The Lower Cambrian Qiongzhusi Formation in the Sichuan Basin exhibits significant shale gas resource potential, with major exploration breakthroughs achieved in the Deyang-Anyue rift sag. However, the complex hydrocarbon accumulation processes under multi-phase tectonic activities have constrained the optimization of shale gas enrichment zones and efficient exploration and development. This study focuses on typical Qiongzhusi Formation shale gas reservoirs in the Zizhong-Weiyuan area of the Deyang-Anyue Rift Sag. Through petrographic observations of fracture veins, fluid inclusion thermometry, laser Raman analysis, and basin modeling, the evolutionary processes and differences in shale gas accumulation in the Zizhong-Weiyuan area were elucidated. Results reveal three distinct stages of fracture vein development in the Cambrian Qiongzhusi shale: Stage I veins formed during the late Caledonian movement (ca.420~405 Ma), containing abundant primary bitumen inclusions indicative of peak oil generation; Stage II veins developed during the Indosinian movement (ca.235~215 Ma), characterized by both primary bitumen and methane inclusions reflecting high-to-over mature shale conditions; Stage III veins formed during the Yanshanian-Himalayan reservoir preservation and adjustment stage, predominantly hosting primary methane inclusions. The Weiyuan and Zizhong areas exhibit vein formation during the Late Cretaceous (ca.75~60 Ma) and Eocene (ca.45~35 Ma), respectively. This may due to that the Weiyuan area is situated in the aulacogen margin, whereas the Zizhong area is located in the inner zone of aulacogen. Therefore, the Weiyuan area began to uplift ~10 Ma before the Zizhong area during the Yanshannian orogeny. Additionally, the Zizhong area benefits from superior basal sealing by the Maidiping Formation, forming an effective gas containment system. Its location on the intra-sag slope belt features less developed faults and fractures compared to the Weiyuan anticlinal region. These combined factors contribute to the overall superior gas-bearing characteristics of the Qiongzhusi Formation in the intra-sag Zizhong area relative to the sag-margin Weiyuan area.

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.

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.

Organic matter is the basis of shale gas generation,and the study of Quaternary Pleistocene climate change in the Qaidam Basin and its effect on organic matter enrichment is crucial for the exploration and development of biogenic gas in the Qaidam Basin.In this paper,the Quaternary shale in the Qaidam Basin is taken as the research object,and Quaternary Pleistocene climate change is clarified in terms of paleo-moisture and paleo-temperature through organic carbon analysis and main and trace element experiments.Then,the influence of climate change on organic matter enrichment is analyzed from two perspectives:biological productivity and organic matter preservation.Finally,the Quaternary Pleistocene organic matter depositional pattern of the Qaidam Basin is established.The results show that(1)in the early-middle Quaternary Pleistocene,the climate was cool and humid,the herbaceous plants were luxuriant,and rich in cellulose,hemicellulose,sugar,starch and pectin,which improved the biological productivity of the surface layer of the water column.The amount of precipitation was high,and the stratification of the water column was good.The strong stratification of the water column also enhanced the reduction level of the lower layer of the water column,which is favorable for the preservation of the organic matter deposited from the upper layer and thus favors the enrichment of sedimentary organic matter.Additionally,relatively low temperatures inhibit the activities of methanogenic bacteria,which is also conducive to the preservation of organic matter.(2)In the late Pleistocene,under the Neo-tectonic Movement,the Tibetan Plateau uplifted,the climate became arid,and the temperature increased,leading to an increase in the proportion of woody plants and a decrease in the amount of nutrients available to methanogenic bacteria,decreasing the biological productivity of the surface layer of the water column.On the other hand,the stratification of the water column was weakened.The mixing of oxygen-rich water in the upper layer and oxygen-poor water in the lower layer results in the level of reduction of the lower layer of the water column being significantly lowered.The sedimentary organic matter that settled from the upper layer was easily destroyed,which was unfavorable for the preservation of sedimentary organic matter.Additionally,when the temperature was relatively high,methanogenic bacteria consumed a large amount of organic matter,which was also unfavorable for the preservation of organic matter.The research results have important theoretical and practical significance for the exploration and development of biogenic gas in the study area.

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.

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.

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.