In response to issues such as high water cuts and simultaneous gas-water production during the development of the J58 well block in the Ordos Basin,this study evaluates the influence of various reservoir factors on movable fluids based on pore-throat size classification in tight sandstone reservoirs.This helps to clarify the gas distribution pattern from a microscopic perspective.Taking 10 typical tight sandstone cores from the Shihezi Formation as examples,casting thin section observation,scanning electron microscopy(SEM),X-ray diffraction(XRD),high-pressure mercury intrusion(HPMI),and nuclear magnetic resonance(NMR)experiments were conducted.Using multifractal theory and NMR parameter-based pore-throat distribution transformation methods,the impact of reservoir parameters on the distribution of movable fluids within pore throats of different sizes was assessed.The results show that based on the shape and parameters of mercury intrusion curves,the pore structure can be divided into three types.Type Ⅰ shows a bimodal distribution of pore-throat sizes,with good physical properties and connec-tivity;Type Ⅱ shows an unimodal distribution dominated by medium-sized pores,with good sorting,but due to limited pore-throat size,their physical properties are inferior to Type Ⅰ;Type Ⅲ have a pore-throat size distribution dominated by nanopores as the main peak and mesopores as the secondary peak,with the strongest heterogeneity in physical properties.According to the turning points in pore-throat size and fractal characteristic curves,the pore throats can be classified into mesopores(0.1～1 μm),micropores(0.01～0.1 μm),and nanopores(0.001～0.01 μm).Movable fluids are mainly found within mesopores and micropores,where the mesopores content plays a decisive role in the volume of movable fluids,while micropores,when in relatively high proportion,also have certain gas storage potential.Nanopores,however,have little impact on movable fluid distribution.The content of brittle minerals mainly affects the amount of movable fluid in mesopores,whereas clay mineral content has a negative impact on movable fluid content across all pore-throat sizes.The porosity contributed by different pore-throat sizes is positively correlated with movable fluid content;however,this correlation decreases as pore-throat size decreases due to the influence of reservoir connectivity.Permeability controls the distribution of movable fluids within pore throats of different sizes.Among pore-throat structure parameters,a higher fractal dimension negatively affects the distribution of movable fluids both overall and within pore-throats of different sizes.Owing to the limitations imposed by differing contributions of pore-throat sizes to reservoir properties,the maximum mercury saturation parameter can only be used to characterize the distribution of movable fluids within mesopores.

Shale pores serve as the primary reservoir space for shale gas,whose structural characteristics directly determine the gas occurrence state,enrichment degree,and flow mechanisms.However,the complex structure and strong heterogeneity of organic pores in shale gas reservoirs significantly constrain precise reservoir evaluation and dynamic development.To clarify the three-dimensional structural characteristics of organic pores in the Lower Paleozoic shale reservoirs in South China,this study focuses on two organic-rich shale successions in the northern Guizhou:The Lower Cambrian Niutitang Formation and the Lower Silurian Longmaxi Formation shales,which exhibit significantly different thermal maturities.An integrated approach was employed,combining organic matter extraction,low-temperature nitrogen adsorption,and focused ion beam-scanning electron microscopy(FIB-SEM)three-dimensional reconstruction techniques to systematically characterize the microstructure of organic pores in these two shale successions.Based on nitrogen adsorption and FIB data,the Frenkel-Halsey-Hill(FHH)and box-counting models were respectively applied to evaluate the complexity of organic matter pore structures across different scales.The results show that the moderately mature Longmaxi Formation shale(equivalent vitrinite reflectance Ro=2.1%～2.8%)contains well-developed organic pores,predominantly exhibiting bubble-like and sponge-like cluster morphologies with pore sizes(r)mainly ranging from 200 nm to 450 nm,along with high specific surface area(133.9～159.5 m2/g)and substantial pore volume.In contrast,the overmature Niutitang Formation shale(Ro=3.0%～3.8%)contains smaller organic pores(r=10～140?nm)with irregular or slit-shaped geometries,showing lower specific surface area(30.9～31.4 m2/g)and reduced pore volume.Three-dimensional pore network modeling further reveals distinct connectivity patterns between these two shale successions.In the Longmaxi Formation shale,organic pores are primarily isolated with poor connectivity,and large pores(r>140 nm)contribute approximately 70%of the total pore volume.The Niutitang Formation shale,however,shows enhanced connectivity among large pores(r>150 nm)through thermal-induced microfractures formed during organic matter condensation,while small pores(r<150 nm)remain largely isolated yet account for 64%of the total pore volume.Fractal dimension analysis highlights additional structural differences.The Niutitang Formation shale exhibits higher fractal dimensions for large organic matter pores(D2=2.37～2.78),indicating greater structural complexity,whereas the organic pores of the Longmaxi Formation shale display relatively regular geometries with lower fractal dimensions.These variations are mainly controlled by differences in thermal maturity.Our study provides systematic understanding of three-dimensional pore structure evolution in shales with different thermal maturities,and offers theoretical foundations for shale gas reservoir evaluation and development strategies in northern Guizhou.

Mobility is an important parameter of tight sandstone in the process of oil and gas development,prediction,and evaluation.The complex diagenesis process and the lack of knowledge about the control mechanism of the evolution process on mobility restrict the understanding of the hydrocarbon accumulation mechanism and"sweet spot"optimization of tight sandstone.In this study,the tight sandstone of the Fuyu oil layer of the Quantou Formation in the northern Songliao Basin was taken as the research object.Utilizing a combination of high-pressure mercury injection,nuclear magnetic resonance,scanning electron microscopy,and thin section observation,the mechanism of diagenesis on the mobility of tight sandstone in the diagenetic evolution process was explored.The results show that compaction mainly occurs in the early diagenesis stage.The pore types are mainly primary pores and residual intergranular pores.Macropores and mesopores are mainly developed.Macropores are the main occurrence space of movable fluid,and the saturation of movable fluid is high.In the middle diagenesis stage A,compaction and dissolution mainly occur,and a certain degree of cementation occurs at the same time.The pore types are mainly residual intergranular pores and dissolution pores.The pore structure is gradually complicated and the connectivity is reduced.The proportion of mesopores gradually increases,and the saturation of movable fluid continues to decrease.In the B stage of the middle diagenetic stage,cementation mainly occurred.The precipitation of many cements occupied the effective reservoir space and throats such as residual intergranular pores and dissolution pores.The macropores almost disappeared,and the mesopores became the main occurrence space of the fluid,and the mobility was poor.The control of diagenesis on reservoir pore structure in different diagenesis stages determines the mobility of tight sandstone reservoirs.Finally,the mobility evolution model of the tight sandstone reservoirs under the constraint of diagenetic evolution is established.The potential relationship between diagenetic evolution,pore structure,and free fluid occurrence is clarified.All these can help a better understanding of the spatial distribution law and mobility difference of sweet spots in the tight sandstone reservoirs,and also provide a conceptual basis for further optimization of development means and technical schemes.

The lower Cambrian organic-rich shales are widely distributed in the middle-upper Yangtze platform,which are also the main target layers for shale gas exploration and extraction.Revealing the enrichment mechanisms of organic matter in these shales is of great significance for understanding the relationship between ocean bio-environmental systems and Earth resources.Through systematical geochemical analyses,this study investigated the lower Cambrian Niutitang Formation slope facies shales at the western Xuefeng Uplift,to elucidate the paleoenvironmental characteristics and their main controlling factors.The results show that the Niutitang Formation shales generally have high TOC contents,with higher TOC contents in the lower part than those in the upper part.Sedimentological geochemistry analyses indicate that the Niutitang Formation formed under high pa-leo-productivity and anoxic-anaerobic even sulfurized conditions.The formation generally has a lower degree of reduction in the late period of sedimentation than at earlier times,and was deposited in a moderately hydrologically restricted setting,with weak terrestrial input and hydrothermal activities.The enrichment of organic matter in the Niutitang Formation slope facies shales was mainly controlled by the redox conditions,however upwelling currents also contributed to the primary input of organic matter.During the early deposition stage of the Niutitang Formation,the nutrients brought by upwelling currents promoted primary paleo-productivity,resulting in the booming of algal organisms and subsequent bacterial sulfate reduction(BSR)and anoxic even sulfurized environments.During the late deposition stage of the Niutitang Formation,a drop in sea level led to a weaker degree of reduction and lower contents of TOC.Our results are of great significance to the enrichment mechanisms of marine organic-rich shales in petroliferous basins.

China is rich in shale oil resources.By the end of 2022,the predicted reserves of continental shale oil in China have reached 3 billion tonnes,but only recoverable shale oil has economic value under such reserves.The shale oil reservoirs of the Lucaogou For-mation in the Jimusar Sag can be divided into three types:interlayer type,lamina type and block type according to mineral composition and source-reservoir ratio.However,due to the large difference in pore structure characteristics and fluid occurrence state of the three types of reservoirs,the productivity difference is high using the same fracturing method.In order to clarify the pore structure character-istics of the Lucaogou interlayer and laminated reservoirs in the Jimusar sag and the difference of fluid mobility under their constraints,this paper studies the pore structure characteristics by means of XRD,casting thin sections,scanning electron microscopy and nitrogen adsorption.Nuclear magnetic resonance centrifugation technology was used to quantitatively evaluate the mobility of shale oil in laminated and laminated reservoir samples.The T1-T2 spectrum method was used to clarify the occurrence state of shale oil in different reservoir types.Finally,the main controlling factors of fluid mobility in shale oil reservoirs were analyzed by combining characteristic pore structure parameters.The results show that the carbonate content of laminated reservoirs is high,and the reservoir space is domi-nated by carbonate intergranular pores,clay mineral interlayer fractures and organic matter pores.The fluid component is dominated by kerogen,and the free oil component content is extremely low.The average value of movable fluid saturation is only 7.97%.The felsic content of the interlayer type is higher,the reservoir space is mainly composed of intercrystalline pores and dissolved pores in feldspar grains,the fluid composition is mainly movable oil,followed by bound oil and kerogen,and there is no movable water.The average saturation of movable fluid is 29.3%.The pore throat radius in the characteristic pore structure parameters is the main factor controlling the movable fluid saturation of shale oil reservoirs.The two are exponentially correlated,and the correlation coefficient can reach 0.95.Through the study,the main reservoir space types of the intergranular pores and intra-granular pores in the Lucaogou Formation and the laminar shale oil reservoirs in the Jimsal Depression are determined.The mobile fluid saturation decreases gradually from unimodal interlayer reservoirs to bimodal laminated reservoirs,but increases exponentially with the increase of the maximum pore throat radius.The results show that the maximum pore throat radius has a great influence on the mobile fluid saturation of shale oil reservoir.

The Yangchungou area is a key replacement area for shale gas exploration in eastern Sichuan in China.Its main control fault,the Yangchungou fault,is an important structure affecting shale gas accumulation in the area,but there are few previous studies,resulting in a low degree of overall research.In order to clarify the structural deformation characteristics of the Yangchungou fault and its geological significance,based on the latest interpretation of three-dimensional seismic data,the geometric characteristics of the Yangchungou fault are described.And we analyze its formation mechanism through fault properties and activity period.Based on this,the relationship between the Yangchungou and Zunyi faults and its influence on shale gas accumulation are discussed.The results show that:(1)The Yangchungou fault is mainly characterized by a planar thrust structure from east to west.The surface outcrop data show characteristics of sinistral compression and torsion.In addition,the Yangchungou fault is characterized by multiple superimposed and nearly parallel thrust slip fault zones along the Silurian and Cambrian,which control the fault development anticline of the middle and shallow deformation layers.(2)The Yangchungou fault is not a part of the Zunyi fault.The structural deformation characteristics of the Yangchungou and Zunyi faults are very different.They show completely different structural styles in seismic profiles.Therefore,the Yangchungou fault and the Zunyi fault are not two parts of the same fault.(3)The Yangchungou fault formed a small fault in a nearly north-south direction during the early Xuefeng orogeny,which caused the Zunyi fault to undergo left lateral reverse washing and sliding.The current form of the Yangchungou fault was formed in the late stage by the reverse compression torsion of the arc-shaped folded wing from east to west.Therefore,the Yangchungou fault has undergone uneven contraction from the Late Jurassic to the Late Cretaceous and reverse sliding from east to west in the Late Cretaceous.(4)The Yangchungou fault has formed the Yangchungou anticline and a complex fracture network.The Yangchungou anticline reduces the depth of shale burial,slows down the evolution of shale maturity,and the complex fracture network increases the storage space,but does not seriously damage the preservation conditions.Both are conducive to the migration and accumulation of shale gas into reservoirs.The development of high and steep strata and compressional and torsional faults can have a destructive effect on shale gas reservoirs.The results of this study can help for better understanding the basin-mountain coupling process and shale gas exploration.

The Early Cretaceous Yingcheng Formation shale gas in the Lishu Fault Depression of the Songliao Basin presents immense prospects for exploration and development.Concurrently,the division of high-frequency sequences within shale intervals has gradually become a research focus.However,traditional sequence stratigraphy faces challenges in the precise delineation of sequences within the shale series,while the understanding of organic matter enrichment patterns within the shale series remains unclear,hindering the exploration and development of shale oil and gas.The utilization of cyclostratigraphy meth-ods allows for the subdivision of high-frequency sequences within the shale series,and further,it provides a beneficial means to explore the enrichment patterns of organic matter in shale based on Milankovitch cycles,aiding in the prediction of"sweet spots"within the layers.Through astronomical cycle analysis of natural gamma-ray data from the research area in the Yingcheng Formation,the following conclusions have been drawn:(1)Well SN65 effectively preserves the signals of Milankovitch cycles within the Yingcheng Formation.Long and short eccentricities serve as reference curves for the fourth and fifth-order sequences,respectively,delineating 14 fourth-order sequences and 51 fifth-order sequences,thus establishing a high-precision isochronous stratigraphic framework for the study area.(2)The organic matter enrichment of the shale within the Yingcheng Formation on the northern slope of the Lishu Fault Depression is controlled by astronomical cycles,exhibiting an antiphase relationship.During periods of high long eccentricity,the climate was warm and humid,corresponding to low Total Organic Carbon(TOC)values;conversely,during periods of low long eccentricity,the climate was cold and dry,corresponding to high TOC values.(3)Two shale sedimentation models have been established:warm-humid and cold-dry.Through the introduction of the concept of the metalimnetic oxygen minimum(MOM),it has been demonstrated that cold-dry environments are conducive to the enrichment of organic matter in shale.(4)The data were divided into 4 organic-rich shale intervals and 3 organic matter-bearing shale intervals based on the half-amplitude points of the long eccentricity cycle curve.High-quality shale intervals develop at the tops and bottoms of various sequences rather than at the maximum flooding surface.Shallow water environments are conducive to the development of organic-rich shale.These research findings not only provide theoretical support for predicting"sweet spots"of shale gas within the Yingcheng Formation in the Lishu Fault Depression of the Songliao Basin but also serve as a reference for the organic matter enrichment patterns in other lacustrine basins,holding significant implications for the evaluation of shale oil and gas exploration selection.

The development of micro-nano-scale pores and microfractures in the Fuyu tight sandstone reservoirs of the Cretaceous Quantou Formation in the northern part of the Songliao Basin,as well as the complex structure of the pores and fractures,leads to the unclear sequence of tight oil and gas filling in different types of reservoir spaces during the formation period,which increases the difficulty of exploration and development of tight oil and gas.In this paper,a quantitative study is conducted on the filling characteristics of tight oil under different filling pressures in tight sandstone reservoirs,and a microscopic evaluation method of tight oil filling patterns based on pore-microfracture combinations is proposed by combining large field-of-view splicing swept electron microscopy and mineral surface scanning technology.The study shows that the Fuyu tight sandstone reservoirs of the Quantou Formation in the area can be classified into three main types of pore-fracture combinations:intergranular pore-clay mineral shrink fractures,intergranular pore-brittle mineral intergranular fractures and clay mineral intergranular pore-shrink fractures combinations.By injecting Wood's alloy with high-temperature rheological properties into the core at different pressures,it can be observed that the injection of the Wood's alloy in the different pore-fracture combinations shows orderliness with the increase of injection pressure,and the filling priority of the intergranular pores and fractures is obviously higher than that of the clay mineral-related pores and fractures,and the injection efficiency of Wood's alloy shows an obvious parabolic pattern of rapid increase first,followed by a slow increase that tends to be stable eventually.Based on the properties of Wood's alloy and crude oil,the injection pressure was equivalently transformed to simulate the microscopic filling process of tight oil under stratigraphic conditions,and accordingly the pore and fracture sequence filling model of a tight reservoir was established.Under the condition of high source storage pressure difference,the tight oil can be filled into the nanoscale intergranular pore-shrink fractures of clay minerals,and with the decrease of source storage pressure difference,the tight oil is gradually difficult to be filled into the nanoscale pore and fractures.When the source storage pressure difference is reduced to the lowest,the tight oil can only enter the micron-sized intergranular pores and the well-connected mould pores through the wide intergranular connecting throat by means of osmosis.This study combines the fluid injection and visualization techniques for the multi-scale evaluation of reservoir space in tight reservoirs,which is of great significance for the evaluation of microscopic sweet spots and efficient development of tight reservoirs.

The Baima structure belt in the southern part of Fuling shale gas field has experienced many periods of structural movements since the Lower Paleozoic marine shale gasification,and the structural deformation is complicated and different,which has a controlling effect on the gas content of shale gas reservoirs,making the formation mode diverse and restricting the process of exploration and development.This paper analyzes the structural characteristics and evolution process of the Baima structure belt through 3D seismic interpretation,combined with a series of cores and drilling and logging data,and establishes three modes of shale gas enrichment and reservoir formation on the basis of these data.The study shows that:(1)the Baima structure belt mainly develops north-east oriented structures,and exhibits different deformation characteristics of vertical stratification and east-west stratification.Vertically,it is divided into four sets of upper,middle,lower,and Precambrian structural deformation layers by three sets of sliding layers,namely,the Cambrian Qinjiamiao Formation Salt Bed,the Silurian Longmaxi Formation Mud Shale Bed,and the Triassic Jialingjiang Formation Salt Bed.The plane from west to east can be divided into a fold deformation zone and a wide and slow oblique zone.(2)The late Yanshan period is an active period of structural deforma-tion,and the Jiangnan-Xuefeng orogeny produces extrusion from the south-east to the north-west,forming the main north-east oriented tectonic structure of the Baima structure belt.Himalayan period for the structural transformation and finalization of the period,the Indo-European plate collision and the Tibetan Plateau to the east to escape the remote effect caused by the Sichuan Basin counterclockwise rotation,in the eastern part of the Sichuan region for the performance of the right-handed shear,the development of slip shear zones.The Baima structure belt is extruded in the east-west direction,and the first existing northeast structure is modified,and then it gradually turns into the north-south direction.(3)The Baima structure belt can be classified into three shale gas enrichment and storage modes:low-pressure crushed backslope type,normal-pressure wide and slow sloping type,and normal-pressure gentle sloping type.Among them,the shale gas enrichment and preservation conditions in the south slope of Baima are better,with high gas content in a single well.The core and the east wing of the Baima syncline are followed,and the gas content of a single well is higher.The north wing is poor,and the gas content of a single well is slightly lower.The Shimen-Jinping anticline belt is unfavorable for shale gas enrichment and preservation.

The Jurassic Lianggaoshan Formation shale is a key exploration interval in the Sichuan Basin,but its pore structure and shale oil mobility are still unclear.In order to reveal the reservoir space characteristics and the mobility of shale oil in the Lianggaoshan Formation,this paper divided lithofacies types according to sedimentary structure and mineral composition.Basic geochemical characteristics were obtained by total organic carbon determination,rock pyrolysis and vitrinite reflectance experiments.The porosity and pore structure were characterized and evaluated by means of field emission scanning electron microscopy,nuclear magnetic resonance,low temperature nitrogen adsorption and high pressure mercury injection.The difference in reservoir space characteristics between different rock phases was also compared.With a centrifugation time of 3 h and centrifugation speed of 11 000 r/min,quantitative evaluation of the mobility of shale oil with different lithofacies was carried out by NMR centrifugation and the influential factors are clearly defined.The evaluation model of movable oil quantity logging was established and.the favorable rock facies was selected.The results show that:(1)The TOC of Lianggaoshan Formation shale is mainly between 0.15%～2.95%,the Ro is between 1.06%～1.68%,and the shale is in the mature-high mature stage.After the recovery of light hydrocarbons,the change range of S1 was 0.03 mg/g～3.32 mg/g.The mineral types are mainly clay minerals and quartz.The developed lithofacies are lamellar clay shale facies,lamellar felsic shale facies,lamellar mixed shale facies and massive silty mudstone facies.(2)Shale reservoir space types are mainly clay mineral intergranular pores,organic matter pores,in addition to quartz dissolution pores,interparticle pores,pyrite intergranular pores and microfractures.The porosity is between 1.15%and 4.71%.The shale has a wide pore size distribution.The pore volume is mainly contributed by mesopores and macrop-ores smaller than 200 nm.Laminated clay shale has the best physical properties(3)the movable oil content of the Lianggaoshan Formation shale ranges from 0.25 mg/g to 3.26 mg/g,and the movable oil rate ranges from 5.13%to 44.8%.Lamellar clay shale has the best mobility,and massive silty mudstone has the worst mobility.TOC,clay mineral content and porosity are the key factors controlling movable oil content in the Lianggaoshan Formation.Based on these three factors,a mobile oil quantity pre-diction model is established and verified.Laminated clayey shale is preferred as the key exploration object of the Lianggaoshan Formation,which is indicative of the exploration and development of shale oil in the Sichuan Basin.

The microscopic occurrence and mobility of oil in shale matrix pores are the key factors that restrict the efficient exploitation of terrestrial shale oil.This paper carried out quantitative characterizations on the amount,proportion,distribution and mobility of oil with different states in shale matrix pores,and theoretically established a series of models evaluating adsorbed,free and mobile amounts,and oil-adsorbed proportion(i.e.,adsorption ratio equation).A method based on satura-tion-centrifugation-nuclear magnetic resonance tests was established to evaluate the microscopic occurrence and mobility of pore oil.The aforementioned models and methods have been applied to the Shahejie Formation shale oil reservoir in the Dongying Sag,Jiyang Depression,Bohai Bay Basin,and revealed the microscopic occurrence and mobility of n-dodecane in shale matrix pores at 20℃and atmospheric pressure.It is concluded that:(1)the amounts of adsorbed and free oil in organic-rich shales are generally higher than those in organic-bearing shales,and the ratio of adsorbed oil to free oil is mainly between 1 and 2.The storage spaces of adsorbed and free oil in different types of shales are obviously diverse.(2)The average density of adsorbed oil of organic-rich shale(0.8331 g/cm3)is slightly higher than that of organic-bearing shale(0.8067 g/cm3).The average thickness of adsorbed oil of organic-rich shale(1.7475 nm)is about 3 times that of organic-rich shale(0.5734 nm).It shows that the organ-ic-rich shale has a stronger oil-rock interaction.(3)The minimum pore diameter of storing free oil(dmin)is equal to the product of the average thickness of adsorbed oil and the pore shape factor.The dmin of organic-rich shale is of 3.5～10.5 nm,and pores of mainly storing free oil(mass ratio>70%)have a diameter of about 100 nm.The dmin of organic-bearing shale varies from 1.1～3.4 nm,and pores of mainly storing free oil have a diameter of about 30 nm.(4)The mobility index of oil in organic-rich shale(mean 6.24 mg·g-1·MPa-1)is higher than that in organic-bearing shale(mean 5.20 mg·g-1·MPa-1),and pore oil has a better mobility when the ratio of adsorbed oil to free oil is about 1.5.(5)Based on the oil-rock interaction,the coupling relationship of the oiliness and storage space of shale with the mobility of shale oil are established,and the internal relation between them is described mathematically,which will lay a theoretical foundation for discovering high-quality shale oil reservoirs.

To clarify the distribution characteristics of laminas and cracks in continental shale in the Yanchang Formation of the Ordos Basin,a high-definition camera,super depth of field microscope,IPP software,fractal geometry,Monte Carlo simulation and other means were used to observe and characterize the laminas and cracks of continental shale samples in the Chang 72 oil group.Bright and dark laminas were classified,and the mineral components of bright and dark laminas were compared by X-ray diffraction.The thickness distribution of bright and dark laminas at macro,20 times and 50 times magnification were respectively analyzed,and the distribution rules of average laminar thickness of different thickness classes(below 1 mm,1～10 mm and above 10 mm)were analyzed.The distribution characteristics of crack width,spacing and dip angle were characterized,and a two-dimensional mesoscopic structure model of continental shale was established based on the distribution rules of different types of laminas.The results show that:(1)The minerals in the bright lamina are mainly brittle minerals(80%),such as quartz and feldspar,while the dark lamina is mainly composed of 40%brittle minerals and 40%clay minerals.(2)The fitting result between total laminas thickness and quantity of continental shale laminas follows an exponential function,the fitting between bright laminas thickness and quantity of bright laminas follows a power function,and the fitting between dark laminas thickness and quantity of dark laminas follows a logarithmic function.(3)With increasing observation scale,the frequency of thin laminas(below 1 mm)increases,and the frequency of medium laminas(1～10 mm)and thick laminas(above 10 mm)decrease.There is a linear relationship between the logarithm of different kinds of laminar thickness classes and corresponding average laminar thickness.The distribution of laminar thickness has a fractal feature.(4)The crack width is distributed in the mesoscopic range,with a mean and standard deviation of 0.271 mm and 0.114 mm,respectively,which is relatively concentrated.The mean and standard deviation of crack spacing are 8.115 mm and 8.448 mm,which is relatively uniform.The fitting result between the absolute value of the crack dip angle and the quantity of cracks follows a logarithmic function.

The shale revolution has weaned the US from its dependence on imported oil and gas to become a net exporter.This paper reviews the history of the shale revolution in the United States,summarizes the characteristics of shale oil and tight oil and gas,analyzes the development status of the shale oil and gas revolution in China,and puts forward the basic geological theory of shale oil and tight oil and gas.The research shows that:(A)The United States has advantages such as good resource endowment,strong scientific and technological innovation ability,huge investment capacity,and strong engineering construction capacity,and has already realized the shale revolution.China's shale revolution is now under way.(B)Compared with conventional oil and gas,shale oil and tight oil and gas have different accumulation modes and development methods.They have the characteristics of continuous large-area distribution,self-sealing oil and gas accumulations,huge development and production engineering,and the"distributed"characteristics of oil and gas field production can flexibly cope with the characteristics of production reduction and low recovery.(C)Seven conditions need to be met for the further production of shale oil and gas in China:These are(1)Clear resources;(2)Mature horizontal well and fracturing technology;(3)The cost is controllable;(4)The engineering space of enhanced oil recovery in the late stage is large;(5)Meet environmental requirements;(6)Adequate capital investment;(7)Strong engineering construction ability.(D)The whole oil and gas system has a sequence of conventional oil and gas,tight oil and gas and shale oil and gas.Shale oil and gas and tight oil and gas reservoirs have the basic characteristics of tight reservoirs,complex fluid composition and phase state,and diverse reservoir driving modes,and we are faced with the problem of unclear reservoir geological and flow models.It is necessary to carry out further theoretical research of the whole oil and gas system,and vigorously develop sweet spot evaluation technology and fracturing technology.

陆相页岩油是一个全新领域,近期的勘探实践已在鄂尔多斯盆地、松辽盆地、渤海湾盆地、准噶尔盆地、柴达木盆地等不同页岩层系取得了重要进展,截止2022年底,页岩油探明、控制、预测三级地质储量达44亿t,2022年产量达318万t.页岩油勘探理论和技术也取得了一系列进展,创新了有机母质类型分析与有机质生排烃实验、储层表征技术、页岩油赋存状态与含油性分析、保压取心与现场测试等页岩实验测试分析技术,基本上能满足页岩油相关实验测试要求;在细粒沉积与有机质富集机理、陆相页岩纹层结构与组合类型、储层孔缝结构与储集性、页岩油富集机理取得了一系列新的认识,指导了重点地区选区选带评价研究.研发了烃源岩品质测井评价、储层品质测井评价、工程品质测井评价、岩石物理敏感参数分析和定量预测、多任务学习储层参数预测、各向异性地应力预测、水平井地震地质导向评价、富集层(甜点)综合评价等技术,并推广应用,在页岩油储量提交、甜点区优选、水平井部署、随钻导向预警和钻完井工程改造方面提供了重要且面向全周期的技术支撑.但陆相页岩油规模勘探与效益开发目前还面临诸多挑战,必须建立全新的研究内容与研究重点,特别需要把研究精度升级并要加强微观研究,加强固/液/气多相多场耦合流动机理研究,加强多学科交叉研究等,以建立页岩油成藏新学科.

从全球油气勘探发展趋势来看,深层—超深层天然气勘探已经成为化石能源勘探未来的主战场.不仅常规碳酸盐岩和碎屑岩领域,非常规的页岩气和煤层气等领域也进入深层—超深层勘探阶段.前期,我国在深层天然气勘探中形成了一批具有开创性的理论和技术,指导了很多具有战略意义的商业发现,提升了我国能源的保障能力.但同时在面向更深层的勘探目标时,还面临着新的地质、工程等方面的挑战,还有很多世界级难题需要攻关.本文系统回顾了近年来,我国在深层—超深层碳酸盐岩、碎屑岩、页岩气、煤层气等领域勘探中取得的成就,重点总结了深层—超深层不同领域天然气成藏条件与主控因素的研究进展,从资源评价、储层发育与保持机理、油气成藏与富集规律、地球物理和工程技术等方面,提出了深层—超深层天然气勘探面临的主要问题与发展建议,以期能为加快我国深层—超深层天然气勘探提供参考.

本文详细阐述了全球尤其是北美页岩气开发现状,论述了Marcellus与Haynesville页岩气区的主要特征,认为持续技术创新、高效经营管理模式、多元产业扶持政策是美国页岩气飞速发展的主要驱动力,对我国页岩气的开发具有良好的借鉴作用.作者系统梳理了中国页岩气近 20 年的探索攻关与实践历程,认为历经评层选区、开发试验、示范区建设、海相页岩气规模开发4 个阶段,国内页岩气开发取得了重大成就,建成川南、涪陵等中深层页岩气大气田,实现了海相页岩气规模效益开发,2022 年产量达 238 亿方,成为我国天然气重要的供应来源,同时深层页岩气产能建设稳步推进,新区新层系勘探也取得重大突破.在深入分析我国页岩气地质与资源特征的基础上,文章论证了我国具备年产 500 亿～800 亿的开发潜力,但需要从完善页岩气立体开发配套技术、持续优化页岩气地球物理评价技术、加快钻井与压裂工程技术迭代升级、加大新层系新领域的勘探评价力度4个方面持续攻关.

鄂尔多斯盆地三叠系延长组长73亚段沉积的富有机质泥页岩中,频繁发育的纹层导致页岩层系非均质性强,进而对泥页岩的储集特征及含油性造成影响.本文基于典型的纹层页岩样品,利用游标卡尺对岩心上的纹层进行定量测量,结合显微镜下薄片鉴定、总有机碳测定、X射线衍射矿物分析及岩石热解实验,对长73亚段页岩纹层的发育特征、纹层类型划分及纹层在单井上的纵向展布规律进行了研究.研究结果表明,宏观岩心上发育的纹层单层厚度一般分布在0.4～5.0 mm,纹地比(纹层总厚度/统计段岩心长度)介于5.7％～16.8％,纹层发育频率非均质性强.显微镜下依据纹层沉积构造的形态划分为6类,分别为3种具有连续形态沉积特征的平直型纹层、波纹型纹层、粒序型纹层及3种非连续形态沉积特征的透镜状纹层、斑状纹层、弱纹层,不同形态纹层页岩的矿物组成及有机质丰度差异明显.依据纹层内部的微观物质组成将其类型主要划分为有机质纹层、长英质纹层及凝灰质纹层;按照不同纹层垂向的叠置规律,将纹层组合划分为均质泥岩、长英质纹层型页岩与凝灰质纹层型页岩.单井上,纹层分布具有非均质性,不同纹层的发育频率与黏土矿物含量、TOC及OSI的变化呈一定的规律性变化.

湖相重力流是目前沉积学研究的热点与难点,也是致密油、页岩油富集的有利场所,鄂尔多斯盆地庆城油田三叠系延长组作为致密油、页岩油的典型代表已显示出巨大的勘探开发前景.然而,由于湖相重力流砂体分布认识不清,导致油田并未达到预期的开发效率.本文采用支持向量机(SVR)的机器学习方法,先优选频段再优选属性,建立分频属性与测井解释砂体厚度的非线性映射关系,实现了致密砂岩的定量预测.研究结果表明,低频地震属性适合预测厚层砂体,高频地震属性适合预测薄层砂体;采用机器学习的方法,将不同频率的地震属性智能融合,能够兼顾预测不同厚度砂体,既提高了地震属性的解释精度,又降低了地震解释的多解性,实现了砂体厚度的定量预测.检验结果显示,智能融合属性与砂体厚度的分布趋势与值域区间基本一致,智能融合属性预测砂体分布的可靠性明显提高,与测井解释砂体厚度的相关性由0.60提高至0.79,大多数井点处预测的砂体厚度误差小于5 m.继而,根据融合属性与测井解释,刻画了研究区的沉积微相展布特征:研究区目的层发育湖底扇沉积,细分为分支水道、朵叶主体、朵叶侧缘、滑塌体与朵叶间/水道间5种沉积微相;砂体主体呈扇形连片式沉积,厚度顺物源方向逐渐减薄;分支水道呈窄条带状树形分叉,下切发育于朵叶体之上;朵叶体沉积为研究区的沉积主体;滑塌体为湖底扇前端失稳滑塌形成的小规模孤立砂体,长轴方向多平行于湖底扇前端.研究成果对油田下一步高效开发具有重要意义.

南华北盆地晚古生代时与鄂尔多斯盆地同属于华北克拉通盆地的一部分,发育广泛的石炭-二叠系煤系地层.其中,太原组不仅是重要的烃源岩层,而且具备良好的致密砂岩气等非常规天然气成藏条件.然而,关于砂岩储层的研究目前尚处于早期阶段,砂岩储层的特征、致密成因和天然气充注特征等一系列关键性问题仍然缺乏详细的研究.本文综合利用铸体薄片、扫描电镜、物性分析、X射线衍射、流体包裹体等实验测试方法研究了南华北盆地太康隆起太原组致密砂岩储层的岩石学特征、成岩特征及成岩作用下孔隙度演化历史,确定了储层致密时间和成因,同时结合地层埋藏史-热演化史,恢复了致密砂岩储层中天然气的充注过程,最终确定了砂岩储层的致密-气体充注之间的耦合关系.研究结果显示:太原组致密砂岩储层主要经历了压实、胶结和溶解等多种成岩作用,当前处于中成岩阶段B期,孔隙类型以次生溶蚀孔隙、黏土矿物晶间微孔和微裂缝为主.通过定量分析不同类型成岩作用对孔隙度的影响,确定压实作用是导致储层致密最主要的因素,造成储层原生孔隙度从38.6％降低了31.01％,黏土矿物、碳酸盐矿物及硅质胶结作用仅使孔隙度损失7.27％,长石、岩屑等颗粒溶蚀作用增孔能力有限(仅为3.28％);孔隙度演化恢复结果表明太原组砂岩储层在中成岩A期的晚期(晚三叠世)开始进入致密阶段.通过对流体包裹体的类型和成分分析,确定太原组砂岩经历过单期次的气体充注过程.含烃盐水包裹体均一温度与地层埋藏史-热史对比结果表明气体充注对应地质时间为229～213 Ma,对应地质历史时期为晚三叠世,与储层致密化时间基本一致,表明太原组砂岩储层属于"边致密边成藏"型储层.

通过对桂北地区猫儿山剖面下寒武统清溪组6个海相页岩和2个粉砂质泥岩样品的总有机碳含量(TOC)、矿物组成和高压甲烷等温吸附的测试,评价了桂北地区下寒武统清溪组海相页岩的甲烷吸附性能,探讨了该地区下寒武统清溪组海相页岩甲烷吸附性能的影响因素.实验结果显示,桂北地区猫儿山剖面下寒武统清溪组样品具有较高的TOC值,其平均值为6.57％.矿物组成特征表明,研究区样品中石英含量相对较高,其分布范围为42.3％～69.1％,是其主要组分.清溪组泥页岩样品也具有较高的黏土矿物含量,其分布范围在12.4％～32.7％之间,平均值为20.8％,是次要组分.其他矿物主要包括长石、云母和菱铁矿.通过线性拟合分析,研究区清溪组页岩甲烷最大绝对吸附量与TOC含量之间线性回归方程拟合的R2为0.8328,表明研究区页岩样品的TOC对甲烷最大绝对吸附量有着直接影响,甲烷吸附能力与TOC含量呈正相关.同时,TOC标准化处理后的甲烷最大绝对吸附量与黏土矿物之间也存在较好的正相关性.TOC含量为影响桂北地区猫儿山剖面下寒武统清溪组页岩甲烷吸附能力的主要因素,黏土矿物含量次之,影响相对较弱.此外,通过对比发现,相同TOC含量下,该地区清溪组页岩的最大吸附量与四川盆地龙马溪组页岩基本一致,表明研究区清溪组页岩具有与龙马溪组页岩相似的甲烷吸附性能.

为明确桂中坳陷北部下石炭统鹿寨组一段成藏条件,评价区块资源潜力,利用录井、地震、实验测试等手段,系统分析页岩气成藏地质特征,并采用静态法对研究区页岩气资源量进行计算.研究表明:鹿寨组一段页岩有机质丰度中等(TOC含量在0.49％～5.15％)、类型好(有机质类型为II1～II2型)、热演化程度适中(热成熟度在2.2％～2.9％);储层脆性指数高(51％～94％),物性条件较好(孔隙度在3.12％～5.02％,渗透率在0.0005～0.161 mD),孔径多小于400 nm;储层孔隙类型以有机质孔和溶蚀孔为主,孔隙比表面积以微孔贡献为主,孔体积则主要由微孔和介孔贡献,微孔发育主控因素包括TOC和黏土矿物,而介孔发育主控因数为黏土矿物;现场总含气量平均1.73 m3/t,甲烷含量高达95％,为高热值干气;甲烷等温吸附绝对吸附量在1.07～3.67 m3/t,页岩吸附能力强;研究区页岩气藏埋藏深度多在1000～3000 m,顶板黄金组和底板尧云岭组岩性以(泥质)灰岩为主,岩性致密,累计厚度分别可达720 m和490 m,区内逆冲断层封堵性好,构造变形程度较低,岩浆活动较弱,温泉水循环深度多在800～1000 m,水文地质开启程度低.研究区沙坪复向斜页岩气地质资源量为255.2×108 m3,技术可采资源量为38.3×108 m3,技术可采资源丰度0.45×108 m3/km2.结论认为,桂中坳陷北部残留向斜核部鹿寨组一段页岩生烃基础较优越、储集空间发育、含气性高、保存条件较好、埋深适中及资源丰度较高,是页岩气勘探开发有利目标.

机器学习算法已经成为工程领域建模的有力工具,这些方法通过使用复杂结构或多重非线性变换从更高的维度拟合多个变量之间的非线性关系,适用于解决工程中由于变量关系复杂,传统物理模型或经验模型无法有效解决的问题.由于传统的测井资料解释方法是基于岩石物理机理和模型为基础,需要许多假设条件,在实际应用中存在一定偏差.因此,利用机器学习算法对测井资料进行处理和解释,尤其是对储层流体进行识别具有重要意义.现有的储层流体识别方法没有充分挖掘测井数据多维空间的关联性.此外,还存在储层类别分布严重不均衡、相似物性储层的识别容易混淆的问题.本文针对储集层流体识别任务提出了基于机器学习算法的高效解决方案.采用长短期记忆网络(LSTM)和卷积神经网络(CNN)分别表征测井曲线时序特征以及多条测井曲线之间的相互关联关系;考虑到油气储集层识别任务的类别分布不均衡性问题以及不同储层的价值排序有所差异,本文采用加权交叉熵损失函数,在模型训练中更注重学习少样本类别的特征,进一步提升含油储层的识别准确度.依据储层物性差异和相似度,设计了多层级储层流体识别方法,将LSTM和CNN的模型结构应用于层级II(含油储层、含水储层和干层)和层级III(油层、油水同层、差油层和水层、含油水层)的识别.本方法在真实油田测井数据上加以验证,其中数据分布极不均衡,高价值的含油类储层占比9％,符合真实工业场景.通过大量对比实验证明,LSTM和CNN的并行网络结构能够充分挖掘测井数据多维空间的相关特征;加权交叉熵损失函数显著提高了高价值含油储层的识别准确度,多层级储层流体识别方法对于物性相近的易混淆储层,如油水同层和含油水层的区分更加准确.实验结果表明,该方法能有效克服储层流体识别任务中的各种问题,对于帮助地质专家和工程师寻找地下储层,完成储层评价具有一定的实用价值.