Accurate estimation of mineralogy from geophysical well logs is crucial for characterizing geological formations,particularly in hydrocarbon exploration,CO_(2) sequestration,and geothermal energy development.Current t...Accurate estimation of mineralogy from geophysical well logs is crucial for characterizing geological formations,particularly in hydrocarbon exploration,CO_(2) sequestration,and geothermal energy development.Current techniques,such as multimineral petrophysical analysis,offer details into mineralogical distribution.However,it is inherently time-intensive and demands substantial geological expertise for accurate model evaluation.Furthermore,traditional machine learning techniques often struggle to predict mineralogy accurately and sometimes produce estimations that violate fundamental physical principles.To address this,we present a new approach using Physics-Integrated Neural Networks(PINNs),that combines data-driven learning with domain-specific physical constraints,embedding petrophysical relationships directly into the neural network architecture.This approach enforces that predictions adhere to physical laws.The methodology is applied to the Broom Creek Deep Saline aquifer,a CO_(2) sequestration site in the Williston Basin,to predict the volumes of key mineral constituents—quartz,dolomite,feldspar,anhydrite,illite—along with porosity.Compared to traditional artificial neural networks (ANN),the PINN approach demonstrates higher accuracy and better generalizability,significantly enhancing predictive performance on unseen well datasets.The average mean error across the three blind wells is 0.123 for ANN and 0.042 for PINN,highlighting the superior accuracy of the PINN approach.This method reduces uncertainties in reservoir characterization by improving the reliability of mineralogy and porosity predictions,providing a more robust tool for decision-making in various subsurface geoscience applications.展开更多
The physical properties of hydrocarbon reservoirs are important factors affecting the percolation ability of the reservoirs.Tight-sand reservoirs exhibit complex pore throat connectivity due to the extensive developme...The physical properties of hydrocarbon reservoirs are important factors affecting the percolation ability of the reservoirs.Tight-sand reservoirs exhibit complex pore throat connectivity due to the extensive development of micro-and nano-scale pore and throat systems.Characterizing the microscopic properties of these reservoirs using nondestructive,quantitative methods serves as an important means to determine the characteristics of microscopic pores and throats in tight-sand reservoirs and the mechanism behind the influence of these characteristics on reservoir porosity and permeability.In this study,a low-permeability sandstone sample and two tight sandstone samples collected from the Ordos Basin were nondestructively tested using high-resolution nano-CT technology to quantitively characterize their microscopic pore throat structures and model them three-dimensionally(in 3D)based on CT threshold differences and gray models.A thorough analysis and comparison reveal that the three samples exhibit a certain positive correlation between their porosity and permeability but the most important factor affecting both porosity and permeability is the microscopic pore throat structure.Although the number of pores in tight sandstones shows a minor impact on their porosity,large pores(more than 20μm)contribute predominantly to porosity,suggesting that the permeability of tight sandstones is controlled primarily by large pore throats.For these samples,higher permeability corresponds to larger average throat sizes.Therefore,throats with average radii greater than 2μm can significantly improve the permeability of tight sandstones.展开更多
Key technologies that make productivity increase are revealed through analyzing the best practices and production data in major shale basins of North America.Trends of the key technologies and optimization designs for...Key technologies that make productivity increase are revealed through analyzing the best practices and production data in major shale basins of North America.Trends of the key technologies and optimization designs for shale oil and gas development are summarized and analyzed based on drilling and completion operations and well data.These technologies mainly include:(1)Optimizing well design and hydraulic fracturing design,including reducing cluster spacing,increasing proppant and fracturing fluid volumes,optimizing horizontal well lateral length and fracture stage length.The most effective method is to reduce cluster spacing to an optimized length.The second most effective method is to optimally increase proppant volumes.(2)Placing horizontal wells in the sweet spots and drilling the wells parallel or close to the minimum horizontal stress direction.(3)Using cube development with optimized well spacing to maximize resource recovery and reduce well interferences.Plus,in-situ stress impacts on hydraulic fracture propagation and hydrocarbon production are addressed.Determination of formation breakdown pressure is studied by considering the impacts of in-situ stresses,drilling and perforation directions.Whether or not the hydraulic fracturing can generate orthogonal fracture networks is also discussed.The key technologies and optimization design parameters proposed in this paper can be applied to guide new well placement,drilling and completion designs,and hydraulic fracture operations to increase productivity.展开更多
Tectonic activities significantly impact deep reservoir properties via sedimentary and diagenetic processes,and this is particularly true for lacustrine rift basins.The tectonic-sedimentary-diageneticreservoir system ...Tectonic activities significantly impact deep reservoir properties via sedimentary and diagenetic processes,and this is particularly true for lacustrine rift basins.The tectonic-sedimentary-diageneticreservoir system is crucial in deep reservoir exploration.This study examined the first member and upper submember of the second member of the Dongying Formation in the Bodong Low Uplift in the Bohai Bay Basin(East China),documenting the petrologic features and physical properties of reservoirs in different tectonic sub-units through integrated analysis of log and rock data,along with core observation.A mechanism for deep reservoir formation in lacustrine rift basins was developed to elucidate the sedimentary and diagenetic processes in complex tectonic settings.The results show that tectonic activities result in the occurrence of provenances in multiple directions and the existence of reservoirs at varying burial depths,as well as the significant diversity in sedimentary and diagenetic processes.The grain sizes of the sandstones,influenced by transport pathways rather than the topography of the sedimentary area,exhibit spatial complexity due to tectonic frameworks,which determine the initial pore content of reservoirs.However,the burial depth,influenced by subsequent tectonic subsidence,significantly impacts pore evolution during diagenesis.Based on the significant differences of reservoirs in slope zone,low uplift and depression zone,we establish different tectonic-diagenetic models in deep complex tectonic units of lacustrine rift basins.展开更多
Gas-bearing shales have become a major source of future natural gas production worldwide.It has become increasingly urgent to develop a reliable prediction model and corresponding workflow for identifying shale gas sw...Gas-bearing shales have become a major source of future natural gas production worldwide.It has become increasingly urgent to develop a reliable prediction model and corresponding workflow for identifying shale gas sweet spots.The formation of gas-bearing shales is closely linked to relative sealevel changes,providing an important approach to predicting sweet spots in the Wufeng-Longmaxi shale in the southern Sichuan Basin,China.Three types of marine shale gas sweet spots are identified in the shale based on their formation stages combined with relative sea-level changes:early,middle,and late transgression types.This study develops a prediction model and workflow for identifying shale gas sweet spots by analyzing relative sea-level changes and facies sequences.Predicting shale gas sweet spots in an explored block using this model and workflow can provide a valuable guide for well design and hydraulic fracturing,significantly enhancing the efficiency of shale gas exploration and development.Notably,the new prediction model and workflow can be utilized for the rapid evaluation of the potential for shale gas development in new shale gas blocks or those with low exploratory maturity.展开更多
CO_(2) flooding is a widely recognized method for enhanced oil recovery(EOR).This study aims to develop an accurate prediction method for determining the location and migration pathway of CO_(2) front,which plays an e...CO_(2) flooding is a widely recognized method for enhanced oil recovery(EOR).This study aims to develop an accurate prediction method for determining the location and migration pathway of CO_(2) front,which plays an essential role in designing effective CO_(2) injection schemes and optimizing production strategies.Given the challenges of directly monitoring CO_(2) front movement in subsurface reservoirs,numerical well testing serves as an effective tool for indirectly inferring the location and migration characteristics of the CO_(2) front.This study established a numerical well-testing model based on a compositional framework to characterize interactions among multiple components during CO_(2) flooding.The methodology used in this model involves generating well-testing curves of CO_(2) flooding and then determining their flow stages based on CO_(2) distribution within reservoirs.Accordingly,a new well-testing analysis approach was proposed to determine the CO_(2) zone front and mixing zone front.This approach was applied to a pilot study of a practical oilfield,where it effectively predicted the positions of both fronts.The findings of this study reveal that the CO_(2) zone front and the mixing zone front correspond to the beginning of the first horizontal segment and the endpoint of the upward segment in the pressure derivative curve,respectively.This study introduces a cost-effective and time-efficient method for CO_(2) front monitoring,addressing the challenges of high costs and prolonged durations typically associated with CO_(2)-EOR operations.展开更多
Carbon dioxide enhanced oil recovery(CO_(2)-EOR)technology is used for oil production and CO_(2) storage in reservoirs.Methods are being constantly developed to optimize oil recovery and CO_(2) storage during the CO_(...Carbon dioxide enhanced oil recovery(CO_(2)-EOR)technology is used for oil production and CO_(2) storage in reservoirs.Methods are being constantly developed to optimize oil recovery and CO_(2) storage during the CO_(2) displacement process,especially for low-permeability reservoirs under varying geological conditions.In this study,long-core experiments and trans-scale numerical simulations are employed to examine the characteristics of oil production and CO_(2) storage.Optimal production parameters for the target reservoir are also proposed.The results indicate that maintaining the pressure at 1.04 to 1.10 times the minimum miscible pressure(MMP)and increasing the injection rate can enhance oil production in the early stage of reservoir development.In contrast,reducing the injection rate at the later stages prevents CO_(2) channeling,thus improving oil recovery and CO_(2) storage efficiency.A solution-doubling factor is introduced to modify the calculation method for CO_(2) storage,increasing its accuracy to approximately 90%.Before CO_(2) breakthrough,prioritizing oil production is recommended to maximize the economic benefits of this process.In the middle stage of CO_(2) displacement,decreasing the injection rate optimizes the coordination between oil displacement and CO_(2) storage.Further,in the late stage,reduced pressure and injection rates are required as the focus shifts to CO_(2) storage.展开更多
This research pioneers the integration of geographic information systems(GIS)and 3D modeling within a virtual reality(VR)framework to assess the viability and planning of a 20 MW hybrid wind-solarphotovoltaic(PV)syste...This research pioneers the integration of geographic information systems(GIS)and 3D modeling within a virtual reality(VR)framework to assess the viability and planning of a 20 MW hybrid wind-solarphotovoltaic(PV)system connected to the local grid.The study focuses on Dakhla,Morocco,a region with vast untapped renewable energy potential.By leveraging GIS,we are innovatively analyzing geographical and environmental factors that influence optimal site selection and system design.The incorporation of VR technologies offers an unprecedented level of realism and immersion,allowing stakeholders to virtually experience the project's impact and design in a dynamic,interactive environment.This novel methodology includes extensive data collection,advanced modeling,and simulations,ensuring that the hybrid system is precisely tailored to the unique climatic and environmental conditions of Dakhla.Our analysis reveals that the region possesses a photovoltaic solar potential of approximately2400 k Wh/m^(2) per year,with an average annual wind power density of about 434 W/m^(2) at an 80-meter hub height.Productivity simulations indicate that the 20 MW hybrid system could generate approximately 60 GWh of energy per year and 1369 GWh over its 25-year lifespan.To validate these findings,we employed the System Advisor Model(SAM)software and the Global Solar Photovoltaic Atlas platform.This comprehensive and interdisciplinary approach not only provides a robust assessment of the system's feasibility but also offers valuable insights into its potential socio-economic and environmental impact.展开更多
The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and ...The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and fluid mobility due to the influences of the northeast and northwest dual provenance systems.This study performed multiple experimental analyses on nine samples from the area to determine the petrological and petrophysical properties,as well as the PTS characteristics of reservoirs in different provenance-controlled regions.On this basis,the pore-throat size distribution(PSD)obtained from high-pressure mercury injection(HPMI)was utilized to convert the NMR movable fluid T2spectrum,allowing for quantitative characterization of the full PSD and the occurrence characteristics of movable fluids.A systematic analysis was conducted on the primary controlling factors affecting fluid mobility in the reservoir.The results indicated that the lithology in the eastern and western regions is lithic arkose.The eastern sandstones,being farther from the provenance,exhibit higher contents of feldspar and lithic fragments,along with the development of more dissolution pores.The reservoir possesses good petrophysical properties,low displacement pressure,and high pore-throat connectivity and homogeneity,indicating strong fluid mobility.In contrast,the western sandstones,being nearer to the provenance,exhibit poor grain sorting,high contents of lithic fragments,strong compaction and cementation effects,resulting in poor petrophysical properties,and strong pore-throat heterogeneity,revealing weak fluid mobility.The range of full PSD in the eastern reservoir is wider than that in the western reservoir,with relatively well-developed macropores.The macropores are the primary space for occurrence of movable fluids,and controls the fluid mobility of the reservoir.The effective porosity of movable fluids(EPMF)quantitatively represents the pore space occupied by movable fluids within the reservoir and correlates well with porosity,permeability,and PTS parameters,making it a valuable parameter for evaluating fluid mobility.Under the multi-provenance system,the eastern and western reservoirs underwent different sedimentation and diagenesis processes,resulting in differential distribution of reservoir mineral components and pore types,which in turn affects the PTS heterogeneity and reservoir quality.The composition and content of reservoir minerals are intrinsic factors influencing fluid mobility,while the microscopic PTS is the primary factor controlling it.Low clay mineral content,welldeveloped macropores,and weak pore-throat heterogeneity all contribute to the storage and seepage of reservoir fluids.展开更多
China has pledged to peak carbon dioxide(CO_(2))emissions by 2030 and achieve carbon neutrality by 2060.Carbon capture and storage(CCS)will play a key role in these efforts.Over the past several years,the China Geolog...China has pledged to peak carbon dioxide(CO_(2))emissions by 2030 and achieve carbon neutrality by 2060.Carbon capture and storage(CCS)will play a key role in these efforts.Over the past several years,the China Geological Survey(CGS)has completed the Suitability Evaluation Map of CO_(2)Geological Storage in Main Sedimentary Basins in China and Adjacent Sea Regions in 2017.This map reflects the suitability of the first-and secondary-order tectonic units within sedimentary basins for cO_(2)geological storage for CCS planning.The Junggar Basin is recognized as an important region for future CCS projects.Results from a mesoscale evaluation using the volume method indicate that deep saline aquifers represent the most significant resources for CO_(2)storage,with potential ranging from 48×10^(9)to 164×10^(9)t(with a P50 value of 96×10^(9)t).The highest storage potential is identified in the central and northern parts of the basin,reaching up to 9.5×10^(6)t/km^(2)at the P50 probability level.In contrast,the hinterland,eastern,and western parts of the basin generally exhibit storage potential of below 1.0×10^(6)t/km^(2)at the same probability level.The CGs has also characterized historical CO_(2)plume migration in reservoirs at the storage site of the Shenhua CCS demonstration project and conducted numerical simulations of CO_(2)plume migration for periods of 10 and 20 years following the shutdown of the injection well.The CGS implemented a kiloton-scale pilot test on CO_(2)-enhanced water recovery(CO_(2)-EWR)in eastern Junggar,revealing that CO_(2)flooding can improve the pressure for fluid production,with the highest ratio of CO_(2)to produced fluids estimated at approximately 1.2.Besides,an observation field for natural CO_(2)leakage,covering about 930 m^(2),was built in Qinghai Province.In natural CO_(2)fields or at artificial CO_(2)injection research sites,cO_(2)leakage points are primarily related to the distribution of faults(especially fault crossing),which can serve as pathways for CO_(2)leakage.The observation field provides a natural analog to wellbore failure and offers an opportunity to further monitor CO_(2)geological storage sites.However,it has been inferred that borehole ZK10 at the observation field has become a leakage pathway due to the drilling activities,inadequate well-plugging,and abandonment procedures without considering CO_(2)corrosion.展开更多
The Penobscot Field,located within the Scotian Basin offshore Nova Scotia,Canada,represents an underexplored hydrocarbon field with potential for future development.Previous studies have been confined to specific rese...The Penobscot Field,located within the Scotian Basin offshore Nova Scotia,Canada,represents an underexplored hydrocarbon field with potential for future development.Previous studies have been confined to specific reservoir intervals without integrating multiple stratigraphic levels,and a comprehensive static reservoir characterization and volumetric assessment of the Penobscot Field has yet to be undertaken,constraining its full development evaluation.This study presents a comprehensive characte rization of the field by integrating geological,geophysical,and petrophysical datasets,leading to static hydrocarbon reserve estimation.The workflow involves seismic interpretation,structural modeling,petrophysical evaluation,and static volumetric calculations.Seismic analysis revealed a structu rally complex setting dominated by normal and inverted faults,with reservoir intervals primarily within the Missisauga Formation,which is subdivided into upper,middle,and lower units.Petro p hysical evaluation from well logs and core data identified key reservoir properties,including porosity ranging from 12 % to 28 %,permeability spanning from 1 to 1000 mD,and variable water saturations.Stochastic modeling of facies and petro p hysical attributes provided insights into lateral and ve rtical hete rogeneity.The Penobscot Field's original oil-in-place ranges from 41.6×10~6 m3 to 109.7×10~6 m3,with the Middle Missisauga sands presenting the highest reservoir potential.Fault seal analysis indicated predominantly sealing behavior in the shallow sections and semi-permeable conditions at greater depths,suggesting potential lateral migration pathways.The results underscore the field's hydrocarbon potential while emphasizing the significance of structural complexity,facies distribution,and petrophysical variability in reservoir quality,as well as its potential for future development or utilization of similar sand reservoirs for CO_(2) storage utilization.This work provides the first fully integrated static reservoir model of the Penobscot Field,offering critical insights for delineating the hydrocarbon reservoirs potential and future production strategies in the Scotian Basin.展开更多
Deep coal reservoirs(buried depth>2000 m)represent a significant yet underexploited resource for coalbed methane(CBM)production.In these reservoirs,CBM primarily exists in adsorbed and free phase,with the pore stru...Deep coal reservoirs(buried depth>2000 m)represent a significant yet underexploited resource for coalbed methane(CBM)production.In these reservoirs,CBM primarily exists in adsorbed and free phase,with the pore structure playing a critical role in gas storage and migration.The Jiaxian block in the northeastern Ordos Basin,has emerged as a key area for deep CBM exploration due to its promising resource potential.However,the pore structure characteristics of the No.8 coal seam in Jiaxian block and their implications for gas storage and production remain poorly understood.A comprehensive characterization of the No.8 coal seam's pore structure is conducted in the study using multiple methods including high-pressure mercury injection,N2/CO_(2)adsorption experiments,and integration of measured core gas content data and production history.The study results reveal that the pores can be mainly classified as vesicles and cellular pores,and the fractures are mainly static pressure fractures.Micropores(pore diameter<10 nm)dominate the pore system(accounting for more than 99%of the total specific surface area),providing important adsorption sites for gas storage.Although mesopores(pore diameter of 100-1000 nm)and macropores(pore diameter>1000 nm)account for a small proportion,they feature effective storage spaces and interconnectivity,resulting in a high proportion of free gas.Therefore,the reservoirs shows great development potential after stimulation(such as hydraulic fracturing).These findings emphasize the feasibility of large-scale and long-term development of CBM in the Jiaxian block in terms of reservoir space,gas content and production characteristics.This study serves to lay a scientific basis for its efficient exploitation.展开更多
Many new and developed oilfields are confined to carbonate reservoirs with a complex void space structure.In this study,the behavior of carbonates as a function of decreased reservoir pressure was examined.The study w...Many new and developed oilfields are confined to carbonate reservoirs with a complex void space structure.In this study,the behavior of carbonates as a function of decreased reservoir pressure was examined.The study was based on actual production data from wells rather than just on model data or results from computational experiments.Well-test data(170 well tests)and laboratory core samples(45 samples)results were used in the analysis.The problem of reservoir deformation has been compre-hensively addressed at the micro and macro levels.The effect of reservoir permeability throughout the entire reservoir volume on reservoir pressure was determined.With a decline in reservoir pressure,the permeability of fractures and pores in carbonates decreases.The deformation coefficients,which char-acterize the actual rate of decrease in permeability with decreasing reservoir pressure,were also calculated.The deformation coefficients and data from core studies using μ-CT and SEM were compared.Based on micro-CT data,the effective diameters of the voids were calculated to be 93μm,109μm,and 140μm for the Vinnikovskoe,Sofinskoe,and Sukharev fields,respectively.Based on μ-CT and SEM data,the predominant geometric shapes of the voids were assessed.The deformation coefficient of voids was found to depend on their size and geometric shape.The study's findings revealed deformation co-efficients of 0.172,0.205,and 0.748 for the Vinnikovskoe,Sofinskoe,and Sukharev fields,respectively.Maximum deformation coefficients are typical for large voids with a predominant slot-like shape.However,even with the predominance of primary spherical voids in carbonates,the permeability of voids decreases with decreasing reservoir pressure.展开更多
An enhanced geothermal system(EGS)represents a promising approach to sustainable energy generation by harnessing subsurface heat from deep geological formations with low natural permeability.Sedimentary basins-such as...An enhanced geothermal system(EGS)represents a promising approach to sustainable energy generation by harnessing subsurface heat from deep geological formations with low natural permeability.Sedimentary basins-such as the Williston Basin in North Dakota-are considered viable candidates for EGS development due to their broad geographic extent and moderate geothermal potential.Notably,depleted or non-productive oil wells within these basins offer a cost-effective opportunity for EGS implementation as they can be repurposed,thereby significantly reducing the need for new drilling.This study evaluates the feasibility of EGS deployment in McKenzie County,North Dakota.Core samples from five partially abandoned or dry oil wells associated with production from the Red River Formation were obtained from the Core Library of the North Dakota Geological Survey.These samples,spanning the entire thickness of the formation,were sectioned and polished at defined depth intervals for detailed analyses and precise measurements of key reservoir properties critical to geothermal assessment.Several parameters were analyzed to assess the geothermal viability of these wells,including formation temperature,temperature gradient,porosity,thermal conductivity,energy storage potential,and estimated power output via the Organic Rankine Cycle(ORC).The results demonstrate significant depth-dependent variations in thermal and petrophysical properties.Specifically,the depth range of 4000-4500 m is identified as a promising target for EGS stimulation since it is characterized by elevated temperatures,high thermal conductivity,favorable temperature gradients,and sufficient porosity-all essential properties for enhancing permeability through hydraulic fracturing.Furthermore,the calculated energy content and potential ORC power output at these depths indicate that effective geothermal energy extraction is technically feasible.This suggests a compelling opportunity to repurpose existing fossil energy infrastructure-such as abandoned oil wells-for renewable geothermal applications.Overall,the findings of this study underscore the potential of sedimentary formations for EGS development and contribute to advancing low-carbon,diversified energy solutions in alignment with national decarbonization goals.展开更多
The Zagros Basin in southwestern Iran is a significant source of coal,with numerous coal mines operating in the region.Ensuring the stability of coal mines is crucial for safe and efficient mining operations.This stud...The Zagros Basin in southwestern Iran is a significant source of coal,with numerous coal mines operating in the region.Ensuring the stability of coal mines is crucial for safe and efficient mining operations.This study investigates the time-varying response of rocks and roof resistance in coal mines in the Zagros Mountains using a novel approach that combines numerical simulation,relaxation testing,and rock displacement studies.The results show that rocks exhibit significant time-dependent behavior,with changes in rock mechanical properties over time.A comprehensive viscoelastic-plastic model is devel-oped to accurately describe the time-varying strain-softening response of rocks and simulate laboratory tests.The model integrates the Burgers and strain-softening models,simulating stress relaxation curves and rock displacement over time.The study reveals that the rock mass displays significant nonlinear behavior,with changes in rock mechanical properties over time.The findings of this study highlight the importance of considering the time-varying response of rocks and roof resistance in coal mine stability analysis.The results provide valuable insights into the time-dependent behavior of rock mass in coal mines in Iran,which can inform mining practices and mitigate potential hazards.Results in this study can contribute to developing strategies for improving roof stability and reducing the likelihood of roof collapses.展开更多
Experimental results from the Daniudi gas field enhance our understanding of mechanisms behind CO_(2) injection for enhanced recovery from tight-sand gas reservoirs.The results reveal that the diffusion coefficients o...Experimental results from the Daniudi gas field enhance our understanding of mechanisms behind CO_(2) injection for enhanced recovery from tight-sand gas reservoirs.The results reveal that the diffusion coefficients of CO_(2) in tight reservoirs range from 10-8m2/s to 10-9m2/s,correlating negatively with pore pressure and positively with pore radius.In these reservoirs,CO_(2) manifests a significantly higher adsorption capability compared to CH4,suggesting a competitive adsorption advantage.Further,the amount of adsorbed gas correlates negatively with core permeability and positively with pore pressure.In the late-stage depletion-drive development of tight-sand gas reservoirs,CO_(2) injection alleviates water locking and enhances gas-water flow,facilitating the recovery of trapped gas.The long-core CO_(2) flooding experiment results in a 14.11%increase in gas recovery efficiency.The effectiveness of CO_(2) -enhanced gas recovery (EGR) is primarily related to reservoir properties.Higher average permeability correlates with more effective CO_(2) -EGR.Although the rate and mode of injection have limited impacts on ultimate recovery efficiency,they influence CO_(2) breakthrough time.Specifically,a higher injection rate leads to earlier breakthrough,and the breakthrough under pulsed CO_(2) injection occurs later than that under continuous injection.展开更多
Gas chromatography-mass spectrometry(GC-MS)was used to analyze the pentacyclic triterpenoid distributions,specifically hopane and oleanane fingerprints,in 24 crude oil samples from the Niger Delta depobelts,with the a...Gas chromatography-mass spectrometry(GC-MS)was used to analyze the pentacyclic triterpenoid distributions,specifically hopane and oleanane fingerprints,in 24 crude oil samples from the Niger Delta depobelts,with the aim of defining the petroleum system,filling history,and the age of source rock producing these oils.The results indicate that the Niger Delta oils belong to a single fluvio-deltaic petroleum system,reflecting similar source organic facies and depositional environments.Geochemical parameters,including C29/C30hopane ratios,oleanane index,Ts/Tm,(Ts/(Ts+Tm)),moretane/C30hopane ratios,and C3222S/(22S+22R)ratios,suggest oxic conditions during source rock deposition and thermal maturity of the oils.The presence of terrigenous organic matter and complex filling history are also evident and influenced by multiple phases of sedimentation,and petroleum generation.A comparative plot of geologic time(Paleogene-Neogene age)and oleanane percentage composition show that the crude oils are constrained to the chronostratigraphic ages of their respective depobelts,demonstrating the potential of oleanane-derived parameters for relative dating of hydrocarbon sources,complementing traditional index fossil methods.展开更多
Volcanic reservoirs demonstrate strong heterogeneity and substantial variations in productivity due to the complexity of volcanic eruption and lithology.The main types of reservoir space are not clear,and the dominant...Volcanic reservoirs demonstrate strong heterogeneity and substantial variations in productivity due to the complexity of volcanic eruption and lithology.The main types of reservoir space are not clear,and the dominant lithofacies distribution,particularly the favorable areas for high-quality reservoirs,remains to be determined.In this paper,the Huoshiling Formation in the Dehui faulted depression,Songliao Basin is taken as an example to carry out the multi-scale joint characterization of its pore throat structure,establish a reservoir evaluation standard that considers both the gas content and seepage capacity,and perform reservoir evaluation and play fairway mapping under facies control.The results show that the storage space types of the gas-bearing reservoirs in the faulted depression can be ascribed into three categories and six subcategories according to the pore throat and pore characteristics.In terms of pore sizes,volcaniclastic lava rank the first,followed by volcaniclastic rocks,sedimentary volcaniclastic rocks and volcanic lava.The comprehensive evaluation parameter(Φ·K·Sg,whereΦis porosity,K permeability,and Sggas saturation)of high-quality reservoirs are all greater than 0.1.The volcanic reservoirs in the Stage-III strata are the highest in quality and largest in area of play fairways.The thermal debris flow sub-facies developed at Stage III are mainly seen along the western strike-slip fault zone in the Debei sub-sag and the southwest Nong'an tectonic belt,while those developed at Stage I are distributed along the central and eastern fault zones in the southeastern Baojia sub-sag.The favorable layer evaluation and favorable area delineation under facies control will be of certain reference significance for subsequent exploration and development of volcanic gas reservoirs.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
Machine learning techniques and a dataset of five wells from the Rawat oilfield in Sudan containing 93,925 samples per feature(seven well logs and one facies log) were used to classify four facies. Data preprocessing ...Machine learning techniques and a dataset of five wells from the Rawat oilfield in Sudan containing 93,925 samples per feature(seven well logs and one facies log) were used to classify four facies. Data preprocessing and preparation involve two processes: data cleaning and feature scaling. Several machine learning algorithms, including Linear Regression(LR), Decision Tree(DT), Support Vector Machine(SVM),Random Forest(RF), and Gradient Boosting(GB) for classification, were tested using different iterations and various combinations of features and parameters. The support vector radial kernel training model achieved an accuracy of 72.49% without grid search and 64.02% with grid search, while the blind-well test scores were 71.01% and 69.67%, respectively. The Decision Tree(DT) Hyperparameter Optimization model showed an accuracy of 64.15% for training and 67.45% for testing. In comparison, the Decision Tree coupled with grid search yielded better results, with a training score of 69.91% and a testing score of67.89%. The model's validation was carried out using the blind well validation approach, which achieved an accuracy of 69.81%. Three algorithms were used to generate the gradient-boosting model. During training, the Gradient Boosting classifier achieved an accuracy score of 71.57%, and during testing, it achieved 69.89%. The Grid Search model achieved a higher accuracy score of 72.14% during testing. The Extreme Gradient Boosting model had the lowest accuracy score, with only 66.13% for training and66.12% for testing. For validation, the Gradient Boosting(GB) classifier model achieved an accuracy score of 75.41% on the blind well test, while the Gradient Boosting with Grid Search achieved an accuracy score of 71.36%. The Enhanced Random Forest and Random Forest with Bagging algorithms were the most effective, with validation accuracies of 78.30% and 79.18%, respectively. However, the Random Forest and Random Forest with Grid Search models displayed significant variance between their training and testing scores, indicating the potential for overfitting. Random Forest(RF) and Gradient Boosting(GB) are highly effective for facies classification because they handle complex relationships and provide high predictive accuracy. The choice between the two depends on specific project requirements, including interpretability, computational resources, and data nature.展开更多
基金the North Dakota Industrial Commission (NDIC) for their financial supportprovided by the University of North Dakota Computational Research Center。
文摘Accurate estimation of mineralogy from geophysical well logs is crucial for characterizing geological formations,particularly in hydrocarbon exploration,CO_(2) sequestration,and geothermal energy development.Current techniques,such as multimineral petrophysical analysis,offer details into mineralogical distribution.However,it is inherently time-intensive and demands substantial geological expertise for accurate model evaluation.Furthermore,traditional machine learning techniques often struggle to predict mineralogy accurately and sometimes produce estimations that violate fundamental physical principles.To address this,we present a new approach using Physics-Integrated Neural Networks(PINNs),that combines data-driven learning with domain-specific physical constraints,embedding petrophysical relationships directly into the neural network architecture.This approach enforces that predictions adhere to physical laws.The methodology is applied to the Broom Creek Deep Saline aquifer,a CO_(2) sequestration site in the Williston Basin,to predict the volumes of key mineral constituents—quartz,dolomite,feldspar,anhydrite,illite—along with porosity.Compared to traditional artificial neural networks (ANN),the PINN approach demonstrates higher accuracy and better generalizability,significantly enhancing predictive performance on unseen well datasets.The average mean error across the three blind wells is 0.123 for ANN and 0.042 for PINN,highlighting the superior accuracy of the PINN approach.This method reduces uncertainties in reservoir characterization by improving the reliability of mineralogy and porosity predictions,providing a more robust tool for decision-making in various subsurface geoscience applications.
文摘The physical properties of hydrocarbon reservoirs are important factors affecting the percolation ability of the reservoirs.Tight-sand reservoirs exhibit complex pore throat connectivity due to the extensive development of micro-and nano-scale pore and throat systems.Characterizing the microscopic properties of these reservoirs using nondestructive,quantitative methods serves as an important means to determine the characteristics of microscopic pores and throats in tight-sand reservoirs and the mechanism behind the influence of these characteristics on reservoir porosity and permeability.In this study,a low-permeability sandstone sample and two tight sandstone samples collected from the Ordos Basin were nondestructively tested using high-resolution nano-CT technology to quantitively characterize their microscopic pore throat structures and model them three-dimensionally(in 3D)based on CT threshold differences and gray models.A thorough analysis and comparison reveal that the three samples exhibit a certain positive correlation between their porosity and permeability but the most important factor affecting both porosity and permeability is the microscopic pore throat structure.Although the number of pores in tight sandstones shows a minor impact on their porosity,large pores(more than 20μm)contribute predominantly to porosity,suggesting that the permeability of tight sandstones is controlled primarily by large pore throats.For these samples,higher permeability corresponds to larger average throat sizes.Therefore,throats with average radii greater than 2μm can significantly improve the permeability of tight sandstones.
文摘Key technologies that make productivity increase are revealed through analyzing the best practices and production data in major shale basins of North America.Trends of the key technologies and optimization designs for shale oil and gas development are summarized and analyzed based on drilling and completion operations and well data.These technologies mainly include:(1)Optimizing well design and hydraulic fracturing design,including reducing cluster spacing,increasing proppant and fracturing fluid volumes,optimizing horizontal well lateral length and fracture stage length.The most effective method is to reduce cluster spacing to an optimized length.The second most effective method is to optimally increase proppant volumes.(2)Placing horizontal wells in the sweet spots and drilling the wells parallel or close to the minimum horizontal stress direction.(3)Using cube development with optimized well spacing to maximize resource recovery and reduce well interferences.Plus,in-situ stress impacts on hydraulic fracture propagation and hydrocarbon production are addressed.Determination of formation breakdown pressure is studied by considering the impacts of in-situ stresses,drilling and perforation directions.Whether or not the hydraulic fracturing can generate orthogonal fracture networks is also discussed.The key technologies and optimization design parameters proposed in this paper can be applied to guide new well placement,drilling and completion designs,and hydraulic fracture operations to increase productivity.
基金funded by the Open Fund of Key Laboratory of Marine Geology and Environment,Chinese Academy of Sciences(Grant No.MGE2020KG10)the Open Fund of Key Laboratory of Submarine Geosciences,Ministry of Natural Resources(Grant No.KLSG 2208)+2 种基金the Natural Science Basic Research Program of Shaanxi(Grant No.2024JC-YBMS-227,2023-JC-QN-0287)the Postgraduate Innovation and Practice Ability Development Fund of Xi'an Shiyou University(No.YCS23113046)the National Natural Science Foundation of China(Grant No.41802128,42076219)。
文摘Tectonic activities significantly impact deep reservoir properties via sedimentary and diagenetic processes,and this is particularly true for lacustrine rift basins.The tectonic-sedimentary-diageneticreservoir system is crucial in deep reservoir exploration.This study examined the first member and upper submember of the second member of the Dongying Formation in the Bodong Low Uplift in the Bohai Bay Basin(East China),documenting the petrologic features and physical properties of reservoirs in different tectonic sub-units through integrated analysis of log and rock data,along with core observation.A mechanism for deep reservoir formation in lacustrine rift basins was developed to elucidate the sedimentary and diagenetic processes in complex tectonic settings.The results show that tectonic activities result in the occurrence of provenances in multiple directions and the existence of reservoirs at varying burial depths,as well as the significant diversity in sedimentary and diagenetic processes.The grain sizes of the sandstones,influenced by transport pathways rather than the topography of the sedimentary area,exhibit spatial complexity due to tectonic frameworks,which determine the initial pore content of reservoirs.However,the burial depth,influenced by subsequent tectonic subsidence,significantly impacts pore evolution during diagenesis.Based on the significant differences of reservoirs in slope zone,low uplift and depression zone,we establish different tectonic-diagenetic models in deep complex tectonic units of lacustrine rift basins.
文摘Gas-bearing shales have become a major source of future natural gas production worldwide.It has become increasingly urgent to develop a reliable prediction model and corresponding workflow for identifying shale gas sweet spots.The formation of gas-bearing shales is closely linked to relative sealevel changes,providing an important approach to predicting sweet spots in the Wufeng-Longmaxi shale in the southern Sichuan Basin,China.Three types of marine shale gas sweet spots are identified in the shale based on their formation stages combined with relative sea-level changes:early,middle,and late transgression types.This study develops a prediction model and workflow for identifying shale gas sweet spots by analyzing relative sea-level changes and facies sequences.Predicting shale gas sweet spots in an explored block using this model and workflow can provide a valuable guide for well design and hydraulic fracturing,significantly enhancing the efficiency of shale gas exploration and development.Notably,the new prediction model and workflow can be utilized for the rapid evaluation of the potential for shale gas development in new shale gas blocks or those with low exploratory maturity.
文摘CO_(2) flooding is a widely recognized method for enhanced oil recovery(EOR).This study aims to develop an accurate prediction method for determining the location and migration pathway of CO_(2) front,which plays an essential role in designing effective CO_(2) injection schemes and optimizing production strategies.Given the challenges of directly monitoring CO_(2) front movement in subsurface reservoirs,numerical well testing serves as an effective tool for indirectly inferring the location and migration characteristics of the CO_(2) front.This study established a numerical well-testing model based on a compositional framework to characterize interactions among multiple components during CO_(2) flooding.The methodology used in this model involves generating well-testing curves of CO_(2) flooding and then determining their flow stages based on CO_(2) distribution within reservoirs.Accordingly,a new well-testing analysis approach was proposed to determine the CO_(2) zone front and mixing zone front.This approach was applied to a pilot study of a practical oilfield,where it effectively predicted the positions of both fronts.The findings of this study reveal that the CO_(2) zone front and the mixing zone front correspond to the beginning of the first horizontal segment and the endpoint of the upward segment in the pressure derivative curve,respectively.This study introduces a cost-effective and time-efficient method for CO_(2) front monitoring,addressing the challenges of high costs and prolonged durations typically associated with CO_(2)-EOR operations.
基金funded by the National Science and Technology Major Project for the Exploration and Development of New Types of Oil and Gas(No.2024ZD14066)the National Natural Science Foundation of China(No.52274053)+1 种基金the Natural Science Foundation of Beijing Municipality(No.3173044)the Xinjiang Conglomerate Reservoir Laboratory Development Foundation Project(No.2020D04045)。
文摘Carbon dioxide enhanced oil recovery(CO_(2)-EOR)technology is used for oil production and CO_(2) storage in reservoirs.Methods are being constantly developed to optimize oil recovery and CO_(2) storage during the CO_(2) displacement process,especially for low-permeability reservoirs under varying geological conditions.In this study,long-core experiments and trans-scale numerical simulations are employed to examine the characteristics of oil production and CO_(2) storage.Optimal production parameters for the target reservoir are also proposed.The results indicate that maintaining the pressure at 1.04 to 1.10 times the minimum miscible pressure(MMP)and increasing the injection rate can enhance oil production in the early stage of reservoir development.In contrast,reducing the injection rate at the later stages prevents CO_(2) channeling,thus improving oil recovery and CO_(2) storage efficiency.A solution-doubling factor is introduced to modify the calculation method for CO_(2) storage,increasing its accuracy to approximately 90%.Before CO_(2) breakthrough,prioritizing oil production is recommended to maximize the economic benefits of this process.In the middle stage of CO_(2) displacement,decreasing the injection rate optimizes the coordination between oil displacement and CO_(2) storage.Further,in the late stage,reduced pressure and injection rates are required as the focus shifts to CO_(2) storage.
文摘This research pioneers the integration of geographic information systems(GIS)and 3D modeling within a virtual reality(VR)framework to assess the viability and planning of a 20 MW hybrid wind-solarphotovoltaic(PV)system connected to the local grid.The study focuses on Dakhla,Morocco,a region with vast untapped renewable energy potential.By leveraging GIS,we are innovatively analyzing geographical and environmental factors that influence optimal site selection and system design.The incorporation of VR technologies offers an unprecedented level of realism and immersion,allowing stakeholders to virtually experience the project's impact and design in a dynamic,interactive environment.This novel methodology includes extensive data collection,advanced modeling,and simulations,ensuring that the hybrid system is precisely tailored to the unique climatic and environmental conditions of Dakhla.Our analysis reveals that the region possesses a photovoltaic solar potential of approximately2400 k Wh/m^(2) per year,with an average annual wind power density of about 434 W/m^(2) at an 80-meter hub height.Productivity simulations indicate that the 20 MW hybrid system could generate approximately 60 GWh of energy per year and 1369 GWh over its 25-year lifespan.To validate these findings,we employed the System Advisor Model(SAM)software and the Global Solar Photovoltaic Atlas platform.This comprehensive and interdisciplinary approach not only provides a robust assessment of the system's feasibility but also offers valuable insights into its potential socio-economic and environmental impact.
文摘The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and fluid mobility due to the influences of the northeast and northwest dual provenance systems.This study performed multiple experimental analyses on nine samples from the area to determine the petrological and petrophysical properties,as well as the PTS characteristics of reservoirs in different provenance-controlled regions.On this basis,the pore-throat size distribution(PSD)obtained from high-pressure mercury injection(HPMI)was utilized to convert the NMR movable fluid T2spectrum,allowing for quantitative characterization of the full PSD and the occurrence characteristics of movable fluids.A systematic analysis was conducted on the primary controlling factors affecting fluid mobility in the reservoir.The results indicated that the lithology in the eastern and western regions is lithic arkose.The eastern sandstones,being farther from the provenance,exhibit higher contents of feldspar and lithic fragments,along with the development of more dissolution pores.The reservoir possesses good petrophysical properties,low displacement pressure,and high pore-throat connectivity and homogeneity,indicating strong fluid mobility.In contrast,the western sandstones,being nearer to the provenance,exhibit poor grain sorting,high contents of lithic fragments,strong compaction and cementation effects,resulting in poor petrophysical properties,and strong pore-throat heterogeneity,revealing weak fluid mobility.The range of full PSD in the eastern reservoir is wider than that in the western reservoir,with relatively well-developed macropores.The macropores are the primary space for occurrence of movable fluids,and controls the fluid mobility of the reservoir.The effective porosity of movable fluids(EPMF)quantitatively represents the pore space occupied by movable fluids within the reservoir and correlates well with porosity,permeability,and PTS parameters,making it a valuable parameter for evaluating fluid mobility.Under the multi-provenance system,the eastern and western reservoirs underwent different sedimentation and diagenesis processes,resulting in differential distribution of reservoir mineral components and pore types,which in turn affects the PTS heterogeneity and reservoir quality.The composition and content of reservoir minerals are intrinsic factors influencing fluid mobility,while the microscopic PTS is the primary factor controlling it.Low clay mineral content,welldeveloped macropores,and weak pore-throat heterogeneity all contribute to the storage and seepage of reservoir fluids.
基金funded by the National Natural Science Foundation of China(No.42141013)China Geological Survey(DD20221818,DD20242513).
文摘China has pledged to peak carbon dioxide(CO_(2))emissions by 2030 and achieve carbon neutrality by 2060.Carbon capture and storage(CCS)will play a key role in these efforts.Over the past several years,the China Geological Survey(CGS)has completed the Suitability Evaluation Map of CO_(2)Geological Storage in Main Sedimentary Basins in China and Adjacent Sea Regions in 2017.This map reflects the suitability of the first-and secondary-order tectonic units within sedimentary basins for cO_(2)geological storage for CCS planning.The Junggar Basin is recognized as an important region for future CCS projects.Results from a mesoscale evaluation using the volume method indicate that deep saline aquifers represent the most significant resources for CO_(2)storage,with potential ranging from 48×10^(9)to 164×10^(9)t(with a P50 value of 96×10^(9)t).The highest storage potential is identified in the central and northern parts of the basin,reaching up to 9.5×10^(6)t/km^(2)at the P50 probability level.In contrast,the hinterland,eastern,and western parts of the basin generally exhibit storage potential of below 1.0×10^(6)t/km^(2)at the same probability level.The CGs has also characterized historical CO_(2)plume migration in reservoirs at the storage site of the Shenhua CCS demonstration project and conducted numerical simulations of CO_(2)plume migration for periods of 10 and 20 years following the shutdown of the injection well.The CGS implemented a kiloton-scale pilot test on CO_(2)-enhanced water recovery(CO_(2)-EWR)in eastern Junggar,revealing that CO_(2)flooding can improve the pressure for fluid production,with the highest ratio of CO_(2)to produced fluids estimated at approximately 1.2.Besides,an observation field for natural CO_(2)leakage,covering about 930 m^(2),was built in Qinghai Province.In natural CO_(2)fields or at artificial CO_(2)injection research sites,cO_(2)leakage points are primarily related to the distribution of faults(especially fault crossing),which can serve as pathways for CO_(2)leakage.The observation field provides a natural analog to wellbore failure and offers an opportunity to further monitor CO_(2)geological storage sites.However,it has been inferred that borehole ZK10 at the observation field has become a leakage pathway due to the drilling activities,inadequate well-plugging,and abandonment procedures without considering CO_(2)corrosion.
文摘The Penobscot Field,located within the Scotian Basin offshore Nova Scotia,Canada,represents an underexplored hydrocarbon field with potential for future development.Previous studies have been confined to specific reservoir intervals without integrating multiple stratigraphic levels,and a comprehensive static reservoir characterization and volumetric assessment of the Penobscot Field has yet to be undertaken,constraining its full development evaluation.This study presents a comprehensive characte rization of the field by integrating geological,geophysical,and petrophysical datasets,leading to static hydrocarbon reserve estimation.The workflow involves seismic interpretation,structural modeling,petrophysical evaluation,and static volumetric calculations.Seismic analysis revealed a structu rally complex setting dominated by normal and inverted faults,with reservoir intervals primarily within the Missisauga Formation,which is subdivided into upper,middle,and lower units.Petro p hysical evaluation from well logs and core data identified key reservoir properties,including porosity ranging from 12 % to 28 %,permeability spanning from 1 to 1000 mD,and variable water saturations.Stochastic modeling of facies and petro p hysical attributes provided insights into lateral and ve rtical hete rogeneity.The Penobscot Field's original oil-in-place ranges from 41.6×10~6 m3 to 109.7×10~6 m3,with the Middle Missisauga sands presenting the highest reservoir potential.Fault seal analysis indicated predominantly sealing behavior in the shallow sections and semi-permeable conditions at greater depths,suggesting potential lateral migration pathways.The results underscore the field's hydrocarbon potential while emphasizing the significance of structural complexity,facies distribution,and petrophysical variability in reservoir quality,as well as its potential for future development or utilization of similar sand reservoirs for CO_(2) storage utilization.This work provides the first fully integrated static reservoir model of the Penobscot Field,offering critical insights for delineating the hydrocarbon reservoirs potential and future production strategies in the Scotian Basin.
基金funded by the National Key R&D Program of China(2024YFC2909400)the National Natural Science Foundation of China(42402180,42202195)the tackling applied science and technology projects of China National Petroleum Corporation(2023ZZ18)。
文摘Deep coal reservoirs(buried depth>2000 m)represent a significant yet underexploited resource for coalbed methane(CBM)production.In these reservoirs,CBM primarily exists in adsorbed and free phase,with the pore structure playing a critical role in gas storage and migration.The Jiaxian block in the northeastern Ordos Basin,has emerged as a key area for deep CBM exploration due to its promising resource potential.However,the pore structure characteristics of the No.8 coal seam in Jiaxian block and their implications for gas storage and production remain poorly understood.A comprehensive characterization of the No.8 coal seam's pore structure is conducted in the study using multiple methods including high-pressure mercury injection,N2/CO_(2)adsorption experiments,and integration of measured core gas content data and production history.The study results reveal that the pores can be mainly classified as vesicles and cellular pores,and the fractures are mainly static pressure fractures.Micropores(pore diameter<10 nm)dominate the pore system(accounting for more than 99%of the total specific surface area),providing important adsorption sites for gas storage.Although mesopores(pore diameter of 100-1000 nm)and macropores(pore diameter>1000 nm)account for a small proportion,they feature effective storage spaces and interconnectivity,resulting in a high proportion of free gas.Therefore,the reservoirs shows great development potential after stimulation(such as hydraulic fracturing).These findings emphasize the feasibility of large-scale and long-term development of CBM in the Jiaxian block in terms of reservoir space,gas content and production characteristics.This study serves to lay a scientific basis for its efficient exploitation.
基金funded by the Ministry of Science and Higher Education of the Russian Federation(Project No.FSNM-2023-0005).
文摘Many new and developed oilfields are confined to carbonate reservoirs with a complex void space structure.In this study,the behavior of carbonates as a function of decreased reservoir pressure was examined.The study was based on actual production data from wells rather than just on model data or results from computational experiments.Well-test data(170 well tests)and laboratory core samples(45 samples)results were used in the analysis.The problem of reservoir deformation has been compre-hensively addressed at the micro and macro levels.The effect of reservoir permeability throughout the entire reservoir volume on reservoir pressure was determined.With a decline in reservoir pressure,the permeability of fractures and pores in carbonates decreases.The deformation coefficients,which char-acterize the actual rate of decrease in permeability with decreasing reservoir pressure,were also calculated.The deformation coefficients and data from core studies using μ-CT and SEM were compared.Based on micro-CT data,the effective diameters of the voids were calculated to be 93μm,109μm,and 140μm for the Vinnikovskoe,Sofinskoe,and Sukharev fields,respectively.Based on μ-CT and SEM data,the predominant geometric shapes of the voids were assessed.The deformation coefficient of voids was found to depend on their size and geometric shape.The study's findings revealed deformation co-efficients of 0.172,0.205,and 0.748 for the Vinnikovskoe,Sofinskoe,and Sukharev fields,respectively.Maximum deformation coefficients are typical for large voids with a predominant slot-like shape.However,even with the predominance of primary spherical voids in carbonates,the permeability of voids decreases with decreasing reservoir pressure.
文摘An enhanced geothermal system(EGS)represents a promising approach to sustainable energy generation by harnessing subsurface heat from deep geological formations with low natural permeability.Sedimentary basins-such as the Williston Basin in North Dakota-are considered viable candidates for EGS development due to their broad geographic extent and moderate geothermal potential.Notably,depleted or non-productive oil wells within these basins offer a cost-effective opportunity for EGS implementation as they can be repurposed,thereby significantly reducing the need for new drilling.This study evaluates the feasibility of EGS deployment in McKenzie County,North Dakota.Core samples from five partially abandoned or dry oil wells associated with production from the Red River Formation were obtained from the Core Library of the North Dakota Geological Survey.These samples,spanning the entire thickness of the formation,were sectioned and polished at defined depth intervals for detailed analyses and precise measurements of key reservoir properties critical to geothermal assessment.Several parameters were analyzed to assess the geothermal viability of these wells,including formation temperature,temperature gradient,porosity,thermal conductivity,energy storage potential,and estimated power output via the Organic Rankine Cycle(ORC).The results demonstrate significant depth-dependent variations in thermal and petrophysical properties.Specifically,the depth range of 4000-4500 m is identified as a promising target for EGS stimulation since it is characterized by elevated temperatures,high thermal conductivity,favorable temperature gradients,and sufficient porosity-all essential properties for enhancing permeability through hydraulic fracturing.Furthermore,the calculated energy content and potential ORC power output at these depths indicate that effective geothermal energy extraction is technically feasible.This suggests a compelling opportunity to repurpose existing fossil energy infrastructure-such as abandoned oil wells-for renewable geothermal applications.Overall,the findings of this study underscore the potential of sedimentary formations for EGS development and contribute to advancing low-carbon,diversified energy solutions in alignment with national decarbonization goals.
文摘The Zagros Basin in southwestern Iran is a significant source of coal,with numerous coal mines operating in the region.Ensuring the stability of coal mines is crucial for safe and efficient mining operations.This study investigates the time-varying response of rocks and roof resistance in coal mines in the Zagros Mountains using a novel approach that combines numerical simulation,relaxation testing,and rock displacement studies.The results show that rocks exhibit significant time-dependent behavior,with changes in rock mechanical properties over time.A comprehensive viscoelastic-plastic model is devel-oped to accurately describe the time-varying strain-softening response of rocks and simulate laboratory tests.The model integrates the Burgers and strain-softening models,simulating stress relaxation curves and rock displacement over time.The study reveals that the rock mass displays significant nonlinear behavior,with changes in rock mechanical properties over time.The findings of this study highlight the importance of considering the time-varying response of rocks and roof resistance in coal mine stability analysis.The results provide valuable insights into the time-dependent behavior of rock mass in coal mines in Iran,which can inform mining practices and mitigate potential hazards.Results in this study can contribute to developing strategies for improving roof stability and reducing the likelihood of roof collapses.
基金funded by Basic Research Project of SINOPEC (P22202)。
文摘Experimental results from the Daniudi gas field enhance our understanding of mechanisms behind CO_(2) injection for enhanced recovery from tight-sand gas reservoirs.The results reveal that the diffusion coefficients of CO_(2) in tight reservoirs range from 10-8m2/s to 10-9m2/s,correlating negatively with pore pressure and positively with pore radius.In these reservoirs,CO_(2) manifests a significantly higher adsorption capability compared to CH4,suggesting a competitive adsorption advantage.Further,the amount of adsorbed gas correlates negatively with core permeability and positively with pore pressure.In the late-stage depletion-drive development of tight-sand gas reservoirs,CO_(2) injection alleviates water locking and enhances gas-water flow,facilitating the recovery of trapped gas.The long-core CO_(2) flooding experiment results in a 14.11%increase in gas recovery efficiency.The effectiveness of CO_(2) -enhanced gas recovery (EGR) is primarily related to reservoir properties.Higher average permeability correlates with more effective CO_(2) -EGR.Although the rate and mode of injection have limited impacts on ultimate recovery efficiency,they influence CO_(2) breakthrough time.Specifically,a higher injection rate leads to earlier breakthrough,and the breakthrough under pulsed CO_(2) injection occurs later than that under continuous injection.
文摘Gas chromatography-mass spectrometry(GC-MS)was used to analyze the pentacyclic triterpenoid distributions,specifically hopane and oleanane fingerprints,in 24 crude oil samples from the Niger Delta depobelts,with the aim of defining the petroleum system,filling history,and the age of source rock producing these oils.The results indicate that the Niger Delta oils belong to a single fluvio-deltaic petroleum system,reflecting similar source organic facies and depositional environments.Geochemical parameters,including C29/C30hopane ratios,oleanane index,Ts/Tm,(Ts/(Ts+Tm)),moretane/C30hopane ratios,and C3222S/(22S+22R)ratios,suggest oxic conditions during source rock deposition and thermal maturity of the oils.The presence of terrigenous organic matter and complex filling history are also evident and influenced by multiple phases of sedimentation,and petroleum generation.A comparative plot of geologic time(Paleogene-Neogene age)and oleanane percentage composition show that the crude oils are constrained to the chronostratigraphic ages of their respective depobelts,demonstrating the potential of oleanane-derived parameters for relative dating of hydrocarbon sources,complementing traditional index fossil methods.
基金funded by the National Natural Science Foundation of China(No.42172145)Natural Science Foundation of Heilongjiang Provincial(No.LH2022D014)。
文摘Volcanic reservoirs demonstrate strong heterogeneity and substantial variations in productivity due to the complexity of volcanic eruption and lithology.The main types of reservoir space are not clear,and the dominant lithofacies distribution,particularly the favorable areas for high-quality reservoirs,remains to be determined.In this paper,the Huoshiling Formation in the Dehui faulted depression,Songliao Basin is taken as an example to carry out the multi-scale joint characterization of its pore throat structure,establish a reservoir evaluation standard that considers both the gas content and seepage capacity,and perform reservoir evaluation and play fairway mapping under facies control.The results show that the storage space types of the gas-bearing reservoirs in the faulted depression can be ascribed into three categories and six subcategories according to the pore throat and pore characteristics.In terms of pore sizes,volcaniclastic lava rank the first,followed by volcaniclastic rocks,sedimentary volcaniclastic rocks and volcanic lava.The comprehensive evaluation parameter(Φ·K·Sg,whereΦis porosity,K permeability,and Sggas saturation)of high-quality reservoirs are all greater than 0.1.The volcanic reservoirs in the Stage-III strata are the highest in quality and largest in area of play fairways.The thermal debris flow sub-facies developed at Stage III are mainly seen along the western strike-slip fault zone in the Debei sub-sag and the southwest Nong'an tectonic belt,while those developed at Stage I are distributed along the central and eastern fault zones in the southeastern Baojia sub-sag.The favorable layer evaluation and favorable area delineation under facies control will be of certain reference significance for subsequent exploration and development of volcanic gas reservoirs.
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.
文摘Machine learning techniques and a dataset of five wells from the Rawat oilfield in Sudan containing 93,925 samples per feature(seven well logs and one facies log) were used to classify four facies. Data preprocessing and preparation involve two processes: data cleaning and feature scaling. Several machine learning algorithms, including Linear Regression(LR), Decision Tree(DT), Support Vector Machine(SVM),Random Forest(RF), and Gradient Boosting(GB) for classification, were tested using different iterations and various combinations of features and parameters. The support vector radial kernel training model achieved an accuracy of 72.49% without grid search and 64.02% with grid search, while the blind-well test scores were 71.01% and 69.67%, respectively. The Decision Tree(DT) Hyperparameter Optimization model showed an accuracy of 64.15% for training and 67.45% for testing. In comparison, the Decision Tree coupled with grid search yielded better results, with a training score of 69.91% and a testing score of67.89%. The model's validation was carried out using the blind well validation approach, which achieved an accuracy of 69.81%. Three algorithms were used to generate the gradient-boosting model. During training, the Gradient Boosting classifier achieved an accuracy score of 71.57%, and during testing, it achieved 69.89%. The Grid Search model achieved a higher accuracy score of 72.14% during testing. The Extreme Gradient Boosting model had the lowest accuracy score, with only 66.13% for training and66.12% for testing. For validation, the Gradient Boosting(GB) classifier model achieved an accuracy score of 75.41% on the blind well test, while the Gradient Boosting with Grid Search achieved an accuracy score of 71.36%. The Enhanced Random Forest and Random Forest with Bagging algorithms were the most effective, with validation accuracies of 78.30% and 79.18%, respectively. However, the Random Forest and Random Forest with Grid Search models displayed significant variance between their training and testing scores, indicating the potential for overfitting. Random Forest(RF) and Gradient Boosting(GB) are highly effective for facies classification because they handle complex relationships and provide high predictive accuracy. The choice between the two depends on specific project requirements, including interpretability, computational resources, and data nature.
