Tight sandstone reservoirs are widely developed in the Mesozoic Yanchang Formation of the Ordos Basin,China.There is a lack of understanding on the sedimentary setting,source-reservoir relationship and oil accumulatio...Tight sandstone reservoirs are widely developed in the Mesozoic Yanchang Formation of the Ordos Basin,China.There is a lack of understanding on the sedimentary setting,source-reservoir relationship and oil accumulation conditions in this area.In this study,through the comprehensive analysis of the distri-bution of tight oil,we evaluated the properties and petrological features of reservoir,geochemical characteristics of source rocks,the source-reservoir relationship,as well as the trapping,preservation and accumulation conditions of tight oil in the Chang 7 Member,and predicted the sweet spots of tight oil in the study area.The results show that the Chang 7 Member is a typical low-porosity and ultra-low permeability reservoir with great tightness,small pore throat and high capillary pressure,and must have been of near-source accumulation.The source rocks are mainly developed in the Chang 7_(3) submember,and the reservoirs mainly occur in the Chang 7_(1) and Chang 7_(2) submembers,forming a combination mode of“lower source rock and upper reservoir”.Sandbodies with good connectivity and fractures being well developed in local areas are the main hydrocarbon transport systems.The abnormal high pressure caused by hydrocarbon generation and pressurization is the main driving force of tight oil accumulation.The mode of hydrocarbon transportation is dominated by the vertical or lateral migration from under-lying source rocks or adjacent source rocks to reservoirs within a short distance.Following the integrated evaluation of lithology,physical properties and oil saturation of reservoirs and geochemical character-istics of source rocks,we grouped the sweet spots of Chang 7 Member into three types:Type I,Type II and Type III.Among others,the Type I sweet spots are the best in terms of porosity,permeability and source rock thickness and hydrocarbon enrichment which should be the focus of oilfield development.This study lays an important foundation for the economic and efficient development of tight oil in the Chang 7 Member of Heshui area,and has important implications on tight sandstone reservoirs in other regions of Ordos Basin in China.展开更多
The coal measure of Middle Jurassic Walloon Subgroup is the main reservoir of coalbed methane(CBM)reservoirs in the Surat Basin,Australia,and it is a set of typical low-rank,high-yield coal measure.To figure out the C...The coal measure of Middle Jurassic Walloon Subgroup is the main reservoir of coalbed methane(CBM)reservoirs in the Surat Basin,Australia,and it is a set of typical low-rank,high-yield coal measure.To figure out the CBM accumulation conditions and enrichment models of this coal measure,its distribution characteristics,source rock characteristics,reservoir characteristics and preservation conditions were inves-tigated based on mud logging,experimental and testing data.Then,based on the analysis results of gas origin and gas bearing property of this coal measure,3 CBM development areas in northeastern Surat Basin were analyzed and compared in terms of its gas enrichment model,and favorable conditions for CBM accumulation and enrichment of Walloon coal measure(WCM)was summarized.It is indicated that tectonic movements,groundwater conditions and macerals provide favorable conditions for gas generation of Walloon coal.The roof,floor and interbed of this coal measure are lithologically tight,presenting a good sealing capacity.Besides,the Walloon CBM reservoir is a mixed origin gas reservoir with the secondary biogenic methane as the dominant component formed in a monocline structure jointly sealed by hydrodynamic force and lithology.CBM enrichment is controlled by 3 factors,i.e.,local structure,methane generating capacity of coal bed and underground hydrodynamic force,and it can be divided into 3 models,i.e.,anticline model,syncline model and slope model,among which,the CBM enrichment degree of the former two models is higher.Finally,different from other CBM reservoirs,the Walloon CBM reservoir satisfies four favorable conditions in CBM accumulation and enrichment,including dual-carbon source,efficient methane generation,moderate hydrodynamic force and double sealing.展开更多
Up to now,the Sulige area in Ordos Basin has the favorable exploration area of 55×10^(3) km^(2),the total reserve of natural gas of nearly 6×10^(12) m^(3) and the proven reserve(including basic proven reserv...Up to now,the Sulige area in Ordos Basin has the favorable exploration area of 55×10^(3) km^(2),the total reserve of natural gas of nearly 6×10^(12) m^(3) and the proven reserve(including basic proven reserve)of 4.77×10^(12) m^(3),where the annual production of natural gas reaches 23×10^(9) m^(3),and the Sulige gasfield is the largest onshore natural gas field in China.The pay zone of the Sulige gasfield mainly is Member 8 of Shihezi Formation and Member 1 of Shanxi Formation of Permian which belong to the typical tight sandstone gas reservoir.The coal measure strata in Carboniferous Benxi Formation,Permian Taiyuan Formation and Shanxi Formation provide abundant gas sources for the Gulige gas reservoirs.An open-flow sedimentary model of lacustrine delta is developed,the gentle bottom,sand supply from multisource,strong hydrodynamic force and multi-period superposition control the distribution of largearea reservoir sand body.Lithology of the reservoir is the sandstone of the fluvial-delta facies,the physical property is poor and the heterogeneity is strong,the average porosity ranges from 4%to 12%and the average permeability varies from 0.01 to 1 mD.The gas reservoir is characterized by wide hydrocarbon generation,pervasive hydrocarbon charging,short-range migration and massive accumulation.The pressure coefficient of the gas reservoir ranges from 0.62 to 0.90,indicating the low-pressure gas reservoir,and the single-well yield is low.Full digital seismic technique in the desert area,nonlongitudinal seismic technique in the loess plateau,accurate logging evaluation technique,tight sand reservoir stimulation technology and horizontal well development technology are key technologies for exploration and development of Sulige gasfield.展开更多
The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration&development of coalbed methane(CBM),it has become the largest CBM industrializatio...The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration&development of coalbed methane(CBM),it has become the largest CBM industrialization base in China and also is a model which successfully realize commercialization of CBM of high rank coal-bearing basin in the world.Although the high-rank coal field is characterized by low pressure,low permeability,low saturation and strong heterogeneity,the exploration practice and research show that the accumulation conditions of CBM reservoir in the Qinshui Basin are superior.As main productive intervals,No.15 coal seam of Taiyuan Formation and No.3 coal seam of Shanxi Formation respectively belong to the epicontinental-sea carbonate platform sedimentary system and the epicontinental-sea shallow-water delta sedimentary system.The coal seam has large thickness,and is mostly composed of humic coal and mainly contains vitrinite.Affected by tectonic thermal events in the Yanshanian period,the coal rank is high,the adsorption capacity is strong,and the gas content is large.Formation of the CBM reservoir goes through three stages including two stages of hydrocarbon generation,gas phase transformation and sealing of hydrodynamics and roof and floor.In view of the characteristics of the Qinshui Basin topography and the high rank coal,a series of key technologies for exploration and development are developed,including mountainous region seismic acquisition,processing and interpretation technology,drilling and completion technology of multiple wells,drilling and completion technology of multiple horizontal wells dominated by compound V type,deplugging secondary fracturing stimulation technology,control technology of high rank CBM drainage,and CBM gathering and transportation technology,which effectively supports the scale and industrialization development of high rank CBM in the Qinshui Basin.展开更多
The PL 19e3 Oilfield is the only super-large monolithic oilfield with oil and gas reserves up to 1×10^(9) t in the Bohai Bay Basin,and it has been successfully developed.Exploration and development practices have...The PL 19e3 Oilfield is the only super-large monolithic oilfield with oil and gas reserves up to 1×10^(9) t in the Bohai Bay Basin,and it has been successfully developed.Exploration and development practices have provided abundant data for analyzing formation conditions of this super-large oilfield.On the basis of the exploration and development history,fundamental reservoir features,and with available geological,geophysical and test data,the hydrocarbon accumulation conditions and key exploration&development technologies of the PL 19e3 Oilfield were discussed.The key conditions for forming the super-large Neogene oilfield include four aspects.Firstly,the oilfield is located at the high position of the uplift that contacts the brachy-axis of the multi-ridge slope in the biggest hydrocarbon-rich sag in the Bohai Bay Basin,thus it has sufficient hydrocarbon source and extremely superior hydrocarbon migration condition.Secondly,the large-scale torsional anticlines which formed in the Neogene under the control of the Tanlu strike-slipping movement provide sufficient storage spaces for oil and gas preservation.Thirdly,the“multiple sets of composite reservoir-caprock assemblages”developing in the special shallow-water delta further contributes greatly to the effective storage space for oil and gas preservation.Fourthly,due to the coupling of the uplift and strike slip in the neotectonic period,extensive faulting activities constantly released the pressure while the late period massive hydrocarbon expulsion of the Bozhong took place at the same time,which assures the constant and intense charging of oil and gas.The super-large PL 19e3 Oilfield was controlled by the coupling effects of all those special geologic factors.In view of this oilfield's features(e.g.violently reformation caused by strike slip,and the special sedimentary environment of shallow-water delta),some key practical technologies for exploration and development have been developed.Such technologies include:the special prestack depth migration processing for gas cloud zones,the prediction of thin interbed reservoirs based on high-precision inversion of geologic model,the reservoir description for the shallow-water braided river delta,the quantitative description for remaining oil in the commingled oil reservoirs with wide well spacing and long well interval,and the well pattern adjustment for formations during high water cut period in the complex fluvial-facies oilfields.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
Quaternary biogenic gas reservoirs are extensively developed in the Sanhu Depression of the Qaidam Basin,where the largest domestic biogenic gas production base has been built up.In recent years,however,the exploratio...Quaternary biogenic gas reservoirs are extensively developed in the Sanhu Depression of the Qaidam Basin,where the largest domestic biogenic gas production base has been built up.In recent years,however,the exploration of biogenic gas there encounters a variety of difficulties,such as the identification of true and false seismic abnormality,the determination of micro-relief structure and the identification and description of lithologic traps,which are the bottlenecks restricting its exploration breakthrough.In this paper,hydrocarbon accumulation patterns of biogenic gas were studied.Then,based on fine structure interpretation results,combined with laboratory experiments,the sealing capacity,distribution range,formation time and genesis of salt crust were discussed,and the salt crust covered hydrocarbon accumulation pattern of biogenic gas was put forward.Finally,combined with the conditions of source rocks and reservoirs,the exploration prospect of salt crust covered biogenic gas reservoirs was predicted.And the following research results were obtained.First,the Quaternary in the Sanhu Depression is composed of sandstone-mudstone interbeds of shore-shallow lake facies,with superior conditions of source rocks and reservoirs.Many source-reservoir-caprock assemblages are vertically formed.The biogenic gas has the characteristics of dynamic hydrocarbon accumulation,i.e.,continuous migration,accumulation,diffusion and re-accumulation.Second,under the effect of Himalayan movement,the climate changes frequently and the salinity of the ancient lake is zoned in the Sanhu Depression.A freshwater area is formed at the inlet of the river in the south and a brine area is formed in the north.Under the influence of evaporation,the phreatic water in the north is salinized continuously,and a set of extensively distributed salt crust with steady thickness and a strong sealing capacity is formed at the eastern part of Lingjian fault.Third,the biogenic gas generated by dark mudstone of lacustrine facies in the depression center migrates laterally and vertically to Lingjian fault zone and gets accumulated under the sealing of salt crust.In conclusion,high-quality source rocks and reservoirs and the salt crust with a strong sealing capacity in the Sanhu Depression constitute a good spatial-temporal configuration relationship of source rocks,reservoirs and cap rocks,so salt crust covered biogenic gas reservoirs can be formed to provide abundant natural gas resources with a broad exploration prospect.展开更多
To construct a giant Sichuan gas province,it is in an urgent need of exploring new replacement areas with abundant natural gas resources and great exploration potential.In this paper,the formation conditions(e.g.sourc...To construct a giant Sichuan gas province,it is in an urgent need of exploring new replacement areas with abundant natural gas resources and great exploration potential.In this paper,the formation conditions(e.g.source rock,reservoir and play)and the distribution laws of the deep-seated old giant marine carbonate oil/gasfields in China's Craton Basins were investigated systematically.Then,the accumulation and enrichment conditions of deep Sinian natural gas in the Sichuan Basin were analyzed.Finally,potential and favorable target zones of natural gas exploration in the Dengying Formation of Upper Sinian were evaluated.And the following research results were obtained.Firstly,the effec-tiveness and scale of source kitchens,reservoirs and reservoirecaprock assemblages and the proximity are the necessary conditions for the formation of deep-seated giant carbonate oil/gasfields,and paleo-uplifts,paleo-slopes and paleo-fault zones are the favorable areas of searching deep-seated giant carbonate oil/gasfields.Secondly,in the Sichuan Basin,three sets of high-quality source rocks are developed in the NeoproterozoiceCambrian System,and their maturity of organic matter is still in the optimal window for cracking gas,so the gas generation scale is large.Thirdly,after the microbial carbonate rocks of Dengying Formation in the Sichuan Basin were reconstructed by constructive diagenesis,effective reservoirs are formed and distributed widely.Fourthly,owing to the integrated source rocks and cap rocks of Dengying Formation,the marginal platform and the intra platform have favorable conditions for proximal hydrocarbon accumulation.In conclusion,the deep Sinian in the Sichuan Basin has good conditions of hydrocarbon accumulation and it is an important replacement area of natural gas exploration.Paleo-uplifts and slopes in the central Sichuan Basin have been the favorable locations of natural gas accumulation for a long period.Large-scale exploration shall focus on four favorable areas,including the marginal platform zone in the fourth member of Dengying Formation,the marginal platform zone in the second member of Dengying Formation,the bioherm shoalbody of Dengying Formation intra platform in the paleo-uplifts and slopes of the central Sichuan Basin,and the bioherm shoalbody of Dengying Formation in the eastern Sichuan Basin.展开更多
The geological background of the fluvial and lacustrine depository system in the large mid-shallow layered depressed lake in the Songliao Basin has been proven to have the geological conditions for the formation of li...The geological background of the fluvial and lacustrine depository system in the large mid-shallow layered depressed lake in the Songliao Basin has been proven to have the geological conditions for the formation of lithologic reservoirs over a large area. Because the rise and fall of the base level caused considerable differences in the space at different periods, the types of sand bodies varied in different geologic periods; but at the same time, because of the differences in burial depths and the relative differences in positions of the siltstones and source rocks, the formation conditions and distributive regularities for oil-bearing groups of subtle reservoirs also vary accordingly. In view of the reality of the thinly-interbedded lithologic reservoir in the deltaic frontal facies belt, we have conducted a series of research to study the thinly-interbedded subtle reservoirs with the help of high resolution sequence stratigraphy, pattern recognition and the geophysical recognition and prediction techniques for thinly-interbedded subtle reservoirs, thus achieving a better effect and optimizing several exploration target areas, each of which has an oil reserve of about 100 million tons. This has shed light on further exploration of new subtle reservoirs.展开更多
This research presents the results of a comprehensive study of mineralogical and geochemical features of REE distribution in coals of Central Kazakhstan deposits—Karaganda coal basin and Shubarkol deposit,which have ...This research presents the results of a comprehensive study of mineralogical and geochemical features of REE distribution in coals of Central Kazakhstan deposits—Karaganda coal basin and Shubarkol deposit,which have large hard coal reserves and are industrially important for the coal industry of Kazakhstan;the research is based on 205 samples of clayey interlayers and coal seams.It shows basic patterns of distribution and features of concentration for impurity elements,gives an estimate of the impurity elements concentration,including REE,defines conditions and factors of their accumulation,and studies features of their forms in coal and coal-bearing rocks,which allows estimating the mechanisms of their migration and conditions of accumulation.According to the results of geochemical indicators,the article establishes the factors of REE dislocation,reveals the composition of margin rocks that have influenced REE concentration in coal seams,and the presented latest data on mineralogy allowed to establish the ways of their transportation to the paleobasin during the synand epigenetic periods of formation of the coal deposits of Central Kazakhstan being researched.It was found that the coals are insignificantly enriched with heavy lanthanides from Ho to Lu.The distribution curves of UCC normalized REE values in the coals are similar and coincide,but they are less than the average value for world coal,and amount to only one-third of the UCC.It was found that the highest concentrations of all REE are characteristic of clayey interlayers and oxidized coals.The La/Yb ratio in this case increases upwards along the section,indicating mainly clastogenic mechanism of REE delivery to the coals.In coal and clay samples,the predominant mineral form of REE is light lanthanide phosphates.Identified particles of REE from minerals and their composition peculiarities suppose autigene nature of their formation.The formation of the bulk of autigene minerals occurred during the maturation of brown coals and their transformation into hard ones.展开更多
The Sichuan Basin has abundant oil and gas resources and it has been generally acknowledged as a super petroliferous basin.In recent years,immense exploration and development potential of deep natural gas emerges in t...The Sichuan Basin has abundant oil and gas resources and it has been generally acknowledged as a super petroliferous basin.In recent years,immense exploration and development potential of deep natural gas emerges in the Sichuan Basin.The identification of strikeeslip faults and their reservoir controlling effects are of great significance to develop a new exploration domain of fault-controlled gas reservoirs.In order to clarify the distribution of strikeeslip faults in the Sichuan Basin and their relationships with natural gas exploration,in view that the strikeeslip faults in this basin are small and complex with poor seismic data and influenced more by the fold deformation of Triassic gypsum salt beds,this paper identifies strikeeslip faults and analyzes their characteristics,distribution and genesis based on the interpretation of continuous 3D seismic data of the central Sichuan Basin.Then,the fault-controlled gas reservoir model of strike-slip fault is established by reviewing old wells and evaluating geological conditions of hydrocarbon accumulation.Finally,the exploration potential and exploration direction of fault-controlled gas reservoirs are discussed.And the following research results are obtained.First,intraplate weak strikeeslip faults can be identified by combining the seismic profile marker of strikeeslip fault with the plane marker.Second,eight large strikeeslip fault zones with a total length of 1280 km are identified and confirmed in the central Sichuan Basin.Third,strikeeslip faults are mainly distributed in the SinianePermian System,mainly composed of small-displacement oblique faults and echelon faults,and different in stratification,grading,classification and segmentation.Fourth,under the control of the oblique subduction of the Proto-Tethys Ocean and the different structures of the basement,the strikeeslip faults in the central Sichuan Basin were formed in the Sinian and there are multiple stages of inherited CaledonianeHercynian activities.Fifth,the strikeeslip faults in the central Sichuan Basin play a role in sourceereservoir connection,reservoir stimulation,and gas accumulation and high yield,and constitute the fault-controlled natural gas accumulation system of“three-element controlling reservoir and composite hydrocarbon accumulation”based on source rock,fault and reservoir.In conclusion,a large intraplate strikeeslip fault system is developed in the Sichuan Basin,which has the geological conditions of hydrocarbon accumulation to form strikeeslip fault-controlled large gas field,and the large source connecting strike-slip fault zones are the main breakthrough directions of natural gas exploration in fault-controlled carbonate rocks.展开更多
The East Coast of Canada presents multiple passive continental margin basins(PCMBs)characterized by significant architectural differences and limited oil and gas discoveries,establishing these basins as the global fro...The East Coast of Canada presents multiple passive continental margin basins(PCMBs)characterized by significant architectural differences and limited oil and gas discoveries,establishing these basins as the global frontier for hydrocarbon exploration.Limited understanding of the characteristics of basin ar-chitectures and their control of hydrocarbon accumulation hinders exploration breakthroughs in these basins.Using magnetic anomaly,seismic,and drilling data,this study conducts integrated geological and geophysical interpretations of the PCMBs.Accordingly,this study reveals that the PCMBs have undergone three evolutionary stages,namely rifting(comprising three episodes),depression,and continental margin,with the synthem of each stage being referred to as rift layer,depression layer,and continental margin layer,respectively.Under the control of transform faults and basement nature,four distinct types of PCMBs have formed:transtensional,transform,gentle-rampy,and volcanic rifted types from south to north.The basins with varying architectures govern the sedimentary filling,the combination of petro-leum system elements,and differential hydrocarbon accumulation across three major types of synthems.Furthermore,this study highlights substantial hydrocarbon exploration potentials in the turbidite sandstones within the slope and basin-floor areas of the transtensional and transform types of PCMBs,as well as in the deltaic sandstones within the rift and depression layers of the gentle-rampy type of PCMBs.展开更多
The lower Cambrian Niutitang Formation is of crucial importance for shale gas target reservoirs in western Hubei,China;however,little work has been done in this field,and its shale gas accumulation and enrichment mech...The lower Cambrian Niutitang Formation is of crucial importance for shale gas target reservoirs in western Hubei,China;however,little work has been done in this field,and its shale gas accumulation and enrichment mechanism are still unclear.Based on survey wells,outcrop data,and large numbers of tests,the geological conditions of shale gas accumulation were studied;moreover,the factors that influence the gas content were thoroughly discussed.The results show that the Niutitang Formation(Є1n)can be divided into three sections:the first section(Є_(1)n^(1)),the second section(Є_(1)n^(2)),and the third section(Є1n3).TheЄ_(1)n^(2) is the main shale gas reservoir.The deep shelf facies is the main sedimentary facies and can be divided into three main lithofacies:argillaceous siltstone,carbonaceous shale and carbonaceous siliceous rock.The total organic carbon(TOC)content shows gentle growth trends until bottom of theЄ_(1)n^(2) and then decreases rapidly within theЄ_(1)n^(1),and the TOC content mainly ranges from 2%to 4%horizontally.The calcite and dolomite dissolution pores,clay intergranular pores and organic pores are the main pore types and the micropore types are clearly related to the mineral compositions and the TOC content.Vertically,the gas content is mainly affected by the TOC content.Horizontally,wells with high gas contents are distributed only southeast of the Huangling anticline,and the combination of structural styles,fault and fracture development,and the distribution of the regional unconformity boundary between the upper Sinian Dengying Formation(Z2d)and theЄ_(1)n^(2) are the three most important factors affecting the gas content.The favorable areas must meet the following conditions:a deep shelf environment,the presence of theЄ_(1)n^(1),wide and gentle folds,far from large normal faults that are more than 5 km,moderate thermal evolution,and greater than 500 m burial depth;this includes the block with the YD2–ZD2 wells,and the block with the Y1 and YD4 wells,which are distributed in the southern portion of the Huangling anticline and northern portion of the Xiannvshan fault.展开更多
China is rich in shale gas resources and has broad prospects for development. However, the quality ofshale gas resources in China is different from that in the United States, so independent unique technologies are urg...China is rich in shale gas resources and has broad prospects for development. However, the quality ofshale gas resources in China is different from that in the United States, so independent unique technologies are urgently required in China. In this regard, PetroChina has carried out theoretical andtechnical researches systematically on shale gas in Longmaxi Formation in southern Sichuan according toits geology-engineering characteristics. Guided by the “three-control” theory for marine shale gasenrichment and high yield (i.e. sedimentary diagenesis controls reservoir, preservation conditions control accumulation, and continuous thickness of Type I reservoir controls production), six key explorationand development technologies in southern China have been innovatively developed for marine shale gaswhich experienced multi-stage tectonic evolution. The technologies include comprehensive geologicalevaluation technology, development optimization technology, optimal and fast drilling technology forhorizontal well, volume fracturing technology for horizontal well, factory-like operation technology, andefficient clean production technology. These technologies have enabled the large-scale commercial recovery of shale gas. By the end of 2019, PetroChina had obtained proved geological reserves of1.06 1012 m3, had built production capacity of 10 109 m3, and had cumulative gas production of20 109 m3 in southern Sichuan. The remarkable results of application are of great significance forvigorously developing shale gas industry to reduce external dependence, ensure national energy security,and realize the strategy of "ecological priority and green development".展开更多
The Qingcheng oilfield,the largest shale oil field in China,was discovered in 2019 in source rock of Chang 7 Member of Mesozoic Yanchang Formation,Changqing Oilfield in Ordos Basin,with newly increased proven geologic...The Qingcheng oilfield,the largest shale oil field in China,was discovered in 2019 in source rock of Chang 7 Member of Mesozoic Yanchang Formation,Changqing Oilfield in Ordos Basin,with newly increased proven geological reserves of 358 million tons,predicted geological reserves of 693 million tons,and a total of 1.051 billion tons of shale oil resources.This achieves a historic breakthrough in exploration of shale oil in Chang 7 Member.In recent years,focusing on key issues,such as whether there develop sweet spots in source rock,whether commercial oil production capacity can be formed,and whether scale-effective development can be achieved,studies about geological conditions for shale oil accumulation have been continuously carried out,key supporting technologies have been developed,and a series of theoretical innovations and technological breakthroughs have been achieved in oil exploration in source rocks.The results indicate that shale oil accumulation in Chang 7 Member is controlled by following factors.Firstly,lacustrine black shale,dark mudstone and other high-quality source rocks lay a material foundation for shale oil formation.Secondly,sandy deposits intercalated within black shale and dark mudstones are exploration sweet spots,and sandbody combination types are controlled by morphology of bottom of the lacustrine basin.Thirdly,reservoir properties are good due to development of micro-nano pore throats.Finally,reservoirs with high oil saturation and high gas-oil ratio are formed due to high-intensity oil charging in source rock.Effective matching of multiple factors is a key for shale oil accumulation in Chang 7 Member in Ordos Basin.Through innovation of key supporting technologies,exploration and development technologies for shale oil are developed,and substantial breakthrough on exploration and development of shale oil is realized.The first application of logging-seismic combination technology in loess plateau improves significantly quality of 3D seismic data,which effectively guides prediction of sandy sweet spots.Three-quality well logging technology is used for further evaluation of geological and engineering sweet spots of shale oil.With volumetric fracturing technology based on precise segmentation of long horizontal wells,initial daily oil production of individual well is increased from previously 10 tons to more than 18 tons.The exploration breakthrough in source rocks in Chang 7 Member in Qingcheng oilfield provides an important resource base for the second accelerated development of Changqing Oilfield.It is predicated that oil production from shale in Chang 7 Member in Qingcheng oilfield will reach three million tons in 2022 and five million tons in 2025.展开更多
基金This work was supported by PetroChina Innovation Foundation(No.2020D-5007-0202)Opening Foundation of State Key Laboratory of Continental Dynamics,Northwest University(No.20LCD09).
文摘Tight sandstone reservoirs are widely developed in the Mesozoic Yanchang Formation of the Ordos Basin,China.There is a lack of understanding on the sedimentary setting,source-reservoir relationship and oil accumulation conditions in this area.In this study,through the comprehensive analysis of the distri-bution of tight oil,we evaluated the properties and petrological features of reservoir,geochemical characteristics of source rocks,the source-reservoir relationship,as well as the trapping,preservation and accumulation conditions of tight oil in the Chang 7 Member,and predicted the sweet spots of tight oil in the study area.The results show that the Chang 7 Member is a typical low-porosity and ultra-low permeability reservoir with great tightness,small pore throat and high capillary pressure,and must have been of near-source accumulation.The source rocks are mainly developed in the Chang 7_(3) submember,and the reservoirs mainly occur in the Chang 7_(1) and Chang 7_(2) submembers,forming a combination mode of“lower source rock and upper reservoir”.Sandbodies with good connectivity and fractures being well developed in local areas are the main hydrocarbon transport systems.The abnormal high pressure caused by hydrocarbon generation and pressurization is the main driving force of tight oil accumulation.The mode of hydrocarbon transportation is dominated by the vertical or lateral migration from under-lying source rocks or adjacent source rocks to reservoirs within a short distance.Following the integrated evaluation of lithology,physical properties and oil saturation of reservoirs and geochemical character-istics of source rocks,we grouped the sweet spots of Chang 7 Member into three types:Type I,Type II and Type III.Among others,the Type I sweet spots are the best in terms of porosity,permeability and source rock thickness and hydrocarbon enrichment which should be the focus of oilfield development.This study lays an important foundation for the economic and efficient development of tight oil in the Chang 7 Member of Heshui area,and has important implications on tight sandstone reservoirs in other regions of Ordos Basin in China.
基金Project supported by National Natural Science Foundation of China(No.41272167)S&T project of CNOOC Gas&Power Group(No.QDKY-2017-YFZX-12).
文摘The coal measure of Middle Jurassic Walloon Subgroup is the main reservoir of coalbed methane(CBM)reservoirs in the Surat Basin,Australia,and it is a set of typical low-rank,high-yield coal measure.To figure out the CBM accumulation conditions and enrichment models of this coal measure,its distribution characteristics,source rock characteristics,reservoir characteristics and preservation conditions were inves-tigated based on mud logging,experimental and testing data.Then,based on the analysis results of gas origin and gas bearing property of this coal measure,3 CBM development areas in northeastern Surat Basin were analyzed and compared in terms of its gas enrichment model,and favorable conditions for CBM accumulation and enrichment of Walloon coal measure(WCM)was summarized.It is indicated that tectonic movements,groundwater conditions and macerals provide favorable conditions for gas generation of Walloon coal.The roof,floor and interbed of this coal measure are lithologically tight,presenting a good sealing capacity.Besides,the Walloon CBM reservoir is a mixed origin gas reservoir with the secondary biogenic methane as the dominant component formed in a monocline structure jointly sealed by hydrodynamic force and lithology.CBM enrichment is controlled by 3 factors,i.e.,local structure,methane generating capacity of coal bed and underground hydrodynamic force,and it can be divided into 3 models,i.e.,anticline model,syncline model and slope model,among which,the CBM enrichment degree of the former two models is higher.Finally,different from other CBM reservoirs,the Walloon CBM reservoir satisfies four favorable conditions in CBM accumulation and enrichment,including dual-carbon source,efficient methane generation,moderate hydrodynamic force and double sealing.
基金The work was supported by the Science and Technology Major Project of PetroChina(No.2016E-05)Preliminary Project of PetroChina Exploration&Production Company(No.135YQZP-2017-KT11).
文摘Up to now,the Sulige area in Ordos Basin has the favorable exploration area of 55×10^(3) km^(2),the total reserve of natural gas of nearly 6×10^(12) m^(3) and the proven reserve(including basic proven reserve)of 4.77×10^(12) m^(3),where the annual production of natural gas reaches 23×10^(9) m^(3),and the Sulige gasfield is the largest onshore natural gas field in China.The pay zone of the Sulige gasfield mainly is Member 8 of Shihezi Formation and Member 1 of Shanxi Formation of Permian which belong to the typical tight sandstone gas reservoir.The coal measure strata in Carboniferous Benxi Formation,Permian Taiyuan Formation and Shanxi Formation provide abundant gas sources for the Gulige gas reservoirs.An open-flow sedimentary model of lacustrine delta is developed,the gentle bottom,sand supply from multisource,strong hydrodynamic force and multi-period superposition control the distribution of largearea reservoir sand body.Lithology of the reservoir is the sandstone of the fluvial-delta facies,the physical property is poor and the heterogeneity is strong,the average porosity ranges from 4%to 12%and the average permeability varies from 0.01 to 1 mD.The gas reservoir is characterized by wide hydrocarbon generation,pervasive hydrocarbon charging,short-range migration and massive accumulation.The pressure coefficient of the gas reservoir ranges from 0.62 to 0.90,indicating the low-pressure gas reservoir,and the single-well yield is low.Full digital seismic technique in the desert area,nonlongitudinal seismic technique in the loess plateau,accurate logging evaluation technique,tight sand reservoir stimulation technology and horizontal well development technology are key technologies for exploration and development of Sulige gasfield.
基金This research is supported by the National Basic Research Program of China(973 Program)(2009CB219600)National Science and Technology Major Project(2016ZX05003-002).
文摘The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration&development of coalbed methane(CBM),it has become the largest CBM industrialization base in China and also is a model which successfully realize commercialization of CBM of high rank coal-bearing basin in the world.Although the high-rank coal field is characterized by low pressure,low permeability,low saturation and strong heterogeneity,the exploration practice and research show that the accumulation conditions of CBM reservoir in the Qinshui Basin are superior.As main productive intervals,No.15 coal seam of Taiyuan Formation and No.3 coal seam of Shanxi Formation respectively belong to the epicontinental-sea carbonate platform sedimentary system and the epicontinental-sea shallow-water delta sedimentary system.The coal seam has large thickness,and is mostly composed of humic coal and mainly contains vitrinite.Affected by tectonic thermal events in the Yanshanian period,the coal rank is high,the adsorption capacity is strong,and the gas content is large.Formation of the CBM reservoir goes through three stages including two stages of hydrocarbon generation,gas phase transformation and sealing of hydrodynamics and roof and floor.In view of the characteristics of the Qinshui Basin topography and the high rank coal,a series of key technologies for exploration and development are developed,including mountainous region seismic acquisition,processing and interpretation technology,drilling and completion technology of multiple wells,drilling and completion technology of multiple horizontal wells dominated by compound V type,deplugging secondary fracturing stimulation technology,control technology of high rank CBM drainage,and CBM gathering and transportation technology,which effectively supports the scale and industrialization development of high rank CBM in the Qinshui Basin.
基金The work was supported by the National Science and Technology Major Project of China(No.2016ZX05024-003).
文摘The PL 19e3 Oilfield is the only super-large monolithic oilfield with oil and gas reserves up to 1×10^(9) t in the Bohai Bay Basin,and it has been successfully developed.Exploration and development practices have provided abundant data for analyzing formation conditions of this super-large oilfield.On the basis of the exploration and development history,fundamental reservoir features,and with available geological,geophysical and test data,the hydrocarbon accumulation conditions and key exploration&development technologies of the PL 19e3 Oilfield were discussed.The key conditions for forming the super-large Neogene oilfield include four aspects.Firstly,the oilfield is located at the high position of the uplift that contacts the brachy-axis of the multi-ridge slope in the biggest hydrocarbon-rich sag in the Bohai Bay Basin,thus it has sufficient hydrocarbon source and extremely superior hydrocarbon migration condition.Secondly,the large-scale torsional anticlines which formed in the Neogene under the control of the Tanlu strike-slipping movement provide sufficient storage spaces for oil and gas preservation.Thirdly,the“multiple sets of composite reservoir-caprock assemblages”developing in the special shallow-water delta further contributes greatly to the effective storage space for oil and gas preservation.Fourthly,due to the coupling of the uplift and strike slip in the neotectonic period,extensive faulting activities constantly released the pressure while the late period massive hydrocarbon expulsion of the Bozhong took place at the same time,which assures the constant and intense charging of oil and gas.The super-large PL 19e3 Oilfield was controlled by the coupling effects of all those special geologic factors.In view of this oilfield's features(e.g.violently reformation caused by strike slip,and the special sedimentary environment of shallow-water delta),some key practical technologies for exploration and development have been developed.Such technologies include:the special prestack depth migration processing for gas cloud zones,the prediction of thin interbed reservoirs based on high-precision inversion of geologic model,the reservoir description for the shallow-water braided river delta,the quantitative description for remaining oil in the commingled oil reservoirs with wide well spacing and long well interval,and the well pattern adjustment for formations during high water cut period in the complex fluvial-facies oilfields.
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Project supported by the Key Program of National Natural Science Foundation of China“Fundamental study on tight gas reservoir formation drying and tight gas seepage capacity improvement”(No.:51534006).
文摘Quaternary biogenic gas reservoirs are extensively developed in the Sanhu Depression of the Qaidam Basin,where the largest domestic biogenic gas production base has been built up.In recent years,however,the exploration of biogenic gas there encounters a variety of difficulties,such as the identification of true and false seismic abnormality,the determination of micro-relief structure and the identification and description of lithologic traps,which are the bottlenecks restricting its exploration breakthrough.In this paper,hydrocarbon accumulation patterns of biogenic gas were studied.Then,based on fine structure interpretation results,combined with laboratory experiments,the sealing capacity,distribution range,formation time and genesis of salt crust were discussed,and the salt crust covered hydrocarbon accumulation pattern of biogenic gas was put forward.Finally,combined with the conditions of source rocks and reservoirs,the exploration prospect of salt crust covered biogenic gas reservoirs was predicted.And the following research results were obtained.First,the Quaternary in the Sanhu Depression is composed of sandstone-mudstone interbeds of shore-shallow lake facies,with superior conditions of source rocks and reservoirs.Many source-reservoir-caprock assemblages are vertically formed.The biogenic gas has the characteristics of dynamic hydrocarbon accumulation,i.e.,continuous migration,accumulation,diffusion and re-accumulation.Second,under the effect of Himalayan movement,the climate changes frequently and the salinity of the ancient lake is zoned in the Sanhu Depression.A freshwater area is formed at the inlet of the river in the south and a brine area is formed in the north.Under the influence of evaporation,the phreatic water in the north is salinized continuously,and a set of extensively distributed salt crust with steady thickness and a strong sealing capacity is formed at the eastern part of Lingjian fault.Third,the biogenic gas generated by dark mudstone of lacustrine facies in the depression center migrates laterally and vertically to Lingjian fault zone and gets accumulated under the sealing of salt crust.In conclusion,high-quality source rocks and reservoirs and the salt crust with a strong sealing capacity in the Sanhu Depression constitute a good spatial-temporal configuration relationship of source rocks,reservoirs and cap rocks,so salt crust covered biogenic gas reservoirs can be formed to provide abundant natural gas resources with a broad exploration prospect.
基金supported by the National Major Science and Technology Project"Hydrocarbon accumulation,key techniques and target evaluation of carbon-ate rocks in Lower Paleozoic-Pre-Cambrian"(No.2016ZX05004).
文摘To construct a giant Sichuan gas province,it is in an urgent need of exploring new replacement areas with abundant natural gas resources and great exploration potential.In this paper,the formation conditions(e.g.source rock,reservoir and play)and the distribution laws of the deep-seated old giant marine carbonate oil/gasfields in China's Craton Basins were investigated systematically.Then,the accumulation and enrichment conditions of deep Sinian natural gas in the Sichuan Basin were analyzed.Finally,potential and favorable target zones of natural gas exploration in the Dengying Formation of Upper Sinian were evaluated.And the following research results were obtained.Firstly,the effec-tiveness and scale of source kitchens,reservoirs and reservoirecaprock assemblages and the proximity are the necessary conditions for the formation of deep-seated giant carbonate oil/gasfields,and paleo-uplifts,paleo-slopes and paleo-fault zones are the favorable areas of searching deep-seated giant carbonate oil/gasfields.Secondly,in the Sichuan Basin,three sets of high-quality source rocks are developed in the NeoproterozoiceCambrian System,and their maturity of organic matter is still in the optimal window for cracking gas,so the gas generation scale is large.Thirdly,after the microbial carbonate rocks of Dengying Formation in the Sichuan Basin were reconstructed by constructive diagenesis,effective reservoirs are formed and distributed widely.Fourthly,owing to the integrated source rocks and cap rocks of Dengying Formation,the marginal platform and the intra platform have favorable conditions for proximal hydrocarbon accumulation.In conclusion,the deep Sinian in the Sichuan Basin has good conditions of hydrocarbon accumulation and it is an important replacement area of natural gas exploration.Paleo-uplifts and slopes in the central Sichuan Basin have been the favorable locations of natural gas accumulation for a long period.Large-scale exploration shall focus on four favorable areas,including the marginal platform zone in the fourth member of Dengying Formation,the marginal platform zone in the second member of Dengying Formation,the bioherm shoalbody of Dengying Formation intra platform in the paleo-uplifts and slopes of the central Sichuan Basin,and the bioherm shoalbody of Dengying Formation in the eastern Sichuan Basin.
文摘The geological background of the fluvial and lacustrine depository system in the large mid-shallow layered depressed lake in the Songliao Basin has been proven to have the geological conditions for the formation of lithologic reservoirs over a large area. Because the rise and fall of the base level caused considerable differences in the space at different periods, the types of sand bodies varied in different geologic periods; but at the same time, because of the differences in burial depths and the relative differences in positions of the siltstones and source rocks, the formation conditions and distributive regularities for oil-bearing groups of subtle reservoirs also vary accordingly. In view of the reality of the thinly-interbedded lithologic reservoir in the deltaic frontal facies belt, we have conducted a series of research to study the thinly-interbedded subtle reservoirs with the help of high resolution sequence stratigraphy, pattern recognition and the geophysical recognition and prediction techniques for thinly-interbedded subtle reservoirs, thus achieving a better effect and optimizing several exploration target areas, each of which has an oil reserve of about 100 million tons. This has shed light on further exploration of new subtle reservoirs.
基金funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP13067779)。
文摘This research presents the results of a comprehensive study of mineralogical and geochemical features of REE distribution in coals of Central Kazakhstan deposits—Karaganda coal basin and Shubarkol deposit,which have large hard coal reserves and are industrially important for the coal industry of Kazakhstan;the research is based on 205 samples of clayey interlayers and coal seams.It shows basic patterns of distribution and features of concentration for impurity elements,gives an estimate of the impurity elements concentration,including REE,defines conditions and factors of their accumulation,and studies features of their forms in coal and coal-bearing rocks,which allows estimating the mechanisms of their migration and conditions of accumulation.According to the results of geochemical indicators,the article establishes the factors of REE dislocation,reveals the composition of margin rocks that have influenced REE concentration in coal seams,and the presented latest data on mineralogy allowed to establish the ways of their transportation to the paleobasin during the synand epigenetic periods of formation of the coal deposits of Central Kazakhstan being researched.It was found that the coals are insignificantly enriched with heavy lanthanides from Ho to Lu.The distribution curves of UCC normalized REE values in the coals are similar and coincide,but they are less than the average value for world coal,and amount to only one-third of the UCC.It was found that the highest concentrations of all REE are characteristic of clayey interlayers and oxidized coals.The La/Yb ratio in this case increases upwards along the section,indicating mainly clastogenic mechanism of REE delivery to the coals.In coal and clay samples,the predominant mineral form of REE is light lanthanide phosphates.Identified particles of REE from minerals and their composition peculiarities suppose autigene nature of their formation.The formation of the bulk of autigene minerals occurred during the maturation of brown coals and their transformation into hard ones.
基金Project supported by the Major Technological Project of PetroChina“Research and Application of Key Geophysical Techniques for Carbonate Rocks in Sichuan Basin”(No.:2016E-0604)the PetroChina-SWPU Technological Cooperation Project“Research on Basic Theory and Key Technology of Exploration and Development of Deep/Ultra-deep Carbonate Gas Reservoirs”(No.:2020CX010000)。
文摘The Sichuan Basin has abundant oil and gas resources and it has been generally acknowledged as a super petroliferous basin.In recent years,immense exploration and development potential of deep natural gas emerges in the Sichuan Basin.The identification of strikeeslip faults and their reservoir controlling effects are of great significance to develop a new exploration domain of fault-controlled gas reservoirs.In order to clarify the distribution of strikeeslip faults in the Sichuan Basin and their relationships with natural gas exploration,in view that the strikeeslip faults in this basin are small and complex with poor seismic data and influenced more by the fold deformation of Triassic gypsum salt beds,this paper identifies strikeeslip faults and analyzes their characteristics,distribution and genesis based on the interpretation of continuous 3D seismic data of the central Sichuan Basin.Then,the fault-controlled gas reservoir model of strike-slip fault is established by reviewing old wells and evaluating geological conditions of hydrocarbon accumulation.Finally,the exploration potential and exploration direction of fault-controlled gas reservoirs are discussed.And the following research results are obtained.First,intraplate weak strikeeslip faults can be identified by combining the seismic profile marker of strikeeslip fault with the plane marker.Second,eight large strikeeslip fault zones with a total length of 1280 km are identified and confirmed in the central Sichuan Basin.Third,strikeeslip faults are mainly distributed in the SinianePermian System,mainly composed of small-displacement oblique faults and echelon faults,and different in stratification,grading,classification and segmentation.Fourth,under the control of the oblique subduction of the Proto-Tethys Ocean and the different structures of the basement,the strikeeslip faults in the central Sichuan Basin were formed in the Sinian and there are multiple stages of inherited CaledonianeHercynian activities.Fifth,the strikeeslip faults in the central Sichuan Basin play a role in sourceereservoir connection,reservoir stimulation,and gas accumulation and high yield,and constitute the fault-controlled natural gas accumulation system of“three-element controlling reservoir and composite hydrocarbon accumulation”based on source rock,fault and reservoir.In conclusion,a large intraplate strikeeslip fault system is developed in the Sichuan Basin,which has the geological conditions of hydrocarbon accumulation to form strikeeslip fault-controlled large gas field,and the large source connecting strike-slip fault zones are the main breakthrough directions of natural gas exploration in fault-controlled carbonate rocks.
基金funded by the Major National Science and Technology Project(2016ZX05033)SINOPEC Science&Technology R&D Department's project(P21043-3)and basic research project(P22214-2 and P22214-1).
文摘The East Coast of Canada presents multiple passive continental margin basins(PCMBs)characterized by significant architectural differences and limited oil and gas discoveries,establishing these basins as the global frontier for hydrocarbon exploration.Limited understanding of the characteristics of basin ar-chitectures and their control of hydrocarbon accumulation hinders exploration breakthroughs in these basins.Using magnetic anomaly,seismic,and drilling data,this study conducts integrated geological and geophysical interpretations of the PCMBs.Accordingly,this study reveals that the PCMBs have undergone three evolutionary stages,namely rifting(comprising three episodes),depression,and continental margin,with the synthem of each stage being referred to as rift layer,depression layer,and continental margin layer,respectively.Under the control of transform faults and basement nature,four distinct types of PCMBs have formed:transtensional,transform,gentle-rampy,and volcanic rifted types from south to north.The basins with varying architectures govern the sedimentary filling,the combination of petro-leum system elements,and differential hydrocarbon accumulation across three major types of synthems.Furthermore,this study highlights substantial hydrocarbon exploration potentials in the turbidite sandstones within the slope and basin-floor areas of the transtensional and transform types of PCMBs,as well as in the deltaic sandstones within the rift and depression layers of the gentle-rampy type of PCMBs.
基金supported by the Scientific Research project of Department of Natural Resources of Hubei Province(No.ZRZY2020KJ10)Hubei Geological Bureau(No.KJ2019-3)+2 种基金the Shale Gas Geological Survey Projects of Department of Natural Resources of Hubei Province(Nos.HBCZ-17060223-170397 and DTCG-190409)We also thank the funds provided by Youth Foundation of the Northeast Petroleum University(No.2019QNL-21)Opening Fund of the Coal Reservoir Laboratory of National Engineering Research Center of CBM Development&Utilization,China University of Geosciences(Beijing)(No.2019MCQ02001)。
文摘The lower Cambrian Niutitang Formation is of crucial importance for shale gas target reservoirs in western Hubei,China;however,little work has been done in this field,and its shale gas accumulation and enrichment mechanism are still unclear.Based on survey wells,outcrop data,and large numbers of tests,the geological conditions of shale gas accumulation were studied;moreover,the factors that influence the gas content were thoroughly discussed.The results show that the Niutitang Formation(Є1n)can be divided into three sections:the first section(Є_(1)n^(1)),the second section(Є_(1)n^(2)),and the third section(Є1n3).TheЄ_(1)n^(2) is the main shale gas reservoir.The deep shelf facies is the main sedimentary facies and can be divided into three main lithofacies:argillaceous siltstone,carbonaceous shale and carbonaceous siliceous rock.The total organic carbon(TOC)content shows gentle growth trends until bottom of theЄ_(1)n^(2) and then decreases rapidly within theЄ_(1)n^(1),and the TOC content mainly ranges from 2%to 4%horizontally.The calcite and dolomite dissolution pores,clay intergranular pores and organic pores are the main pore types and the micropore types are clearly related to the mineral compositions and the TOC content.Vertically,the gas content is mainly affected by the TOC content.Horizontally,wells with high gas contents are distributed only southeast of the Huangling anticline,and the combination of structural styles,fault and fracture development,and the distribution of the regional unconformity boundary between the upper Sinian Dengying Formation(Z2d)and theЄ_(1)n^(2) are the three most important factors affecting the gas content.The favorable areas must meet the following conditions:a deep shelf environment,the presence of theЄ_(1)n^(1),wide and gentle folds,far from large normal faults that are more than 5 km,moderate thermal evolution,and greater than 500 m burial depth;this includes the block with the YD2–ZD2 wells,and the block with the Y1 and YD4 wells,which are distributed in the southern portion of the Huangling anticline and northern portion of the Xiannvshan fault.
基金The work was supported by the PetroChina Science and Technology Major Project(No.2016E-0611)National Science and Technology Major Project of China(No.2016ZX05062)Key Consulting and Research Project of Chinese Academy of Engineering(No.2018-XZ-20).
文摘China is rich in shale gas resources and has broad prospects for development. However, the quality ofshale gas resources in China is different from that in the United States, so independent unique technologies are urgently required in China. In this regard, PetroChina has carried out theoretical andtechnical researches systematically on shale gas in Longmaxi Formation in southern Sichuan according toits geology-engineering characteristics. Guided by the “three-control” theory for marine shale gasenrichment and high yield (i.e. sedimentary diagenesis controls reservoir, preservation conditions control accumulation, and continuous thickness of Type I reservoir controls production), six key explorationand development technologies in southern China have been innovatively developed for marine shale gaswhich experienced multi-stage tectonic evolution. The technologies include comprehensive geologicalevaluation technology, development optimization technology, optimal and fast drilling technology forhorizontal well, volume fracturing technology for horizontal well, factory-like operation technology, andefficient clean production technology. These technologies have enabled the large-scale commercial recovery of shale gas. By the end of 2019, PetroChina had obtained proved geological reserves of1.06 1012 m3, had built production capacity of 10 109 m3, and had cumulative gas production of20 109 m3 in southern Sichuan. The remarkable results of application are of great significance forvigorously developing shale gas industry to reduce external dependence, ensure national energy security,and realize the strategy of "ecological priority and green development".
基金supported by the National Research Council of Science and Technology Major Project of China(No.2016ZX05050,No.2017ZX05001002)National Key Basic Research Project of China(973 Program)(No.2014CB239003).
文摘The Qingcheng oilfield,the largest shale oil field in China,was discovered in 2019 in source rock of Chang 7 Member of Mesozoic Yanchang Formation,Changqing Oilfield in Ordos Basin,with newly increased proven geological reserves of 358 million tons,predicted geological reserves of 693 million tons,and a total of 1.051 billion tons of shale oil resources.This achieves a historic breakthrough in exploration of shale oil in Chang 7 Member.In recent years,focusing on key issues,such as whether there develop sweet spots in source rock,whether commercial oil production capacity can be formed,and whether scale-effective development can be achieved,studies about geological conditions for shale oil accumulation have been continuously carried out,key supporting technologies have been developed,and a series of theoretical innovations and technological breakthroughs have been achieved in oil exploration in source rocks.The results indicate that shale oil accumulation in Chang 7 Member is controlled by following factors.Firstly,lacustrine black shale,dark mudstone and other high-quality source rocks lay a material foundation for shale oil formation.Secondly,sandy deposits intercalated within black shale and dark mudstones are exploration sweet spots,and sandbody combination types are controlled by morphology of bottom of the lacustrine basin.Thirdly,reservoir properties are good due to development of micro-nano pore throats.Finally,reservoirs with high oil saturation and high gas-oil ratio are formed due to high-intensity oil charging in source rock.Effective matching of multiple factors is a key for shale oil accumulation in Chang 7 Member in Ordos Basin.Through innovation of key supporting technologies,exploration and development technologies for shale oil are developed,and substantial breakthrough on exploration and development of shale oil is realized.The first application of logging-seismic combination technology in loess plateau improves significantly quality of 3D seismic data,which effectively guides prediction of sandy sweet spots.Three-quality well logging technology is used for further evaluation of geological and engineering sweet spots of shale oil.With volumetric fracturing technology based on precise segmentation of long horizontal wells,initial daily oil production of individual well is increased from previously 10 tons to more than 18 tons.The exploration breakthrough in source rocks in Chang 7 Member in Qingcheng oilfield provides an important resource base for the second accelerated development of Changqing Oilfield.It is predicated that oil production from shale in Chang 7 Member in Qingcheng oilfield will reach three million tons in 2022 and five million tons in 2025.
