant hydrocarbon kitchens provide a resource base for near-source reservoir-forming assemblages.The short-distance lateral migration determines the oil and gas enrichment in and around the distribution area of effective source rocks.(2)The anhydrite caprocks in the platform area are thin but have experienced weak late-stage tectonic activities.Their good sealing performance makes it difficult for oil and gas to migrate vertically to shallow layers through them.The thrust faults and high-angle fractures formed by intense tectonic activities of the Zagros Orogenic Belt connect multiple source-reservoir assemblages.However,the Neogene Gachsaran Formation gypsum-salt rocks are thick and highly plastic,generally with good sealing performance,so large-scale oil and gas accumulations are still formed beneath the salt;(3)Each set of reservoir-forming assemblages is well matched in time and space in terms of the development of source rocks and reservoir-caprock assemblages,the maturation and hydrocarbon generation of source rocks,and the formation of traps,thus resulting in abundant multi layer hydrocarbon accumulations.At present,the Persian Gulf Basin is still in the stage of structural trap exploration.The pre-salt prospective traps in effective hydrocarbon kitchens remain the first choice.The areas with significant changes in Mesozoic sedimentary facies have the conditions to form large scale lithologic oil and gas reservoirs.The deep Paleozoic conventional oil and gas reservoirs and the Lower Silurian Qusaiba Member shale gas have great exploration potential and are expected to become important reserve growth areas in the future.
基金Supported by the National Natural Science Foundation of China(U23B20154,42372169).
文摘Focusing on the geochronological issues related to the matching relationship between the strike-slip fault activity and the stages of hydrocarbon generation,reservoir formation,and hydrocarbon accumulation,this study aims to quantitatively constrain the tectonic-burial history,hydrocarbon generation history,reservoir porosity evolution history,and hydrocarbon accumulation history by determining the isotopic ages and temperatures of multiphase calcites(particularly the calcites which contain hydrocarbon-bearing fluid inclusions)and quartzs filling the fractures in the Ordovician strata within the non-foreland area of Tarim Basin.Three major findings have been obtained.(1)According to the tectonic-burial history restored under the constraint of the isotopic ages and temperatures,the non-foreland area of the Tarim Basin experienced a continuous burial process during the Cambrian-Ordovician period,with only a minor uplift at the end of the Silurian.Overall,the area was characterized by continuous hydrocarbon generation and a gradual increase in vitrinite reflectance(Ro).(2)While mechanical compaction and pressure-solution during burial progressively reduced the matrix porosity,the strike-slip fault activity during the Middle Caledonian Ⅱ and Ⅲ episodes induced physical fragmentation,which created extensive interbreccia pores,fault cavities,and structural fractures as seepage pathways for surface runoff,and,in conjunction with interlayer karstification,led to the development of widespread dissolution vugs.The formation of fracture-vug system in the Ordovician limestone provided effective storage space for hydrocarbons generated during the Late Caledonian and subsequent periods.(3)The Ordovician fault-karst limestone reservoirs underwent four stages of hydrocarbon accumulation:low-medium maturity liquid hydrocarbons during the Middle-Late Caledonian,medium-high maturity liquid hydrocarbons during the Middle-Late Hercynian,high maturity liquid hydrocarbons during the Indosinian,and high-over maturity gas during the Middle Yanshanian.Variations in hydrocarbon accumulation among different strike-slip faults or different segments of the same fault are controlled by differences in source rock maturity across structural units,as well as by the timing of fault activity and fault-related connectivity to hydrocarbon sources.This research also establishes a geochronological framework for investigating strike-slip faultcontrolled reservoir formation and hydrocarbon accumulation,facilitating a more accurate determination of the reservoir formation and hydrocarbon accumulation stages,and providing critical insights for evaluating hydrocarbon enrichment zones in fault-controlled reservoirs.
基金Supported by CNPC Basic Technology Research and Development Project(2021DJ2203)National Science and Technology Major Project for New Oil and Gas Exploration and Development(2025ZD1400200).
文摘Based on the investigation of sedimentary filling characteristics and pool-forming factors of the Mesozoic in the Ordos Basin,the whole petroleum system in the Mesozoic is divided,the migration&accumulation characteristics and main controlling factors of conventional-unconventional hydrocarbons are analyzed,and the whole petroleum system model is established.First,the whole petroleum system developed in the Mesozoic takes the high-quality source rocks of the 7th member of the Triassic Yanchang Formation as the core and mainly consists of low-permeability and unconventional oil and gas reservoirs.It can be divided into four hydrocarbon accumulation domains,including intra-source retained hydrocarbon accumulation domain,near-source tight hydrocarbon accumulation domain,far-source conventional hydrocarbon accumulation domain and transitional hydrocarbon accumulation domain,which together form a continuous,symbiotic,and orderly accumulation entity wherein unconventional resources significantly outweigh conventional ones in proportion.Second,the spatial core area of sedimentary filling is the oil-rich core of the whole petroleum system.From the core to the periphery,the reservoir type evolves as shale oil→tight oil→conventional oil,the accumulation power is dominated by overpressure→buoyancy or overpressure and capillary force,the accumulation scale changes from extensive hundreds of millions of tons to a isolated hundreds of thousands-million of tons,and the gas-oil ratio and methane content decrease.Third,the sedimentary filling system provides the material basis and spatial framework for the whole petroleum system,the superimposed sand body,fault and unconformity constitute the dominant migration pathway of hydrocarbons in the far-source conventional hydrocarbon accumulation domain and the transitional hydrocarbon accumulation domain,the high-quality source rocks provide a solid resource basis for shale oil,and the micro-nano pore throat-fracture network constitute unconventional accumulation space.The hydrocarbon migration and accumulation process is mainly controlled by intense expulsion of hydrocarbon under overpressure in the pool-forming stage and the in-situ re-enrichment controlled by underpressure in post-pool-forming stage.The oil-gas enrichment and long-term preservation depends on the coordination among three factors(stable geological structure,multi-cycle sedimentation,and dual self-sealing).Fourth,the whole petroleum system model is defined as four domains,overpressure+underpressure drive,and dual self-sealing.
文摘There are abundant hydrothermal events within the Dengying Formation dolomite of the Precambrian system in southwest China.Methods including petrography identification,fluid-inclusion observation,in-situ U-Pb dating,and in-situ measurement of rare earth element(REE),etc.are integrated to characterize hydrothermal activity process within the Dengying Formation dolomite.The hydrothermal activity therein can be divided into four stages on the basis of in-situ U-Pb dating results of saddle dolomite cements.The 1st-stage(415.0-400.0 Ma)and 2nd-stage(259.4-248.0 Ma)hydrothermal events are characterized by saddle dolomite filling along the margin of fractures,or filling within dilational breccia and zebra textures.Compared with matrix dolomite and seawater-derived fibrous dolomite,saddle dolomite exhibits obvious negative anomalies of Ce elements.The 3rd-stage(225.6-199.0 Ma)hydrothermal event is represented by galena,sphalerite and other Mississipppi Valley-type(MVT)mineral cements in residual space.The formation of lead-zinc ore is due to the precipitation of metal sulfide caused by the thermo-chemical sulfate reduction(TSR)reaction between hydrothermal fluids and hydrocarbons during the large-scale hydrocarbon charging period.The 4th-stage(130.0-41.0 Ma)hydrothermal event is characterized by quartz and a small amount of fluorite filling the residual pores with dolomites.Quartz and fluorite record the migration of deep high-temperature hydrothermal fluid along early fractures and residual pores.During this period,the hydrothermal fluids result in the heterogeneous structure of bitumen,which is a clear response to high-temperature hydrothermal activity.
基金Supported by the National Natural Science Foundation of China(92255302)Science and Technology Project of PetroChina Company Limited(2023ZZ07).
文摘Based on two-dimensional/three-dimensional seismic and logging data,combined with the analysis of low-temperature thermochronology data,the unconformity surface characteristics and the patterns and dynamic mechanisms of inverted structures in the Doseo Basin in the Central and West African rift systems are systematically analyzed.Seismic profiles reveal two key inversion unconformable surfaces in the basin,i.e.the T_(5)interface within the Upper Cretaceous and the T_(4)interface at the top of the Cretaceous,which control the development of inverted structures in the basin.Four types of inverted structures,i.e.fault-associated,thrust,fold,and back-shaped negative flower,are identified.Spatially,they form six inverted structural belts trending in NE-NEE direction.The thermal history simulation of apatite fission track reveals two rapid cooling events in the late Late Cretaceous(85-80 Ma,cooling by 15℃)and the Eocene-Oligocene(30-40 Ma,cooling by 35℃),corresponding respectively to the formation periods of the T_(5)and T_(4)interface.The dynamics analysis of structural inversion indicates that the structural inversion in the Late Cretaceous was controlled by the subduction and long-range compression within the Tethys Ocean in the north of African Plate,while the structural inversion in the Eocene-Oligocene was drived by the stress transmission from the African-Eurasian collision.The two events were all controlled by the continuous tectonic regulation of the intracratonic basin by the evolution of the Tethys tectonic domain.The two periods of structural inversion enhanced the efficiency of oil and gas migration by controlling the types of traps(anticline and fault-related traps)and fault activation,precisely matching the hydrocarbon generation peaks of the Lower Cretaceous source rocks in the Late Cretaceous and Eocene,thereby controlling the formation of large-scale oil and gas reservoirs in the Doseo Basin.This geological insight provides a critical basis for the theoretical research on the evolution and hydrocarbon accumulation of inverted structures in discrete strike-slip rift systems.
基金financially supported by the National Natural Science Foundation of China (Grant No. 42002133)Science Foundation of China University of Petroleum,Beijing No.2462024XKBH009+1 种基金the 2022 AAPG Foundation Grants-in-Aid ProgramChina National Postdoctoral Science Foundation(BX20240425 and 2024M753611)
文摘With the development of unconventional hydrocarbon, how to improve the shale oil and gas recovery become urgent. Therefore hydraulic fracturing becomes the key due to the complicated properties of the reservoirs. The pore structure not only plays an essential role in the formation of complex fracture networks after fracturing but also in resource accumulation mechanism analyses. The lacustrine organicrich shale samples were selected to carry out petrophysical experiments. Scanning Electron Microscopy(SEM) and X-ray Diffraction were performed to elucidate the geology characteristics. MICP, 2D NMR, CT,and N2adsorption were conducted to classify the pore structure types. The contribution of pore structure to oil accumulation and hydrocarbon enrichment was explained through the N2adsorption test on the original and extracted state and 2D NMR. The results show that micropores with diameter less than20 nm are well-developed. The pore structure was divided into three types. Type Ⅰ is characterized by high porosity, lower surface area, and good pore throat connectivity, with free oil existing in large pores,especially lamellation fractures. The dominant nano-pores are spongy organic pores and resources hosted in large pores have been expelled during high thermal evolution. The content of nano-pores(micropores) increases and the pore volume decreases in Type Ⅱ pore structure. In addition, more absorbed oil was enriched. The pore size distribution of type Ⅱ is similar to that of type Ⅰ. However, the maturity and hydrocarbon accumulation is quite different. The oil reserved in large pores was not expelled attributed to the relatively low thermal evolution compared with type Ⅰ. Structural vitrinite was observed through SEM indicating kerogen of type Ⅲ developed in this kind of reservoir while the type of kerogen in pore structure Ⅰ is type Ⅱ. Type Ⅲ pore structure is characterized by the largest surface area,lowest porosity, and almost isolated pores with rarely free oil. Type Ⅰ makes the most contribution to hydrocarbon accumulation and immigration, which shows the best prospect. Of all of these experiments,N2adsorption exhibits the best in characterizing pores in shales due to its high resolution for the assessment of nano-scale pores. MICP and NMR have a better advantage in characterizing pore space of sandstone reservoirs, even tight sandstone reservoirs. 2D NMR plays an essential role in fluid recognition and saturation calculation. CT scanning provides a 3D visualization of reservoir space and directly shows the relationship between pores and throats and the characteristics of fractures. This study hopes to guide experiment selection in pore structure characterization in different reservoirs. This research provides insight into hydrocarbon accumulation of shales and guidance in the exploration and development of unconventional resources, for example for geothermal and CCUS reservoirs.
基金funded by the Natural Science Foundation of Heilongjiang Province (LH 2022D013)supported by the Central Support Program for Young Talents in Local Universities in Heilongjiang Province (14011202101)Key Research and Development Plan Project of Heilongjiang Province (JD22A022)。
文摘The Pinghu slope belt in the Xihu sag of the East China Sea Shelf Basin(ECSSB) is a crucial hydrocarbon production area in eastern China. However, due to the complex geological conditions, publications have lacked comprehensive research on the spatial-temporal coupling relationships of primary factors that impact hydrocarbon accumulation in the Pinghu slope belt. Furthermore, the hydrocarbon distribution patterns and the controlling factors across different study areas within the same slope belt are not yet fully understood. This study extensively utilized three-dimensional seismic data, well logging data,geochemical analysis, fluorescence analysis, and oil testing and production data to address these issues.Following a “stratification and differentiation” approach, the study identified seven distinct hydrocarbon migration and accumulation units(HMAU) in the Pinghu slope area based on the structural morphology characteristics, hydrocarbon source-reservoir-cap rock patterns, hydrocarbon migration pathways, and hydrocarbon supply range. Detailed analysis was conducted to examine the hydrocarbon distribution patterns and controlling factors within each migration and accumulation unit across different structural units, including high, medium, and low structural components. All data sources support a “southern-northern sub-area division, eastern-western sub-belt division, and variations in hydrocarbon accumulation” pattern in the Pinghu slope belt. The degree of hydrocarbon accumulation is controlled by the factors of structural morphology, hydrocarbon generation potential of source rocks, the spatial position of source slopes, fault sealing capacity, and sand body distribution. Furthermore, different coupling patterns of faults and sand bodies play a pivotal role in governing hydrocarbon enrichment systems across various migration and accumulation units. These observations indicate that three hydrocarbon accumulation patterns have been established within the slope belt, including near-source to far-source gentle slope with multiple hydrocarbon kitchens in the XP1-XP4 zones, near-source to middle-source gentle slope with dual-hydrocarbon kitchens in the XP5 zone, and near-source steep slope with a single hydrocarbon kitchen in the XP6-XP7 zones. These findings contribute to enhancing the theoretical system of hydrocarbon accumulation in the slope belt.
基金supported by the Foundation Projectof State Key Laboratory of Petroleum Resources and Prospecting (PRPDX2008-05)the "973" National Key Basic Research Program (2006CB202308)
文摘The hydrocarbon accumulation coefficient is a key parameter in resources evaluation by genetic techniques. Methods of obtaining its value scientifically have always been an important factor influencing evaluation credibility. In this paper, the hydrocarbon accumulation system is evaluated quantitatively by establishing a hierarchy structure model based on an analytical hierarchy process. The hydrocarbon accumulation system of a higher exploration degree is selected as a calibration area and its hydrocarbon accumulation coefficient can be calculated using methods of hydrocarbon generation potential and reservoir-scale sequence. The hydrocarbon accumulation coefficient of a petroleum accumulation system can be gained by analogy of reservoir forming comprehensive evaluation results with the calibration area. The hydrocarbon accumulation coefficient of each petroleum accumulation system in the upper reservoir-forming combination of the Liaohe Western Sag can be obtained with this method. Practice shows that using the analytical hierarchy process to quantitatively evaluate the hydrocarbon accumulation system and then quantitatively predict the hydrocarbon accumulation coefficient decreases the influence of human factors in resources evaluation, and makes the resources assessment more objective and closer to the actual geological condition.
基金Supported by the PetroChina Oil&Gas and New Energy Company Project(2022KT0405)PetroChina Science and Technology Major Project(2021DJ0605)Basic and Prospective Science and Technology Project of Petrochina Science and Technology Management Department(2021DJ0404).
文摘According to the latest drilling and the analysis of the burial history,source rock evolution history and hydrocarbon accumulation history,the sub-source hydrocarbon accumulation characteristics of the Permian reservoirs in the Jinan Sag,eastern Junggar Basin,are clarified,and the hydrocarbon accumulation model of these reservoirs is established.The results are obtained in four aspects.First,the main body of the thick salified lake basin source rocks in the Lucaogou Formation has reached the mature stage with abundant resource base.Large-scale reservoirs are developed in the Jingjingzigou,Wutonggou and Lucaogou formations.Vertically,there are multiple sets of good regional seals,the source-reservoir-caprock assemblage is good,and there are three reservoir-forming assemblages:sub-source,intra-source and above-source.Second,dissolution,hydrocarbon charging and pore-preserving effect,and presence of chlorite film effectively increase the sub-source pore space.Oil charging is earlier than the time when the reservoir becomes densified,which improves the efficiency of hydrocarbon accumulation.Third,buoyancy and source-reservoir pressure difference together constitute the driving force of oil charging,and the micro-faults within the formation give the advantage of"source-reservoir lateral docking"under the source rock.Microfractures can be critical channels for efficient seepage and continuous charging of oil in different periods.Fourth,the Jingjingzigou Formation experienced three periods of oil accumulation in the Middle-Late Permian,Middle-Late Jurassic and Late Neogene,with the characteristics of long-distance migration and accumulation in early stage,mixed charging and accumulation in middle stage and short-distance migration and high-position accumulation in late stage.The discovery and theoretical understanding of the Permian reservoirs in the Jinan Sag reveal that the thrust belt has good conditions for forming large reservoirs,and it is promising for exploration.The study results are of guidance and reference significance for oil and gas exploration in the Jinan Sag and other geologically similar areas.
基金the National Basic Research Program of China (973 Program, 2011CB201100)‘‘Complex hydrocarbon accumulation mechanism and enrichmentregularities of deep superimposed basins in Western China’’ National Natural Science Foundation of China (U1262205) under the guidance of related department heads and experts
文摘As petroleum exploration advances and as most of the oil-gas reservoirs in shallow layers have been explored, petroleum exploration starts to move toward deep basins, which has become an inevitable choice. In this paper, the petroleum geology features and research progress on oil-gas reservoirs in deep petroliferous basins across the world are characterized by using the latest results of worldwide deep petroleum exploration. Research has demonstrated that the deep petroleum shows ten major geological features. （1） While oil-gas reservoirs have been discovered in many different types of deep petroliferous basins, most have been discovered in low heat flux deep basins. （2） Many types of petroliferous traps are developed in deep basins, and tight oil-gas reservoirs in deep basin traps are arousing increasing attention. （3） Deep petroleum normally has more natural gas than liquid oil, and the natural gas ratio increases with the burial depth. （4） The residual organic matter in deep source rocks reduces but the hydrocarbon expulsion rate and efficiency increase with the burial depth. （5） There are many types of rocks in deep hydrocarbon reservoirs, and most are clastic rocks and carbonates. （6） The age of deep hydrocarbon reservoirs is widely different, but those recently discovered are pre- dominantly Paleogene and Upper Paleozoic. （7） The porosity and permeability of deep hydrocarbon reservoirs differ widely, but they vary in a regular way with lithology and burial depth. （8） The temperatures of deep oil-gas reservoirs are widely different, but they typically vary with the burial depth and basin geothermal gradient. （9） The pressures of deep oil-gas reservoirs differ significantly, but they typically vary with burial depth, genesis, and evolu- tion period. （10） Deep oil-gas reservoirs may exist with or without a cap, and those without a cap are typically of unconventional genesis. Over the past decade, six major steps have been made in the understanding of deep hydrocarbon reservoir formation. （1） Deep petroleum in petroliferous basins has multiple sources and many dif- ferent genetic mechanisms. （2） There are high-porosity, high-permeability reservoirs in deep basins, the formation of which is associated with tectonic events and subsurface fluid movement. （3） Capillary pressure differences inside and outside the target reservoir are the principal driving force of hydrocarbon enrichment in deep basins. （4） There are three dynamic boundaries for deep oil-gas reservoirs; a buoyancy-controlled threshold, hydrocarbon accumulation limits, and the upper limit of hydrocarbon generation. （5） The formation and distribution of deep hydrocarbon res- ervoirs are controlled by free, limited, and bound fluid dynamic fields. And （6） tight conventional, tight deep, tight superimposed, and related reconstructed hydrocarbon reservoirs formed in deep-limited fluid dynamic fields have great resource potential and vast scope for exploration. Compared with middle-shallow strata, the petroleum geology and accumulation in deep basins are more complex, which overlap the feature of basin evolution in different stages. We recommend that further study should pay more attention to four aspects： （1） identification of deep petroleum sources and evaluation of their relative contributions; （2） preservation conditions and genetic mechanisms of deep high-quality reservoirs with high permeability and high porosity; （3） facies feature and transformation of deep petroleum and their potential distribution; and （4） economic feasibility evaluation of deep tight petroleum exploration and development.
基金by the National Natural Science Foundation of China(No.U19B6003-02)the National Basic Research Program(973)of China(No.2011CB201100).
文摘The discovery of unconventional hydrocarbon resources since the late 20th century changed geologists’understanding of hydrocarbon migration and accumulations and provides a solution to energy shortage.In 2016,unconventional oil production in the USA accounted for 41%of the total oil production;and unconventional natural gas production in China accounted for 35%of total gas production,showing strong growth momentum of unconventional hydrocarbons explorations.Unconventional hydrocarbons generally coexist with conventional petroleum resources;they sometimes distribute in a separate system,not coexisting with a conventional system.Identification and prediction of unconventional resources and their potentials are prominent challenges for geologists.This study analyzed the results of 12,237 drilling wells in six representative petroliferous basins in China and studied the correlations and differences between conventional and unconventional hydrocarbons by comparing their geological features.Migration and accumulation of conventional hydrocarbon are caused dominantly by buoyance.Wepropose a concept of buoyance-driven hydrocarbon accumulation depth to describe the deepest hydrocarbon accumulation depth driven dominantly by buoyance;beyond this depth the buoyance becomes unimportant for hydrocarbon accumulation.We found that the buoyance-driven hydrocarbon accumulation depth in petroliferous basins controls the different oil/gas reservoirs distribution and resource potentials.Hydrocarbon migration and accumulations above this depth is dominated by buoyancy,forming conventional reservoirs in traps with high porosity and permeability,while hydrocarbon migration and accumulation below this depth is dominated by non-buoyancy forces(mainly refers to capillary force,hydrocarbon volumeexpansion force,etc.),forming unconventional reservoirs in tight layers.The buoyance-driven hydrocarbon accumulation depths in six basins in China range from 1200mto 4200 m,which become shallowerwith increasing geothermal gradient,decreasing particle size of sandstone reservoir layers,or an uplift in the whole petroliferous basin.The predicted unconventional resource potential belowthe buoyance-driven hydrocarbon accumulation depth in six basins in China is more than 15.71×10^(9) t oil equivalent,among them 4.71×10^(9) t reserves have been proved.Worldwide,94%of 52,926 oil and gas reservoirs in 1186 basins are conventional reservoirs and only 6%of them are unconventional reservoirs.These 94%conventional reservoirs show promising exploration prospects in the deep area below buoyance-driven hydrocarbon accumulation depth.
基金supported by the National Basic Research Program of China (No. 2012CB214805)the National Natural Science Foundation of China (Nos. 41230313, 41402119, 2017JQ0025, 41472017, 41572111)
文摘Sichuan Basin is one of the uppermost petroliferous basins in China. It experienced three evolutionary phases which were marine carbonate platform （Ediacaran to Late Triassic）, Indosinian-Yanshanian orogeny foreland basin （Late Triassic to Late Cretaceous） and uplift and tectonic modification （Late Cretaceous to Quaternary）. The present-day tectonics of the Sichuan Ba- sin and its periphery are characterized by three basic elements which are topography, basement type and surface structure, and two settings （plate margin and interior）. Therefore, be subdivided into five units which have different structure and tectonic history. The basin contains five different sets of source rocks with thickness up to 2 500 m. These source rocks were well preserved due to the presence of Middel-Lower Triassic evaporites （〉-200 m） and thick terrestrial sediments filling in the Indosinian-Yanshanian foreland basin （〉3 000 m）. The uplift and erosion since Late Cretaceous has significant influence on cross-strata migration and accumulation of oil and gas. The multi-phase evolution of the basin and its superimposed tectonic elements, good petroleum geologic conditions and diverse petroleum systems reveal its bright exploration prospects.
基金supported by the National Natural Science Foundation of China (40672086)the Ministry of Science and Technology "973" Project (2006CB701400)the Ministry of Land and Resources (XQ2004-06)
文摘The tectonic event during Cretaceous and its relationship with hydrocarbon accumulation in the Qiangtang Basin is discussed based on zircon U-Pb dating and the study of deformation, thermochronology and hydrocarbon formation. LA-ICPMS zircon U-Pb dating indicates that the tectonic event took place during the Early-Late Cretaceous （125-75Ma）. The event not only established the framework and the styles of structural traps in the basin, but also led to the cessation of the first hydrocarbon formation and the destruction of previous oil pools. The light crude oil in the basin was formed during the second hydrocarbon formation stage in the Cenozoic, and ancient structural traps formed during the Cretaceous event are promising targets for oil and gas exploration.
文摘Based on comprehensive analysis of reservoir-forming conditions, the diversity of reservoir and the difference of multistage hydrocarbon charge are the key factors for the carbonate hydrocarbon accumulation of the Ordovician in the Tarim Basin. Undergone four major deposition-tectonic cycles, the Ordovician carbonate formed a stable structural framework with huge uplifts, in which are developed reservoirs of the reef-bank type and unconformity type, and resulted in multistage hydrocarbon charge and accumulation during the Caledonian, Late Hercynian and Late Himalayan. With low matrix porosity and permeability of the Ordovician carbonate, the secondary solution pores and caverns serve as the main reservoir space. The polyphase tectonic movements formed unconformity reservoirs widely distributed around the paleo-uplifts; and the reef-bank reservoir is controlled by two kinds of sedimentary facies belts, namely the steep slope and gentle slope. The unconventional carbonate pool is characterized by extensive distribution, no obvious edge water or bottom water, complicated oil/gas/water relations and severe heterogeneity controlled by reservoirs. The low porosity and low permeability reservoir together with multi-period hydrocarbon accumulation resulted in the difference and complex of the distribution and production of oil/gas/water. The distribution of hydrocarbon is controlled by the temporal-spatial relation between revolution of source rocks and paleo-uplifts. The heterogenetic carbonate reservoir and late-stage gas charge are the main factors making the oil/ gas phase complicated. The slope areas of the paleo-uplifts formed in the Paleozoic are the main carbonate exploration directions based on comprehensive evaluation. The Ordovician of the northern slope of the Tazhong uplift, Lunnan and its periphery areas are practical exploration fields. The Yengimahalla-Hanikatam and Markit slopes are the important replacement targets for carbonate exploration. Gucheng, Tadong, the deep layers of Cambrian dolomite in the Lunnan and Tazhong-Bachu areas are favorable directions for research and risk exploration.
基金supported by the National Basic Research Program of China (973 Program, Grant No.2006CB202308)
文摘The Tarim Basin is the largest petroliferous basin in the northwest of China, and is composed of a Paleozoic marine craton basin and a Meso-Cenozoic continental foreland basin. It is of great significance in exploration of Ordovician. In over 50 years of exploration, oil and gas totaling over 1.6 billion tonnes oil-equivalent has been discovered in the Ordovician carbonate formation. The accumulation mechanisms and distribution rules are quite complicated because of the burial depth more than 3,500 m, multi-source, and multi-stage accumulation, adjustment, reconstruction and re-enrichment in Ordovician. In this paper, we summarized four major advances in the hydrocarbon accumulation mechanisms of Ordovician carbonate reservoirs. First, oil came from Cambrian and Ordovician source rocks separately and as a mixture, while natural gas was mainly cracked gas generated from the Cambrian-Lower Ordovician crude oil. Second, most hydrocarbon migrated along unconformities and faults, with different directions in different regions. Third, hydrocarbon migration and accumulation had four periods： Caledonian, early Hercynian, late Hercynian and Himalayan, and the latter two were the most important for oil and gas exploration. Fourth, hydrocarbon accumulation and evolution can be generally divided into four stages： Caledonian （the period of hydrocarbon accumulation）, early Hercynian （the period of destruction）, late Hercynian （the period of hydrocarbon reconstruction and re-accumulation）, and Himalayan （the period of hydrocarbon adjustment and re-accumulation）. Source rocks （S）, combinations of reservoir-seal （C）, paleo-uplifts （M）, structure balance belt （B） matched in the same time （T） control the hydrocarbon accumulation and distribution in the Ordovician formations. Reservoir adjustment and reconstruction can be classified into two modes of physical adjustment and variation of chemical compositions and five mechanisms. These mechanisms are occurrence displacement, biodegradation, multi-source mixing, high-temperature cracking and late gas invasion. Late hydrocarbon accumulation effects controlled the distribution of current hydrocarbon. The T-BCMS model is a basic geological model to help understanding the control of reservoirs. At present, the main problems of hydrocarbon accumulation focus on two aspects, dynamic mechanisms of hydrocarbon accumulation and the quantitative models of oil-bearing in traps, which need further systemic research.
基金financially supported by the National Natural Science Foundation of China(No.41502134)the 973 Program of China(No.2012CB214805)+1 种基金the China Postdoctoral Science Foundation(No.2014M552327)the research grant from the Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences(No.TPR-2014-02)
文摘Sichuan Basin is a typical superimposed basin, which experienced multi-phase tectonic movements, meanwhile Sinian–Cambrian underwent complex hydrocarbon accumulation processes, causing exploration difficulties in the past 60 years. Based on the microscopic evidence of fluid inclusions, combined with basin-modelling, this paper determines stages and time of hydrocarbon accumulation, reconstructs evolution of formation pressure and dynamic processes of hydrocarbon accumulation in Sinian Dengying Formation-Cambrian Longwangmiao Formation of Gaoshiti-Moxi structure. Three stages of inclusions are detected, including a stage of yellow-yellowgreen fluorescent oil inclusions, a stage of blue fluorescent oil-gas inclusions and a stage of non-fluorescent gas inclusions, reflecting the study area has experienced a series of complex hydrocarbon accumulation processes, such as formation of paleo-oil reservoirs, cracking of crude oil, formation of paleo-gas reservoirs and adjustment to present gas reservoirs, which occurred during 219–188, 192–146 and 168–0 Ma respectively. During the period of crude oil cracking, Dengying Formation-Longwangmiao Formation showed weak overpressure to overpressure characteristics, then after adjustment of paleo-gas reservoirs to present gas reservoirs, the pressure in Dengying Formation changed into overpressure but finally reduced to normal pressure system. However, due to excellent preservation conditions, the overpressure strength in Longwangmiao Formation only slightly decreased and was still kept to this day.
基金supported by the Young Scholars Development Fund of SWPU
文摘Similar reservoir sandbodies and fault conduit systems in the sandstone reservoirs in the middle Es3 member of the Niuzhuang Sag have been problematic for a long time. The following problems remain unsolved： 1） The distribution of sandstone porosity is inconsistent with the hydrocarbon accumulation. The oil sandstones have low porosity instead of high porosity. 2） Sandstones, which have the same properties, have different levels of oiliness, and the sandstones with almost the same properties show different degrees of oil-bearing capacity. This study analyzes the condition of reservoirs in the research area during the accumulation period in terms of paleoporosity estimation and discusses the critical porosity of the sandstone reservoirs during the same period. The following conclusions can be drawn from the results. 1） Although reservoir properties are low at present and some reservoirs have become tight, the paleoporosity ranging from 18% to 25% is greater than the critical porosity of 13.9%. As the： loss of porosity is different in terms of burial history, the present porosity cannot reflect porosity during the accumulation period. Similar/y, high porosity during the accumulation period does not indicate that tbe present porosity is high. 2） The present reservoir location is consistent with the distribution of high paleoporosity during the accumulation period. This result indicates that high porosity belts are prone to hydrocarbon accumulation because of the dominant migration pathways generated as a result of property discrepancies under similar fault conduit conditions. Consequently, the hydrocarbon mainly accumulates in high porosity belts. Paleoporosity during the accumulation period is found to be a vital controlling factor. Therefore, high paleoporosity sandstones in the middle Es3 member of the Niuzhuang Sag have great potential for future exploration.
基金supported jointly by the Open Fund (Grant No. PLC201105 & PLC201002) of the State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology)the National Natural Science Foundation of China (Grant No. 40839902)the National Science & Technology Major Project (Grant No. 2011ZX05005-003-008HZ & 2011ZX05002-006-003HZ)
文摘In order to understand the origin and flow of formation water and to evaluate the hydrocarbon accumulation and preservation conditions, the properties of formation water chemistry and dynamics of the Zhenwu area in the southern Gaoyou Sag, North Jiangsu Basin, China, have been investigated. The results show that Xuzhuang oilfield is infiltrated discontinuously by meteoric water under gravity, which consequently leads to the desalination of formation water. Formation water in the Zhenwu and Caozhuang oilfields is less influenced by meteoric water infiltration, and the origin is interpreted to be connate water. Hydrocarbon migration, accumulation and preservation are closely related to the hydrodynamic field of formation water. Formation water concentrates gradually during the process of centrifugal flow released by mudstone compaction and the centripetal flow of meteoric water infiltration, leading to the high salinity of the central part. The geological conditions of the southern fault-terrace belt are poor for hydrocarbon accumulation and preservation as meteoric water infiltration, leaching and oxidation, while the central part, i.e., northern Zhenwu and Caozhuang oilfields is beneficial for an abundance of hydrocarbon accumulation. Most of the large scale oil-~as fields locate herein.
