The Triassic Xujiahe Formation in the slope zone of the Sichuan foreland basin is a new field of continental tight gas exploration in recent years.The fourth member of the Xujiahe Formation(Xu4 Member),the major inter...The Triassic Xujiahe Formation in the slope zone of the Sichuan foreland basin is a new field of continental tight gas exploration in recent years.The fourth member of the Xujiahe Formation(Xu4 Member),the major interval in the Jianyang Block of the Tianfu gas field in the basin,is characterized by considerable buried depth,tight reservoirs,and strong heterogeneity.By using cast thin section,X-ray diffraction(XRD),scanning electron microscopy(SEM),fluid inclusion thermometry,and core analysis,the reservoir rock types,dominant diageneses,diagenetic history,and controls on high-graded reservoirs were investigated.It is found that the Xu4 Member in Jianyang mainly consists of lithic feldspar sandstones and feldspar lithic sandstones,followed by lithic quartz sandstones.High-energy hydrodynamic conditions in the microfacies of underwater distributary channels and mouth bars are beneficial to the preservation of primary pores and the occurrence of secondary pores,and there are no significant differences in petrophysical properties between these two microfacies.Compaction and calcareous cementation are the dominant controls on reservoir porosity decrease in the Xujiahe Formation;corrosion is the major contributor to porosity increase by generating secondary dissolved pores,e.g.intragranular dissolved pores and intergranular dissolved pores,as major reservoir space in the study area.Fracture zones around the faults inside the Xujiahe Formation(fourth‒order faults)are favorable for proximal tight gas accumulation,preservation,and production.The research findings have been successfully applied to explore the Xujiahe Formation in the slope zone of the Sichuan foreland basin.They can be referential for other similar tight sandstone gas accumulations.展开更多
In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members o...In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation(T1b2 and T1b3)in Ma-131 well area,which learned from the successful experience of hydraulic fracturing test sites in North America(HFTS-1).Twelve horizontal wells and a high-angle coring well MaJ02 were drilled.The orientation,connection,propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans,imaging logs,direct observation of cores from Well MaJ02,and combined with tracer monitoring data.Results indicate that:(1)Two types of fractures have developed by hydraulic fracturing,i.e.tensile fractures and shear fractures.Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress,and propagate less than 50 m from perforation clusters.Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures,and some of them are in conjugated pairs.Overall,tensile fractures alternate with shear fractures,with shear fractures dominated and activated after tensile ones.(2)Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production,and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed.(3)Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters,which is smaller in the mudstone than the conglomerate.Larger fracturing scale and smaller cluster spacing lead to a higher fracture density,which are important directions to improve the well productivity.展开更多
Tricellulin,a key tricellular tight junction(TJ)protein,is essential for maintaining the barrier integrity of acinar epithelia against macromolecular passage in salivary glands.This study aims to explore the role and ...Tricellulin,a key tricellular tight junction(TJ)protein,is essential for maintaining the barrier integrity of acinar epithelia against macromolecular passage in salivary glands.This study aims to explore the role and regulatory mechanism of tricellulin in the development of salivary gland hypofunction in Sjögren’s syndrome(SS).Employing a multifaceted approach involving patient biopsies,non-obese diabetic(NOD)mice as a SS model,salivary gland acinar cell-specific tricellulin conditional knockout(TricCKO)mice,and IFN-γ-stimulated salivary gland epithelial cells,we investigated the role of tricellulin in SS-related hyposalivation.Our data revealed diminished levels of tricellulin in salivary glands of SS patients.Similarly,NOD mice displayed a reduction in tricellulin expression from the onset of the disease,concomitant with hyposecretion and an increase in salivary albumin content.Consistent with these findings,TricCKO mice exhibited both hyposecretion and leakage of macromolecular tracers when compared to control animals.Mechanistically,the JAK/STAT1/miR-145 axis was identified as mediating the IFN-γ-induced downregulation of tricellulin.Treatment with AT1001,a TJ sealer,ameliorated epithelial barrier dysfunction,restored tricellulin expression,and consequently alleviated hyposalivation in NOD mice.Importantly,treatment with miR-145 antagomir to specifically recover the expression of tricellulin in NOD mice significantly alleviated hyposalivation and macromolecular leakage.Collectively,we identified that tricellulin deficiency in salivary glands contributed to hyposalivation in SS.Our findings highlight tricellulin as a potential therapeutic target for hyposecretion,particularly in the context of reinforcing epithelial barrier function through preventing leakage of macromolecules in salivary glands.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
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
Supercritical CO_(2)(SC-CO_(2))fracturing stands out a promising waterless stimulation technique in the development of unconventional resources.While numerous studies have delved into the inducedfracture mechanism of ...Supercritical CO_(2)(SC-CO_(2))fracturing stands out a promising waterless stimulation technique in the development of unconventional resources.While numerous studies have delved into the inducedfracture mechanism of SC-CO_(2),the small scale of rock samples and synthetic materials used in many studies have limited a comprehensive understanding of fracture propagation in unconventional formations.In this study,cubic tight sandstone samples with dimensions of 300 mm were employed to conduct SC-CO_(2)fractu ring experiments under true-triaxial stre ss conditions.The spatial morphology and quantitative attributes of fracture induced by water and SC-CO_(2)fracturing were compared,while the impact of in-situ stress on fracture propagation was also investigated.The results indicate that the SCCO_(2)fracturing takes approximately ten times longer than water fracturing.Furthermore,under identical stress condition,the breakdown pressure(BP)for SC-CO_(2)fracturing is nearly 25%lower than that for water fracturing.A quantitative analysis of fracture morphology reveals that water fracturing typically produces relatively simple fracture pattern,with the primary fracture distribution predominantly controlled by bedding planes.In contrast,SC-CO_(2)fracturing results in a more complex fracture morphology.As the differential of horizontal principal stress increases,the BP for SC-CO_(2)fractured rock exhibits a downward trend,and the induced fracture morphology becomes more simplified.Moreover,the presence of abnormal in-situ stress leads to a further increase in the BP for SC-CO_(2)fracturing,simultaneously enhancing the development of a more conductive fracture network.These findings provide critical insights into the efficiency and behavior of SC-CO_(2)fracturing in comparison to traditional water-based fracturing,offering valuable implication for its potential applications in unconventional reservoirs.展开更多
Understanding the storage mechanisms in CO_(2)flooding is crucial,as many carbon capture,utilization,and storage(CCUS)projects are related to enhanced oil recovery(EOR).CO_(2)storage in reservoirs across large timesca...Understanding the storage mechanisms in CO_(2)flooding is crucial,as many carbon capture,utilization,and storage(CCUS)projects are related to enhanced oil recovery(EOR).CO_(2)storage in reservoirs across large timescales undergoes the two storage stages of oil displacement and well shut-in,which cover mul-tiple replacement processes of injection-production synchronization,injection only with no production,and injection-production stoppage.Because the controlling mechanism of CO_(2)storage in different stages is unknown,the evolution of CO_(2)storage mechanisms over large timescales is not understood.A math-ematical model for the evaluation of CO_(2)storage,including stratigraphic,residual,solubility,and mineral trapping in low-permeability tight sandstone reservoirs,was established using experimental and theoret-ical analyses.Based on a detailed geological model of the Huaziping Oilfield,calibrated with reservoir permeability and fracture characteristic parameters obtained from well test results,a dynamic simulation of CO_(2)storage for the entire reservoir life cycle under two scenarios of continuous injection and water-gas alternation were considered.The results show that CO_(2)storage exhibits the significant stage charac-teristics of complete storage,dynamic storage,and stable storage.The CO_(2)storage capacity and storage rate under the continuous gas injection scenario(scenario 1)were 6.34×10^(4)t and 61%,while those under the water-gas alternation scenario(scenario 2)were 4.62×10^(4)t and 46%.The proportions of stor-age capacity under scenarios 1 and 2 for structural or stratigraphic,residual,solubility,and mineral trap-ping were 33.36%,33.96%,32.43%,and 0.25%;and 15.09%,38.65%,45.77%,and 0.49%,respectively.The evolution of the CO_(2)storage mechanism showed an overall trend:stratigraphic and residual trapping first increased and then decreased,whereas solubility trapping gradually decreased,and mineral trapping continuously increased.Based on these results,an evolution diagram of the CO_(2)storage mechanism of low-permeability tight sandstone reservoirs across large timescales was established.展开更多
Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of he...Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of heterogeneity in oil-bearing reservoirs, a high-pressure mercury injection experiment combined with fractal theory was conducted to analyze the micro pore throat structure characteristics of the tight sandstone of Chang 7 Member reservoirs in the Ordos Basin. The factors controlling the variations in oil content among tight sandstone samples were identified based on mineral composition characteristics. The results indicate that the pore throat radius distribution is mainly unimodal an bimodal. In oil-bearing samples, the pore throat distributions align well with the corresponding permeability contribution curves, while in oil-free samples, there is a clear deviation from these curves. Mesopore throats exert the greatest influence on seepage capacity. Differences in fractal characteristics are primarily reflected in D1 values, with oil-free samples exhibiting D1 values close to 3, indicating an extremely nonuniform pore throat structure at this scale. The content of quartz, plagioclase, and chlorite is significantly higher in oil-bearing samples than in oil-free samples, whereas calcite content is lower in oil-bearing samples. There is a positive correlation between the contents of quartz, plagioclase, and chlorite with D1;their increased presence contributes to a more favorable pore throat structure.Conversely, the calcite contents show an inverse relationship with D1. Cementation increases the complexity of pore throat structures, while multiple diagenetic processes simultaneously control these characteristics, leading to variations in oil content.展开更多
The pore structures of the Majiagou Formation in the Ordos Basin are complex,featuring micro-and nano-scale intra-crystalline and inter-crystalline pores that significantly impact hydrocarbon storage and flow.Precisel...The pore structures of the Majiagou Formation in the Ordos Basin are complex,featuring micro-and nano-scale intra-crystalline and inter-crystalline pores that significantly impact hydrocarbon storage and flow.Precisely characterizing the rock internal structures is crucial for reservoir exploration and development.However,it is difficult to accurately characterize the pore structure of rock using traditional imaging methods to meet the simulation requirements.In this context,this study focuses on high-resolution 3D digital core reconstruction using the SliceGAN model.Specifically,the Modular Automated Processing System(MAPS)image and Quanti-tative Evaluation of Minerals by Scanning Electron Microscopy(QEMSCAN)image were combined to divide MAPS into three categories:pore,dolomite,and calcite.Then,through the SliceGAN algorithm,the 3D digital core was reconstructed.To evaluate the reconstruction,the auto-correlation function,two-point probability function,porosity,mineral content,and specific surface area were employed.The results show that the SliceGAN can effectively capture the micro-features in the core,and the internal structure of the generated core was consistent with that of the original core.This study provided a new sight for reconstructing cores with complex pore structures and strong heterogeneity and innovatively supports tight carbonate reservoir characterization and evaluation.展开更多
In the context of complex tectonic evolution,due to the control of tectonic compression stress and faults on tectonic fractures,the formation and development of tectonic fractures in the T_3x~2 tight reservoirs presen...In the context of complex tectonic evolution,due to the control of tectonic compression stress and faults on tectonic fractures,the formation and development of tectonic fractures in the T_3x~2 tight reservoirs present significant variations across different tectonic segments in the Western Sichuan Foreland Basin.We clarified the control of differential tectonic evolution on the formation and development of tectonic fractures in different tectonic segments through field-based observations,core samples,image logging,as well as fluid inclusion petrography and temperature determinations of fracture-filling materials,combined with 2D balanced cross-section restoration.The study area primarily manifests two types of tectonic fractures in the tight reservoirs:orogen-related fractures(regional fractures)and fault-related fractures.The orientations of these fractures are predominantly E-W,nearly N-S,NE,and NW.Specifically,the northern segment area only shows the development of regional fractures,while the southern and middle segments exhibit the development of both regional and tectonic fractures.There are three phases of tectonic fractures in different tectonic segments,and their formation times are relatively consistent.The Mesozoic tectonic events had a significant impact on the northern and central segments,with the amount of tectonic shortening and the rate of stratigraphic shortening gradually decreasing from the northeast to the southwest.The compressional stress resulting from tectonic compression also decreases from the northeast to the southwest.As a result,the development of first-phase and second-phase tectonic shear fractures is more pronounced in the northern and middle segments compared to the southern segment.Under the significant control of faults,the development of N-S-and NE-oriented fault-related fractures is more pronounced in the southern segment,while the development of NE-oriented fault-related fractures is relatively higher in the middle segment.Overall,there is an increased density of fractures and an increasing trend in fracture scale from the northern to the middle and then to the southern segment.展开更多
The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oi...The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oil and gas exploitation.The complex fluid flow in such reservoirs is analyzed using a combination of theoretical modeling and numerical simulation.This study develops a comprehensive mathematical model that integrates the impact of creep on the seepage process,with consideration of factors including stress,strain,and time-dependent deformation.The model is validated through a series of numerical experiments,which demonstrate the significant influence of creep on the seepage behavior.The results indicate that the rock mechanical parameters and creep constitutive model were determined through triaxial compression tests and uniaxial creep tests.A creep-seepage coupling control equation for shale was established based on the Burgers creep model.The absolute value of the volumetric strain of shale increases rapidly in the initial creep stage,and the increase in vertical stress accelerates the rock’s creep deformation.During the deceleration creep stage,the volumetric strain of the reservoir increases rapidly,leading to a significant decrease in permeability.In the stable creep stage,the pores and fractures in the rock are further compressed,causing a gradual reduction in permeability,which eventually stabilizes.展开更多
High saturation pressure reservoirs experience rapid pressure decline during exploitation,leading to significant changes in crude oil phase behavior and a continuous increase in viscosity after degassing,which adverse...High saturation pressure reservoirs experience rapid pressure decline during exploitation,leading to significant changes in crude oil phase behavior and a continuous increase in viscosity after degassing,which adversely affects oil recovery.This challenge is particularly acute in tight sandstone reservoirs.To optimize the development strategy for such reservoirs,a series of experiments were conducted using core samples from a high saturation tight sandstone reservoir in the JS oilfield.Gas-dissolved crude oil was prepared by mixing wellhead oil and gas samples,enabling the identification of the critical point where viscosity changes as pressure decreases.Oil-water relative permeability experiments under varying viscosities revealed crude oilmobility trends with declining production pressure.Additionally,physical and numerical simulations of water huff-n-puff processeswere performed,while nuclear magnetic resonance methods explored the effects of soaking time on oil-water imbibition.Key findings include the following optimal parameters for water huff-n-puff:(1)initiating the process when formation pressure is 75%of its original level,(2)a soaking time of 48 h,(3)an injection volume of 0.6 pore volumes per cycle,and(4)a 5 MPa pressure reduction per production stage.Numerical simulations further recommend initiating water injection after one year of depletion,with an optimal cumulative injection volume of 18,000 cubic meters,a soaking time of 10 days,and a producing pressure difference of 5 MPa.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
This study sheds light on how pore structure characteristics and varying dynamic pressure conditions influence the permeability of tight sandstone reservoirs,with a particular focus on the Paleozoic reservoirs in the ...This study sheds light on how pore structure characteristics and varying dynamic pressure conditions influence the permeability of tight sandstone reservoirs,with a particular focus on the Paleozoic reservoirs in the Qingshimao Gas Field.Using CT scans of natural core samples,a three-dimensional digital core was constructed.The maximum ball method was applied to extract a related pore network model,and the pore structure characteristics of the core samples,such as pore radius,throat radius,pore volume,and coordination number,were quantitatively evaluated.The analysis revealed a normally distributed pore radius,suggesting a high degree of reservoir homogeneity and favorable conditions for a connected pore system.However,it was found that the majority of throat radii measured less than 1μm,which severely restricted fluid flow and diminished permeability.Over 50%of the pores measured under 100μm^(3),further constraining fluid movement.Additionally,30%-50%of the pore network was composed of isolated and blind-end pores,which significantly impaired formation connectivity and reduced permeability.Based on this,the lattice Boltzmann method(LBM)was used for pore-scale flow simulation to investigate the influence mechanism of pore structure characteristics and dynamic-static parameters such as displacement pressure difference on the permeability performance of the considered tight sandstone reservoirs for various pressure gradients(0.1,1,and 10 MPa).The simulations revealed a strong relationship between pressure differential and both the number of streamlines and flow path tortuosity.When the pressure differential increased to 1 MPa,30 streamlines were observed,with a tortuosity factor of 1.5,indicating the opening of additional seepage channels and the creation of increasingly winding flow paths.展开更多
A precise diagnosis of the complex post-fracturing characteristics and parameter variations in tight gas reservoirs is essential for optimizing fracturing technology,enhancing treatment effectiveness,and assessing pos...A precise diagnosis of the complex post-fracturing characteristics and parameter variations in tight gas reservoirs is essential for optimizing fracturing technology,enhancing treatment effectiveness,and assessing post-fracturing production capacity.Tight gas reservoirs face challenges due to the interaction between natural fractures and induced fractures.To address these issues,a theoretical model for diagnosing fractures under varying leak-off mechanisms has been developed,incorporating the closure behavior of natural fractures.This model,grounded in material balance theory,also accounts for shut-in pressure.The study derived and plotted typical G-function charts,which capture fracture behavior during closure.By superimposing the G-function in the closure phase of natural fractures with pressure derivative curves,the study explored how fracture parameters—including leak-off coefficient,fracture area,closure pressure,and closure time—impact these diagnostic charts.Findings show that variations in natural fracture flexibility,fracture area,and controlling factors influence the superimposed G-function pressure derivative curve,resulting in distinctive“concave”or“convex”patterns.Field data from Well Y in a specific tight gas reservoir were used to validate the model,confirming both its reliability and practicality.展开更多
Research based on oil accumulation models is essential for exploring the hydrocarbon accumulation theory further.Studies on tight oil accumulation models focused on fan delta depositional systems,and in particular,sys...Research based on oil accumulation models is essential for exploring the hydrocarbon accumulation theory further.Studies on tight oil accumulation models focused on fan delta depositional systems,and in particular,systems involving source-reservoir separated type are scarce.To explore the accumulation model of tight oil in conglomerate,this study focused on the Permian-Triassic tight conglomerate oil in Mahu sag,Junggar Basin,using well drilling,well logging,seismic profiling,oil testing,and laboratory data,and analyzed the formation conditions,formation types,and distribution patterns of conglomerate reservoirs.The results show that,the conglomerate reservoirs are predominantly lithologic reservoirs and partly fault-lithologic reservoirs;there is no water evident at the edge or bottom around the reservoirs.The tight conglomerate layer in the delta plain subfacies of each fan exhibits high clay content and intense diagenesis,and the argillaceous rocks in the pro-fan delta subfacies and shallow lacustrine facies form the sealing and floor conditions.The sandy conglomerate of fan delta front subfacies is the main reservoir body.Additionally,strikeslip faulting in the Indosinian-Himalayan period formed an efficient faulting system for trans-stratal migration with Hercynian-Indosinian inverse faulting.Oil migration is driven by the overpressure caused by hydrocarbon generation from alkali lacustrine source rocks.The distribution of reservoirs is primarily controlled by the large fan bodies,namely the Zhongguai,Baijiantan,Karamay,Huangyangquan,Xiazijie,Xiayan,and Dabasong fans.Each fan body forms a group of reservoirs or oilfields,resulting in a widely distributed pattern,according to which reservoir and sealing constitute one whole body—i.e.,patterns of“one sand and one reservoir,one fan and one field.”This results in a quasi-continuous accumulation model,which includes strong oil charging,efficient faulting transportation,trans-stratal migration,and lithologic trapped accumulation.The proposed model is an important supplement to the existing model of quasi-continuous oil and gas accumulation.Overall,this study enriches unconventional oil and gas accumulation theories.展开更多
The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion...The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion system analysis and in situ U-Pb dating,the sequence of tight sandstone reservoir densification and oil charging was determined.Through petrological observations,fluid inclusion analysis and physical property analysis,it is concluded that compaction and cementation are the primary causes of reservoir densification.When the content of calcite cement is less than or equal to 7%,compaction dominates densification;otherwise,cementation becomes more significant.However,determining the exact timing of compaction densification proved challenging.Microscopic observations revealed that oil charging likely occurred either before or during the densification of the reservoir.According to in situ U-Pb dating and the porosity evolution curve,cementation densification occurred between 167.0±20.0 Ma and 151.8 Ma.Temperature measurements of the aqueous inclusions indicate that oil charging occurred between 125.0 and 96.0 Ma,suggesting that densification preceded oil charging.This study provides valuable insights for the future exploration of tight oil reservoirs in the Ordos Basin.展开更多
Improvement of the detection ability of quantum entanglement is one of the essential tasks in quantum computing and quantum information.Finite tight frames play a fundamental role in a wide variety of areas and,genera...Improvement of the detection ability of quantum entanglement is one of the essential tasks in quantum computing and quantum information.Finite tight frames play a fundamental role in a wide variety of areas and,generally,each application requires a specific class of frames and is closely related to quantum measurement.It is worth noting that a maximal set of complex equiangular vectors is closely related to a symmetric informationally complete measurement.Hence,our goal in this work is to propose a series of separability criteria assigned to a finite tight frame and some well-known inequalities in different quantum systems,respectively.In addition,some tighter criteria to detect entanglement for many-body quantum states are presented in arbitrary dimensions.Finally,the effectiveness of the proposed entanglement detection criteria is illustrated through some detailed examples.展开更多
Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in ...Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in the southern Junggar Basin to comprehensively analyze the fracture characteristics and differential distribution and,ultimately,addressed the controlling mechanisms of tectonism and diagenesis on fracture effectiveness.Results revealed that the intensity of tectonic activities determines the complexity of tectonic fracture systems to create various fracture orientations when they have been stronger.The intense tectonic deformation would impact the stratum occurrence,which results in a wide range of fracture dip angles.Moreover,as the intensity of tectonic activities and deformations weakens,the scale and degree of tectonic fractures would decrease continuously.The control of tectonism on fracture effectiveness is reflected in the notable variations in the filling of multiple group fractures developed during different tectonic activity periods.Fractures formed in the early stages are more likely to be filled with minerals,causing their effectiveness to deteriorate significantly.Additionally,the strong cementation in the diagenetic evolution can cause more fractures to be filled with minerals and become barriers to fluid flow,which is detrimental to fracture effectiveness.However,dissolution is beneficial in improving their effectiveness by increasing fracture aperture and their connectivity to the pores.These insights can refine the development pattern of natural fractures and contribute to revealing the evolutionary mechanisms of fracture effectiveness in deep tight sandstone reservoirs of foreland thrust belts.展开更多
Tight oil reservoirs face significant challenges,including rapid production decline,low recovery rates,and a lack of effective energy replenishment methods.In this study,a novel development model is proposed,based on ...Tight oil reservoirs face significant challenges,including rapid production decline,low recovery rates,and a lack of effective energy replenishment methods.In this study,a novel development model is proposed,based on inter-fracture injection following volumetric fracturing and relying on a high-temperature and high-pressure large-scale physical simulation system.Additionally,the CMG(Computer Modelling Group Ltd.,Calgary City,Canada)software is also used to elucidate the impact of various single factors on the production of horizontal wells while filtering out the interference of others.The effects of fracture spacing,fracture half-length,and the injection-production ratio are studied.Results indicate that under rejection pressures of 6.89,3.45,and 1.88 MPa,the times to establish stable flow are 50,193,and 395 min,respectively.Higher injection pressures lead to an increased oil recovery efficiency,with the highest observed efficiency at 16.93%.This indicates that,compared with conventional medium and high permeability reservoirs,tight oil reservoirs exhibit similar pore throats and larger capillary forces when oil and water flow in both phases.Higher pressures reduce capillary forces,displacing more oil droplets,thus enhancing oil recovery efficiency.Moreover,under inter-fracture displacement conditions,the pressure gradient at both the injection and production ends remain consistent,with minimal pressure loss near the wellbore.This feature ensures that the crude oil in the middle of the reservoir also possesses displacement energy,thereby enhancing overall crude oil displacement efficiency.展开更多
基金supported by the China National Petroleum Corporation Science and Technology Project(Study on genesis mechanism and distribution law of high quality reservoir of the fourth Member of Xujiahe Formation in middle and west Sichuan area,20230301-23)。
文摘The Triassic Xujiahe Formation in the slope zone of the Sichuan foreland basin is a new field of continental tight gas exploration in recent years.The fourth member of the Xujiahe Formation(Xu4 Member),the major interval in the Jianyang Block of the Tianfu gas field in the basin,is characterized by considerable buried depth,tight reservoirs,and strong heterogeneity.By using cast thin section,X-ray diffraction(XRD),scanning electron microscopy(SEM),fluid inclusion thermometry,and core analysis,the reservoir rock types,dominant diageneses,diagenetic history,and controls on high-graded reservoirs were investigated.It is found that the Xu4 Member in Jianyang mainly consists of lithic feldspar sandstones and feldspar lithic sandstones,followed by lithic quartz sandstones.High-energy hydrodynamic conditions in the microfacies of underwater distributary channels and mouth bars are beneficial to the preservation of primary pores and the occurrence of secondary pores,and there are no significant differences in petrophysical properties between these two microfacies.Compaction and calcareous cementation are the dominant controls on reservoir porosity decrease in the Xujiahe Formation;corrosion is the major contributor to porosity increase by generating secondary dissolved pores,e.g.intragranular dissolved pores and intergranular dissolved pores,as major reservoir space in the study area.Fracture zones around the faults inside the Xujiahe Formation(fourth‒order faults)are favorable for proximal tight gas accumulation,preservation,and production.The research findings have been successfully applied to explore the Xujiahe Formation in the slope zone of the Sichuan foreland basin.They can be referential for other similar tight sandstone gas accumulations.
基金Supported by the National Natural Science Foundation of China(52274051)CNPC-China University of Petroleum(Beijing)Strategic Cooperative Project(ZLZX2020-01).
文摘In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation(T1b2 and T1b3)in Ma-131 well area,which learned from the successful experience of hydraulic fracturing test sites in North America(HFTS-1).Twelve horizontal wells and a high-angle coring well MaJ02 were drilled.The orientation,connection,propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans,imaging logs,direct observation of cores from Well MaJ02,and combined with tracer monitoring data.Results indicate that:(1)Two types of fractures have developed by hydraulic fracturing,i.e.tensile fractures and shear fractures.Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress,and propagate less than 50 m from perforation clusters.Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures,and some of them are in conjugated pairs.Overall,tensile fractures alternate with shear fractures,with shear fractures dominated and activated after tensile ones.(2)Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production,and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed.(3)Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters,which is smaller in the mudstone than the conglomerate.Larger fracturing scale and smaller cluster spacing lead to a higher fracture density,which are important directions to improve the well productivity.
基金supported by the National Natural Science Foundation of China(grants 31972908,81991500,81991502,and 32030010)Beijing Natural Science Foundation(grant 7202082).
文摘Tricellulin,a key tricellular tight junction(TJ)protein,is essential for maintaining the barrier integrity of acinar epithelia against macromolecular passage in salivary glands.This study aims to explore the role and regulatory mechanism of tricellulin in the development of salivary gland hypofunction in Sjögren’s syndrome(SS).Employing a multifaceted approach involving patient biopsies,non-obese diabetic(NOD)mice as a SS model,salivary gland acinar cell-specific tricellulin conditional knockout(TricCKO)mice,and IFN-γ-stimulated salivary gland epithelial cells,we investigated the role of tricellulin in SS-related hyposalivation.Our data revealed diminished levels of tricellulin in salivary glands of SS patients.Similarly,NOD mice displayed a reduction in tricellulin expression from the onset of the disease,concomitant with hyposecretion and an increase in salivary albumin content.Consistent with these findings,TricCKO mice exhibited both hyposecretion and leakage of macromolecular tracers when compared to control animals.Mechanistically,the JAK/STAT1/miR-145 axis was identified as mediating the IFN-γ-induced downregulation of tricellulin.Treatment with AT1001,a TJ sealer,ameliorated epithelial barrier dysfunction,restored tricellulin expression,and consequently alleviated hyposalivation in NOD mice.Importantly,treatment with miR-145 antagomir to specifically recover the expression of tricellulin in NOD mice significantly alleviated hyposalivation and macromolecular leakage.Collectively,we identified that tricellulin deficiency in salivary glands contributed to hyposalivation in SS.Our findings highlight tricellulin as a potential therapeutic target for hyposecretion,particularly in the context of reinforcing epithelial barrier function through preventing leakage of macromolecules in salivary glands.
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 Scientific Foundation of China(Nos.52304008,52404038,52474043)the China Postdoctoral Science Foundation(No.2023MD734223)+1 种基金the Key Laboratory of Well Stability and Fluid&Rock Mechanics in Oil and Gas Reservoir of Shaanxi Province(No.23JS047)the Youth Talent Lifting Program of Xi'an Science and Technology Association(No.959202413078)。
文摘Supercritical CO_(2)(SC-CO_(2))fracturing stands out a promising waterless stimulation technique in the development of unconventional resources.While numerous studies have delved into the inducedfracture mechanism of SC-CO_(2),the small scale of rock samples and synthetic materials used in many studies have limited a comprehensive understanding of fracture propagation in unconventional formations.In this study,cubic tight sandstone samples with dimensions of 300 mm were employed to conduct SC-CO_(2)fractu ring experiments under true-triaxial stre ss conditions.The spatial morphology and quantitative attributes of fracture induced by water and SC-CO_(2)fracturing were compared,while the impact of in-situ stress on fracture propagation was also investigated.The results indicate that the SCCO_(2)fracturing takes approximately ten times longer than water fracturing.Furthermore,under identical stress condition,the breakdown pressure(BP)for SC-CO_(2)fracturing is nearly 25%lower than that for water fracturing.A quantitative analysis of fracture morphology reveals that water fracturing typically produces relatively simple fracture pattern,with the primary fracture distribution predominantly controlled by bedding planes.In contrast,SC-CO_(2)fracturing results in a more complex fracture morphology.As the differential of horizontal principal stress increases,the BP for SC-CO_(2)fractured rock exhibits a downward trend,and the induced fracture morphology becomes more simplified.Moreover,the presence of abnormal in-situ stress leads to a further increase in the BP for SC-CO_(2)fracturing,simultaneously enhancing the development of a more conductive fracture network.These findings provide critical insights into the efficiency and behavior of SC-CO_(2)fracturing in comparison to traditional water-based fracturing,offering valuable implication for its potential applications in unconventional reservoirs.
基金supported by the National Key Research and Development Program of China(2022YFE0206700).
文摘Understanding the storage mechanisms in CO_(2)flooding is crucial,as many carbon capture,utilization,and storage(CCUS)projects are related to enhanced oil recovery(EOR).CO_(2)storage in reservoirs across large timescales undergoes the two storage stages of oil displacement and well shut-in,which cover mul-tiple replacement processes of injection-production synchronization,injection only with no production,and injection-production stoppage.Because the controlling mechanism of CO_(2)storage in different stages is unknown,the evolution of CO_(2)storage mechanisms over large timescales is not understood.A math-ematical model for the evaluation of CO_(2)storage,including stratigraphic,residual,solubility,and mineral trapping in low-permeability tight sandstone reservoirs,was established using experimental and theoret-ical analyses.Based on a detailed geological model of the Huaziping Oilfield,calibrated with reservoir permeability and fracture characteristic parameters obtained from well test results,a dynamic simulation of CO_(2)storage for the entire reservoir life cycle under two scenarios of continuous injection and water-gas alternation were considered.The results show that CO_(2)storage exhibits the significant stage charac-teristics of complete storage,dynamic storage,and stable storage.The CO_(2)storage capacity and storage rate under the continuous gas injection scenario(scenario 1)were 6.34×10^(4)t and 61%,while those under the water-gas alternation scenario(scenario 2)were 4.62×10^(4)t and 46%.The proportions of stor-age capacity under scenarios 1 and 2 for structural or stratigraphic,residual,solubility,and mineral trap-ping were 33.36%,33.96%,32.43%,and 0.25%;and 15.09%,38.65%,45.77%,and 0.49%,respectively.The evolution of the CO_(2)storage mechanism showed an overall trend:stratigraphic and residual trapping first increased and then decreased,whereas solubility trapping gradually decreased,and mineral trapping continuously increased.Based on these results,an evolution diagram of the CO_(2)storage mechanism of low-permeability tight sandstone reservoirs across large timescales was established.
基金supported by the National Natural Science Foundation of China (Grant No. 42002139)the Basic Prospective Project of SINOPEC (Grant No. P23240-3)。
文摘Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of heterogeneity in oil-bearing reservoirs, a high-pressure mercury injection experiment combined with fractal theory was conducted to analyze the micro pore throat structure characteristics of the tight sandstone of Chang 7 Member reservoirs in the Ordos Basin. The factors controlling the variations in oil content among tight sandstone samples were identified based on mineral composition characteristics. The results indicate that the pore throat radius distribution is mainly unimodal an bimodal. In oil-bearing samples, the pore throat distributions align well with the corresponding permeability contribution curves, while in oil-free samples, there is a clear deviation from these curves. Mesopore throats exert the greatest influence on seepage capacity. Differences in fractal characteristics are primarily reflected in D1 values, with oil-free samples exhibiting D1 values close to 3, indicating an extremely nonuniform pore throat structure at this scale. The content of quartz, plagioclase, and chlorite is significantly higher in oil-bearing samples than in oil-free samples, whereas calcite content is lower in oil-bearing samples. There is a positive correlation between the contents of quartz, plagioclase, and chlorite with D1;their increased presence contributes to a more favorable pore throat structure.Conversely, the calcite contents show an inverse relationship with D1. Cementation increases the complexity of pore throat structures, while multiple diagenetic processes simultaneously control these characteristics, leading to variations in oil content.
基金financially supported by the open fund of Key Lab-oratory of Exploration Technologies for Oil and Gas Resources(Yangtze University),Ministry of Education,NO PI2023-03the open foundation of the National Engineering Laboratory for Exploration and Develop-ment of Low-Permeability Oil&Gas Fields and the National Natural Science Foundation of China(No.42474159).
文摘The pore structures of the Majiagou Formation in the Ordos Basin are complex,featuring micro-and nano-scale intra-crystalline and inter-crystalline pores that significantly impact hydrocarbon storage and flow.Precisely characterizing the rock internal structures is crucial for reservoir exploration and development.However,it is difficult to accurately characterize the pore structure of rock using traditional imaging methods to meet the simulation requirements.In this context,this study focuses on high-resolution 3D digital core reconstruction using the SliceGAN model.Specifically,the Modular Automated Processing System(MAPS)image and Quanti-tative Evaluation of Minerals by Scanning Electron Microscopy(QEMSCAN)image were combined to divide MAPS into three categories:pore,dolomite,and calcite.Then,through the SliceGAN algorithm,the 3D digital core was reconstructed.To evaluate the reconstruction,the auto-correlation function,two-point probability function,porosity,mineral content,and specific surface area were employed.The results show that the SliceGAN can effectively capture the micro-features in the core,and the internal structure of the generated core was consistent with that of the original core.This study provided a new sight for reconstructing cores with complex pore structures and strong heterogeneity and innovatively supports tight carbonate reservoir characterization and evaluation.
基金financially supported by the National Natural Science Foundation of China(No.42402171)the China Postdoctoral Science Foundation(No.2023MD744255)+6 种基金the Natural Science Basic Research Program of Shaanxi(No.2024JC-YBQN-0353)the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.23JK0600)the Shaanxi Postdoctoral Science Foundation(No.2023BSHEDZZ324)the project of Theory of Hydrocarbon Enrichment under Multi-Spheric Interactions of the Earth(No.THEMSIE04010107)the Key Research and Development Program of Shaanxi(No.2021KW-10)the Innovation Capability Support Program of Shaanxi(No.2022PT-08)the SINOPEC CCUS Fund Project(No.33550000-22ZC0613-0326)。
文摘In the context of complex tectonic evolution,due to the control of tectonic compression stress and faults on tectonic fractures,the formation and development of tectonic fractures in the T_3x~2 tight reservoirs present significant variations across different tectonic segments in the Western Sichuan Foreland Basin.We clarified the control of differential tectonic evolution on the formation and development of tectonic fractures in different tectonic segments through field-based observations,core samples,image logging,as well as fluid inclusion petrography and temperature determinations of fracture-filling materials,combined with 2D balanced cross-section restoration.The study area primarily manifests two types of tectonic fractures in the tight reservoirs:orogen-related fractures(regional fractures)and fault-related fractures.The orientations of these fractures are predominantly E-W,nearly N-S,NE,and NW.Specifically,the northern segment area only shows the development of regional fractures,while the southern and middle segments exhibit the development of both regional and tectonic fractures.There are three phases of tectonic fractures in different tectonic segments,and their formation times are relatively consistent.The Mesozoic tectonic events had a significant impact on the northern and central segments,with the amount of tectonic shortening and the rate of stratigraphic shortening gradually decreasing from the northeast to the southwest.The compressional stress resulting from tectonic compression also decreases from the northeast to the southwest.As a result,the development of first-phase and second-phase tectonic shear fractures is more pronounced in the northern and middle segments compared to the southern segment.Under the significant control of faults,the development of N-S-and NE-oriented fault-related fractures is more pronounced in the southern segment,while the development of NE-oriented fault-related fractures is relatively higher in the middle segment.Overall,there is an increased density of fractures and an increasing trend in fracture scale from the northern to the middle and then to the southern segment.
基金supported by the National Natural Science Foundation of China(Grant Nos.42472195 and 42272153)the Research Fund of PetroChina Tarim Oilfield Company(Grant No.671023060003)Technology Projects of China National Petroleum Corporation(Grant No.2023ZZ16YJ02).
文摘The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oil and gas exploitation.The complex fluid flow in such reservoirs is analyzed using a combination of theoretical modeling and numerical simulation.This study develops a comprehensive mathematical model that integrates the impact of creep on the seepage process,with consideration of factors including stress,strain,and time-dependent deformation.The model is validated through a series of numerical experiments,which demonstrate the significant influence of creep on the seepage behavior.The results indicate that the rock mechanical parameters and creep constitutive model were determined through triaxial compression tests and uniaxial creep tests.A creep-seepage coupling control equation for shale was established based on the Burgers creep model.The absolute value of the volumetric strain of shale increases rapidly in the initial creep stage,and the increase in vertical stress accelerates the rock’s creep deformation.During the deceleration creep stage,the volumetric strain of the reservoir increases rapidly,leading to a significant decrease in permeability.In the stable creep stage,the pores and fractures in the rock are further compressed,causing a gradual reduction in permeability,which eventually stabilizes.
基金supported by the Innovation Fund of China National Petroleum Corporation(2020D-5007-0209).
文摘High saturation pressure reservoirs experience rapid pressure decline during exploitation,leading to significant changes in crude oil phase behavior and a continuous increase in viscosity after degassing,which adversely affects oil recovery.This challenge is particularly acute in tight sandstone reservoirs.To optimize the development strategy for such reservoirs,a series of experiments were conducted using core samples from a high saturation tight sandstone reservoir in the JS oilfield.Gas-dissolved crude oil was prepared by mixing wellhead oil and gas samples,enabling the identification of the critical point where viscosity changes as pressure decreases.Oil-water relative permeability experiments under varying viscosities revealed crude oilmobility trends with declining production pressure.Additionally,physical and numerical simulations of water huff-n-puff processeswere performed,while nuclear magnetic resonance methods explored the effects of soaking time on oil-water imbibition.Key findings include the following optimal parameters for water huff-n-puff:(1)initiating the process when formation pressure is 75%of its original level,(2)a soaking time of 48 h,(3)an injection volume of 0.6 pore volumes per cycle,and(4)a 5 MPa pressure reduction per production stage.Numerical simulations further recommend initiating water injection after one year of depletion,with an optimal cumulative injection volume of 18,000 cubic meters,a soaking time of 10 days,and a producing pressure difference of 5 MPa.
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This study sheds light on how pore structure characteristics and varying dynamic pressure conditions influence the permeability of tight sandstone reservoirs,with a particular focus on the Paleozoic reservoirs in the Qingshimao Gas Field.Using CT scans of natural core samples,a three-dimensional digital core was constructed.The maximum ball method was applied to extract a related pore network model,and the pore structure characteristics of the core samples,such as pore radius,throat radius,pore volume,and coordination number,were quantitatively evaluated.The analysis revealed a normally distributed pore radius,suggesting a high degree of reservoir homogeneity and favorable conditions for a connected pore system.However,it was found that the majority of throat radii measured less than 1μm,which severely restricted fluid flow and diminished permeability.Over 50%of the pores measured under 100μm^(3),further constraining fluid movement.Additionally,30%-50%of the pore network was composed of isolated and blind-end pores,which significantly impaired formation connectivity and reduced permeability.Based on this,the lattice Boltzmann method(LBM)was used for pore-scale flow simulation to investigate the influence mechanism of pore structure characteristics and dynamic-static parameters such as displacement pressure difference on the permeability performance of the considered tight sandstone reservoirs for various pressure gradients(0.1,1,and 10 MPa).The simulations revealed a strong relationship between pressure differential and both the number of streamlines and flow path tortuosity.When the pressure differential increased to 1 MPa,30 streamlines were observed,with a tortuosity factor of 1.5,indicating the opening of additional seepage channels and the creation of increasingly winding flow paths.
文摘A precise diagnosis of the complex post-fracturing characteristics and parameter variations in tight gas reservoirs is essential for optimizing fracturing technology,enhancing treatment effectiveness,and assessing post-fracturing production capacity.Tight gas reservoirs face challenges due to the interaction between natural fractures and induced fractures.To address these issues,a theoretical model for diagnosing fractures under varying leak-off mechanisms has been developed,incorporating the closure behavior of natural fractures.This model,grounded in material balance theory,also accounts for shut-in pressure.The study derived and plotted typical G-function charts,which capture fracture behavior during closure.By superimposing the G-function in the closure phase of natural fractures with pressure derivative curves,the study explored how fracture parameters—including leak-off coefficient,fracture area,closure pressure,and closure time—impact these diagnostic charts.Findings show that variations in natural fracture flexibility,fracture area,and controlling factors influence the superimposed G-function pressure derivative curve,resulting in distinctive“concave”or“convex”patterns.Field data from Well Y in a specific tight gas reservoir were used to validate the model,confirming both its reliability and practicality.
基金the National Science and Technology Major Project of China for their support。
文摘Research based on oil accumulation models is essential for exploring the hydrocarbon accumulation theory further.Studies on tight oil accumulation models focused on fan delta depositional systems,and in particular,systems involving source-reservoir separated type are scarce.To explore the accumulation model of tight oil in conglomerate,this study focused on the Permian-Triassic tight conglomerate oil in Mahu sag,Junggar Basin,using well drilling,well logging,seismic profiling,oil testing,and laboratory data,and analyzed the formation conditions,formation types,and distribution patterns of conglomerate reservoirs.The results show that,the conglomerate reservoirs are predominantly lithologic reservoirs and partly fault-lithologic reservoirs;there is no water evident at the edge or bottom around the reservoirs.The tight conglomerate layer in the delta plain subfacies of each fan exhibits high clay content and intense diagenesis,and the argillaceous rocks in the pro-fan delta subfacies and shallow lacustrine facies form the sealing and floor conditions.The sandy conglomerate of fan delta front subfacies is the main reservoir body.Additionally,strikeslip faulting in the Indosinian-Himalayan period formed an efficient faulting system for trans-stratal migration with Hercynian-Indosinian inverse faulting.Oil migration is driven by the overpressure caused by hydrocarbon generation from alkali lacustrine source rocks.The distribution of reservoirs is primarily controlled by the large fan bodies,namely the Zhongguai,Baijiantan,Karamay,Huangyangquan,Xiazijie,Xiayan,and Dabasong fans.Each fan body forms a group of reservoirs or oilfields,resulting in a widely distributed pattern,according to which reservoir and sealing constitute one whole body—i.e.,patterns of“one sand and one reservoir,one fan and one field.”This results in a quasi-continuous accumulation model,which includes strong oil charging,efficient faulting transportation,trans-stratal migration,and lithologic trapped accumulation.The proposed model is an important supplement to the existing model of quasi-continuous oil and gas accumulation.Overall,this study enriches unconventional oil and gas accumulation theories.
基金supported by the project of the Exploration Department of the Huabei Oilfield Company of Sinopec(No.34550008-20-ZC0609-0031).
文摘The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion system analysis and in situ U-Pb dating,the sequence of tight sandstone reservoir densification and oil charging was determined.Through petrological observations,fluid inclusion analysis and physical property analysis,it is concluded that compaction and cementation are the primary causes of reservoir densification.When the content of calcite cement is less than or equal to 7%,compaction dominates densification;otherwise,cementation becomes more significant.However,determining the exact timing of compaction densification proved challenging.Microscopic observations revealed that oil charging likely occurred either before or during the densification of the reservoir.According to in situ U-Pb dating and the porosity evolution curve,cementation densification occurred between 167.0±20.0 Ma and 151.8 Ma.Temperature measurements of the aqueous inclusions indicate that oil charging occurred between 125.0 and 96.0 Ma,suggesting that densification preceded oil charging.This study provides valuable insights for the future exploration of tight oil reservoirs in the Ordos Basin.
基金supported by the Natural Science Foundation of Sichuan Province(Grant No.25QNJJ4066)。
文摘Improvement of the detection ability of quantum entanglement is one of the essential tasks in quantum computing and quantum information.Finite tight frames play a fundamental role in a wide variety of areas and,generally,each application requires a specific class of frames and is closely related to quantum measurement.It is worth noting that a maximal set of complex equiangular vectors is closely related to a symmetric informationally complete measurement.Hence,our goal in this work is to propose a series of separability criteria assigned to a finite tight frame and some well-known inequalities in different quantum systems,respectively.In addition,some tighter criteria to detect entanglement for many-body quantum states are presented in arbitrary dimensions.Finally,the effectiveness of the proposed entanglement detection criteria is illustrated through some detailed examples.
基金supported by the CNPC Innovation Found(No.2023DQ02-0103)National Major Science and Technology Projects of China(No.2016ZX05003-001).
文摘Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in the southern Junggar Basin to comprehensively analyze the fracture characteristics and differential distribution and,ultimately,addressed the controlling mechanisms of tectonism and diagenesis on fracture effectiveness.Results revealed that the intensity of tectonic activities determines the complexity of tectonic fracture systems to create various fracture orientations when they have been stronger.The intense tectonic deformation would impact the stratum occurrence,which results in a wide range of fracture dip angles.Moreover,as the intensity of tectonic activities and deformations weakens,the scale and degree of tectonic fractures would decrease continuously.The control of tectonism on fracture effectiveness is reflected in the notable variations in the filling of multiple group fractures developed during different tectonic activity periods.Fractures formed in the early stages are more likely to be filled with minerals,causing their effectiveness to deteriorate significantly.Additionally,the strong cementation in the diagenetic evolution can cause more fractures to be filled with minerals and become barriers to fluid flow,which is detrimental to fracture effectiveness.However,dissolution is beneficial in improving their effectiveness by increasing fracture aperture and their connectivity to the pores.These insights can refine the development pattern of natural fractures and contribute to revealing the evolutionary mechanisms of fracture effectiveness in deep tight sandstone reservoirs of foreland thrust belts.
基金supported by the Study on the Seepage Law of Typical Low-Grade Oil Reservoirs,New Methods for Enhancing Oil Recovery(2021DJ1102)the National Science and Technology Major Special Support Program(Grant No.2017ZX05064)the CNPC Innovation Foundation(Grant No.2022DQ02-0604).
文摘Tight oil reservoirs face significant challenges,including rapid production decline,low recovery rates,and a lack of effective energy replenishment methods.In this study,a novel development model is proposed,based on inter-fracture injection following volumetric fracturing and relying on a high-temperature and high-pressure large-scale physical simulation system.Additionally,the CMG(Computer Modelling Group Ltd.,Calgary City,Canada)software is also used to elucidate the impact of various single factors on the production of horizontal wells while filtering out the interference of others.The effects of fracture spacing,fracture half-length,and the injection-production ratio are studied.Results indicate that under rejection pressures of 6.89,3.45,and 1.88 MPa,the times to establish stable flow are 50,193,and 395 min,respectively.Higher injection pressures lead to an increased oil recovery efficiency,with the highest observed efficiency at 16.93%.This indicates that,compared with conventional medium and high permeability reservoirs,tight oil reservoirs exhibit similar pore throats and larger capillary forces when oil and water flow in both phases.Higher pressures reduce capillary forces,displacing more oil droplets,thus enhancing oil recovery efficiency.Moreover,under inter-fracture displacement conditions,the pressure gradient at both the injection and production ends remain consistent,with minimal pressure loss near the wellbore.This feature ensures that the crude oil in the middle of the reservoir also possesses displacement energy,thereby enhancing overall crude oil displacement efficiency.
