Siliceous minerals of the Dengying Formation in the Gaoshiti–Moxi area in the central Sichuan Basin exhibit four types of quartz crystals (cryptocrystalline quartz, chalcedony, microcrystalline quartz, and megacrystalline quartz) and three structural types: cryptocrystalline, microcrystalline, and mosaic (laminated mosaic, window-hole interrupted mosaic, and arc-laminated mosaic). Siliceous minerals have a great influence on the storage performance of the reservoirs in the Dengying Formation. According to the petrophysical parameters of the Dengying Formation and porosity intersection diagrams, the siliceous dolomite and the reservoirs have low impedance characteristics, which makes it difficult to distinguish between them and leads to difficulties in the characterization and prediction of the reservoirs. The transverse wave velocity is favorable for reservoir characterization. Currently, the main method used to estimate the transverse wave velocity is petrophysical modeling, which establishes a relationship between the elastic and physical parameters of the reservoir. In this paper, the siliceous minerals in the dolomite in the study area are regarded as solid inclusions, and the calculation method of the rock matrix modulus is improved by using solid replacement. Then, an improved petrophysical model is constructed by combining the KT (Kuster–Toksöz) model, the DEM (Discrete Element Method) model, the Gassmann equation, and the Wood equation. The transverse wave velocity is estimated using the improved model under the constraint of the longitudinal wave velocity. The shapes of the transverse wave velocity curves obtained by the improved model and the deviations from the measured velocities are significantly better than those of the Xu–Payne model and other models. The results show that the improved model can effectively estimate the transverse wave velocity of the reservoir in this area, which provides a basis for future reservoir predictions in this area.

通过岩心观察、镜下鉴定、连井沉积相对比等研究,厘定了四川盆地高石梯地区震旦系灯影组四段微生物碳酸盐岩微相组合,并对储层主控因素进行分析.结果表明:(1)四川盆地高石梯地区震旦系灯影组四段沉积微相为微生物丘与颗粒滩,垂向上颗粒滩向上演化为微生物丘,识别出丘基-丘核-丘翼、丘基-丘核-丘盖、丘基-丘核及滩间海-风暴滩4种沉积序列;平面上微生物丘含量由台缘向台内逐渐降低且整体沿台缘带呈西薄东厚的特征.(2)储层主控因素为丘滩复合体和风化壳岩溶作用,丘滩复合体为储层发育提供良好的物质基础,风化壳岩溶作用极大地改善储层的物性,而埋藏热液作用对储层发育的贡献具有两面性.(3)主要存在2类储层,沉积主控型储层,发育于灯影组四段下部;表生岩溶型储层,发育于灯影组四段上部.研究成果为丰富和完善高石梯地区微生物碳酸盐岩微相分类与储层主控因素分析提供基础材料和研究实例,可为后续勘探开发工作提供借鉴.

In contrast to the widely used sequence stratigraphic models for passive continental margins, the stacking patterns of strata within epeiric seas, which are influenced by regional tectonic activity, may display opposing characteristics during the same geological period. These variations serve as a record of basin evolution and also affect the accumulation of hydrocarbons within the strata. Our study investigated the development potential of the deep Longmaxi Shale in the southern Sichuan Basin by examining the sequence stratigraphy and sedimentary fill patterns. Using a combination of core observation, well-logging data analysis, and 3D seismic profile interpretation, we aimed to gain an understanding of the sedimentary fill history of the Longmaxi Shale during the Early Silurian. Our analysis revealed that deglaciation and regional tectonic events affected the sequence stratigraphy, resulting in unconformities that were identifiable using seismic data and wireline logs. Through an analysis of thirty wireline logs and two seismic profiles, we identified two third-order sequences suggested in the Lower Longmaxi Formation. Within the two third-order sequences were five systems tracts, with the first exhibiting a complete cycle of sea-level change and the second cycle being incomplete due to regional tectonic events. The graptolite succession on the upper Yangtze Platform provided a temporal view of the sequence stratigraphy and sedimentation rates of the Longmaxi Shale. The thickness trends of the systems tracts reflected the interplay of short-term eustasy fluctuations, subsidence, and uplift. Our analysis suggests that regional subsidence played a significant role in the deposition of the second transgressive systems tract (TST) in the Weiyuan and Luzhou areas, which represents a promising target for shale gas exploration, in addition to the first TST. However, the Changning area experienced a relative sea-level decrease due to the intense uplift of the Qianzhogn Paleo-uplift and the increased supply of sediment and is interpreted as a highstand systems tract (HST); it is not considered to have shale gas exploration potential.

Carbonate reservoirs in the Sinian Dengying Formation, central Sichuan Basin, are a hot spot for hydrocarbon exploration and development in deep and ultra-deep sequences in China. Multi-type and multi-scale natural fractures are widely seen in the Dengying reservoirs, and of significant impacts on the seepage flow pattern and well productivity. In this study, the genetic types and developmental characteristics of natural fractures in the fourth member of Dengying Formation (Deng 4 Member), Gaoshiti-Moxi area, are clarified utilizing the cores, thin sections, image logs, experimental tests and production testing data. Major geological factors controlling the development of natural fractures are used to analyze the impact of natural fractures on well productivity. Results show that natural fractures in the Deng 4 Member reservoirs in Gaoshiti-Moxi area are mainly of tectonic and diagenetic types. The tectonic fractures can be divided into shear fractures and tension fractures, and the diagenetic fractures are mainly bedding fractures and stylolites, among others. The shear fractures dominate the Deng 4 Member reservoirs, and are mainly of high-angle ones and striking in the NNW-SSE, nearly EW, NE-SW and nearly SN directions. Factors controlling the shear fracture effectiveness include the timing of fracture formation, cementation, dissolution, fracture occurrence and current in-situ stress. The shear fractures in NNW-SSE and nearly EW orientation are more effective than others. The development degree of shear fractures is closely related to the lithology, mechanical layer thickness and faults. The shear fractures are more highly developed in micritic dolomites, and their density decreases and scale enlarges along with the increasing thickness of mechanical layers. The shear fractures near the main strike-slip faults, in particular within the tip and superimposed part of faults, are better developed. The development degree and effectiveness of fractures jointly determine gas well productivity. The effective fractures in different occurrences and scales can form fracture network, and get relatively isolated pores interconnected, which greatly improves the seepage capacity of reservoirs and elevate well productivity. In the Deng 4 Member reservoirs of Gaoshiti-Moxi area, the shear fractures in NNW-SSE and nearly EW orientation are of stronger ability to enhance reservoir permeability, and make greater contribution to the improvement of well productivity.

Shale pore systems are the result of the geological evolution of different matrix assemblages, and the composition of gas shale is considered to affect the pore systems in shale reservoirs. This study aimed to investigate the impact of both organic and inorganic constituents on the shale pore system, including specific surface area (SSA) and pore volume in Wufeng–Longmaxi Shale. Multiple linear regression (MLR) was employed to examine the contributions of different components to shale pore structure. The pore structure parameters, including pore SSA and pore volume, were obtained by gas adsorption experiments in 32 Wufeng–Longmaxi Shale (Late Ordovician–Early Silurian) samples. Both pore SSA and pore volume were calculated by the density functional theory (DFT) model on shale samples, and the pore types were determined by high-resolution field emission scanning electron microscopy (FE-SEM). The results of the X-ray diffractometer (XRD) analysis indicate that the Wufeng–Longmaxi Shale is dominated by quartz, clays, carbonates, feldspar, pyrite, and organic matter. Four models were made using SPSS software, all of which showed significant correlation between shale pore size and organic matter (OM) and clays. The content of organic matter played the biggest role in determining the size and structure of the pores. Although the content of quartz is the highest and serves as a rigid skeleton in shale reservoirs, it has complicated effects on the pore structure. In this study, most of the quartz is biogenetic and part of it is transformed from clays in deep shale. Therefore, these two parts of quartz are, respectively, related to organic matter and clays. In essence, the pores related to these two parts of quartz should be attributed to organic matter and clays, which also support the conclusion of the MLR models.

页岩孔隙结构是控制与影响海相页岩储层质量的主要参数之一,对于页岩气资源评估、勘探和开发极其重要.为阐明泸州地区深层五峰-龙马溪组页岩孔隙结构,基于氦气膨胀法测孔隙度、矿物组分分析、TOC测试,采用CO2和N2吸附、高压压汞联合表征页岩全孔径,并与氧化-还原条件、水分、TOC等因素藕合,探讨页岩孔径分布的主控因素.结果表明:页岩中以介孔为主,微孔次之,宏孔较少,平均分别占总孔隙的73％、23％、4％;孔径分布与孔隙体积从五峰组向上先增加后降低;TOC与低孔径孔体积相关性高;水分占据页岩孔隙,大幅降低页岩孔隙体积和表比面积.因此,页岩孔径分布受沉积条件、TOC、水分共同控制.

This study investigated the effect of overpressure on the deep shale pore system in the Wufeng-Longmaxi Formation (WLF), a well-established shale gas reservoir in the southern Sichuan Basin, China. The Y1 well was drilled to explore deeper overpressured sections of the basin. Organic geochemistry, mineralogy analysis, field emission scanning electron microscopy (FE-SEM), and gas physisorption experiments were conducted to analyze the pore system. Results showed that despite strong compaction, deep organic-rich shale retained large pores. Compared to shallow shale, deep shale had a larger organic porosity with a smaller average pore size, although some pore sizes exceeded those in shallow shale. Nitrogen (N2) adsorption indicated that the abundance of organic matter (OM) affected mesoporous volume and specific surface area (SSA), while carbon dioxide (CO2) adsorption experiments suggested that micropores were not influenced by OM abundance. Comparing calculated pore SSA and volume via gas adsorption of shallower and deep shale samples revealed that, under similar OM abundance, pore SSA was nearly identical, but deep shale had a larger pore volume than shallow shale. The preservation of pores, particularly in deep shale, is attributed to overpressure, which protects against collapse; additionally, generated shale gas during thermal evolution of OM serves as pore support.

四川盆地安岳气田须二段致密气储量丰富,地质特征相对复杂,常规 AVO分析方法预测储层含气性分布的精度较低,需要研究采用更加精细的地震预测方法.基于单井岩石物理和正演模型特征分析,采用基于小波变换下的分频AVO反演,优选出优势频段的AVO属性进行融合构建含气性因子,进而对安岳气田须二段有利含气富集区带进行分布预测.结果表明,须二段气层主要表现为Ⅳ类AVO响应异常.优势频段 35～45 Hz的气、水层AVO响应比全频段的AVO响应的差异特征较明显,差异性更大,更易突出含气响应特征;AVO含气性敏感属性为相对横波速度差异、相对泊松比差和流体因子,经融合得到含气指示因子的负异常区域指示含气有利区;井震对比可知优势频段AVO属性的含气性预测效果较好.该方法以期为非常规油气勘探提供技术支撑.

Porosity, total organic carbon content, brittle mineral content, and gas content are now the primary references for classifying and evaluating marine shale gas reservoirs in China. Is there a more effective and appropriate reservoir classification scheme for deep marine shale? The Longmaxi Formation in Luzhou, southern Sichuan Basin, China, is the main object of study. Quantitative analysis and modeling using data from field emission scanning electron microscopy, nitrogen adsorption, and logging were used to characterize organic matter (OM) pore multi-scale development and reveal the relationship between OM pore and the high-quality reservoirs. Microscopic and macroscopic indications from OM pores show that a large number of OM pores were developed in high-quality reservoirs. OM surface porosity occupancy of the high-quality reservoir in the Luzhou area was more than 60%. OM porosity occupancy was more than 50%. The nitrogen adsorption–desorption hysteresis loops demonstrate the development of bottleneck and wedge-shaped OM pores. Characterization of multi-scale pore structure by box dimension, pore volume and specific surface area. It is found that the key to the formation of high-quality reservoirs was the massive development of OM mesopores in siliceous shale and the relatively homogeneity structure, which was conducive to the enrichment and migration of shale gas. Furthermore, the improved model decreased the relative error in predicting the OM porosity by about 32.5%. The use of OM porosity occupancy for high-quality reservoir classification was better, and the results were consistent with geological understanding. OM porosity occupancy showed that the area from Lunanxi to Luzhou to Rongchang to Jiangjin was the key exploration area for high-quality reservoirs in southern Sichuan. This study is expected to provide a new idea for OM pore modeling analysis and deep marine shale gas reservoir classification.

Organic matter (OM)-hosted pores are the primary pore type in the deep shale reservoirs of the Longmaxi Formation, in the Sichuan Basin, China, as well as the main locations for shale gas enrichment. However, the quantitative characteristics of OM pore space are not clear, and there is a lack of characterization methods. In this study, scanning electron microscopy (SEM), mercury intrusion porosimetry, low temperature gas adsorption, and logging data are all used to carry out multi-scale quantitative characterization of OM-hosted pores. The shape factor (F) model, fractal dimension model, and the OM porosity model are improved by combining them with mathematical morphology. The study primarily examines the effect of heterogeneity and the development of full scale pores in the OM pore space of the Luzhou area. The results show that (1) the ideal shape factor (F*) reflects the compaction degree of OM-hosted pores. From macropores to micropores, F* ranges from 0.61 to 0.93 as the shape gradually changes from flattened to round. (2) Shape factor and fractal dimension analyses revealed that the heterogeneity strength of the nanopore structure is mainly controlled by macropores. At the micro level and macro levels, the OM space shows lateral homogeneity and vertical heterogeneity. (3) Compared to the established method, the relative error of the improved model used in this study for predicting OM porosity was reduced by 19%. (4) Compaction and pore structure heterogeneity influence the formation of nanoscale pores in the Luzhou region and these factors also promote the development of mesopores and micropores, respectively. Furthermore, the OM porosities of the dominant shale reservoirs in Luzhou account for more than 50% of the overall porosity. This understanding will be of considerable benefit for evaluating deep shale reservoirs.

Despite the huge gas resources in the shale of the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation in the Sichuan Basin and its periphery, commercial breakthroughs are mainly located inside the basin.The Southeast Chongqing, located in the basin margin transition zone, was intensively deformed by tectonic activities. As compared to the gas enrichment model of the Wufeng-Longmaxi Shale inside the basin, the basin margin transition zone requires better preservation conditions.According to the complicated structure patterns of the Wufeng and Longmaxi Formations in Southeast Chongqing, the preservation conditions are analyzed by the super position of structure evolution, uplift and exhumation, fault development, structural style, roof and floor conditions, and formation pressure. The results show that the basin margin is seriously uplifted and exhumated, with well-developed faults, forming a series of residual structural styles; natural gas leakage in the area close to the exhumation boundary and major faults contributed to the low formation pressure coefficient（less than 1.2）. Sangtuoping syncline and Wulong syncline show good preservation conditions of shale gas because of the relatively less large faults and the far away from the exhumation area. Therefore, the late uplift, exhumation, and fault development are the main reasons for the gas leakage and the change of formation pressure from overpressure to normal pressure across the basin margin. Tectonic deformation is the fundament of current shale gas preservation in the structures of narrow and steep residual anticlines, broad and gentle residual synclines, and residual slopes. Finally, an evaluation standard was established for the preservation conditions of normal-pressure shale gas. According to this standard, favorable target areas are divided for normal shale gas in the study area.

The structural evolution and sedimentary differentiation of the Sichuan Basin in China are complex, with intricate reservoir pore structures that significantly impact shale gas production. This study examines the complexity and heterogeneity of the microscopic pore structures in the deep marine shale reservoir in the Longmaxi Formation. Pore structure characterization techniques are used to compare deep and shallow–medium marine shales, and siliceous and silty shales. The results reveal the factors influencing pore structure and their impact on exploration and development. The key points are as follows: (1) The pore structure of deep siliceous shale is the most complex due to its diverse range of pore development patterns, pore types, and sizes. (2) The box dimension of full pore size is about 1.52 for deep marine shale and 1.46 for shallow–medium shale. Organic matter (OM) content, the degree of pore development, and inorganic mineral content all correlate positively with the complexity of the pore structure in deep marine shale, which affects the formation of high-quality reservoirs. (3) Lateral heterogeneity of pore structures shows strong regional variations in the study area. Heterogeneity is more pronounced in the deep marine shale than in the medium and shallow shale formations. OM mesopores significantly influence the overall heterogeneity of the shale pore system. The deep marine shale reservoir is situated in an area with strong regional variations. The pore structure of high-quality reservoirs is more complex than those of shallow–medium marine shales, displaying notable heterogeneity. Pore structures with fractal dimension values close to that of the shallow–medium formations (box dimensions within 1.5) offer promising targets for the exploration and development of deep marine shale gas.

Hydrothermal fluid is one of the factors controlling Archean buried hill reservoirs in Bozhong 19-6. However, there are no clear studies focusing on the influence of hydrothermal alteration products and their lithological characteristics on reservoirs. Through characterization of the alteration reservoir and construction of a new subtraction model of the logging-rock mechanical alteration degree, the comprehensive uses of core, thin section, and electrical imaging logging data are considered as the research objects with metamorphic and igneous rocks. Thus, the relationship between lithologies with different alteration degrees and reservoir quality is revealed. The study shows that feldspar chloritization and sericitization are the main factors controlling the hydrothermal alteration of the reservoir; the overall alteration degree of igneous rocks is high, and the overall alteration degree of metamorphic rocks is low; the reservoir with strongly altered igneous facies is prone to forming dissolution pores, with strong reservoir inhomogeneity and poor reservoir performance (alteration degree is greater than 15%); the reservoir with weakly altered metamorphic facies is prone to developing fractures and a high reservoir productivity (alteration degree is 0); The reservoirs with altered metamorphic facies are numerous in the formation, spatially diverse in type, and second in reservoir quality only to those in the weakly altered metamorphic facies (alteration degree of 0–15%). This method is expected to provide a reference for quickly finding advantageous reservoirs in the Bohai Sag.

五峰组(O3w)-龙马溪组(S1l)海相页岩是川南下古生界页岩气勘探的主力层系之一,热成熟度是烃源岩和页岩气评价的一项重要指标.由于缺乏镜质体,一直难以建立准确评价下古生界海相页岩热成熟度的方法.共采集33块川南五峰组-龙马溪组岩心样品,用于观察源内固体沥青及笔石表皮体的光学特征,并测试其随机反射率.同时,利用样品中干酪根的拉曼光谱参数分析热成熟度的演化趋势.研究结果表明,相较于源内固体沥青,笔石表皮体来源单一、颗粒较大、特征明显,且垂直层理切面上非粒状笔石表皮体随机反射率(GRor)数值分布更集中,更适合作为反射率测试对象.干酪根的拉曼光谱参数特征表明,热演化过程中GRor与等效镜质体反射率(EqRo)并非单一的线性关系.利用干酪根的拉曼光谱参数为中间变量,建立了通过GRor计算EqRo的方法.计算结果表明,五峰组-龙马溪组页岩在长宁、泸州-大足和威远地区的热成熟度依次降低,EqRo分布范围分别为2.99％～3.91％,2.87％～3.54％和2.46％～3.03％,平均值分别为3.44％,3.22％和2.77％.长宁西部出现了异常高成熟度区域,需要评价其对页岩气勘探的影响.

The deeply buried carbonates in the Sinian Dengying Formation are one of the crucial hydrocarbon exploration targets in the central Sichuan Basin of China, and are characterized by strong heterogeneity in reservoir quality, which is closely related to natural fractures. To reveal the impacts of natural fractures on the reservoir quality of Deng-4 Member carbonates in the Gaoshiti-Moxi area, the types, characteristics, and factors controlling the development and effectiveness of fractures, were systematically analyzed based on core samples, thin sections, image logs, petrophysical measurements, and drill stem tests. Tectonic shear fractures are the dominant fracture type affecting the petrophysical properties of the Deng-4 Member reservoirs. The distribution and development of shear fractures are mainly controlled by lithology, mechanical layers and faults. Factors influencing the effectiveness of shear fractures include the timing of fracture formation, cementation, dissolution and current in-situ stress. Early-formed shear fractures are more susceptible to filling during subsequent cementation, whereas fractures formed at later stages are rarely filled and, also, have the potential to be solution-enlarged by dissolution. The relatively large apertures of unfilled shear fractures parallel to the orientation of SHmax are associated with the small effective normal stress exerted on fracture surfaces. Shear fractures effectively improve the overall permeability of Deng-4 Member carbonate reservoirs by connecting relatively isolated pores but have only minor impacts on reservoir porosity. The development degree and effectiveness of fractures together determine the contribution of fractures to reservoir permeability. In the Gaoshiti-Moxi area, shear fractures in the NWW-SEE and nearly E-W strikes provide the major flow pathways and contribute the most of permeability of the tight carbonate reservoirs in Deng-4 Member. These results provide insights for deeper understanding of the impact on reservoir quality of natural fractures in tight carbonates, and are significant for the evaluation of high-quality carbonate reservoirs in the Sichuan Basin.

The brittleness of shale reservoirs is of great significance for shale gas development. The brittleness index is the most intuitive parameter reflecting reservoir brittleness. The key exploration and development strata of shale gas in Pengshui area of southeastern Chongqing are Wufeng Formation of Upper Ordovician and Longmaxi Formation of Lower Silurian, and the high-quality shale reservoir is Wufeng–Long 1 section. The results show that the high brittleness grade of shale corresponds to low Poisson's ratio and high Young's modulus, but the relative distribution index of brittle minerals also affects brittleness. Through the analysis and calculation of brittle minerals and clay minerals in reservoir, the brittle index is calculated using rock physical parameters and mineral composition, and the advantages and disadvantages of the two are compared. Then a new formula for calculating brittleness index is obtained by combining rock physical parameters and mineral composition. Finally, the brittleness of high-quality shale reservoir in southeast of Chongqing area is evaluated comprehensively. Compared with the measured brittleness, the new formula has good effect. The average brittleness index of the Wufeng–Long 1 is more than 70% in Nanchuan area, China. The lateral distribution is stable and the fracturing conditions are good.

The marine shale of the Upper Ordovician Wufeng Formation–Lower Silurian Longmaxi Formation is the main source rock and the target of shale gas exploration in the southern Sichuan Basin. The maturity of organic matter (OM) is a vital indicator for source rock evaluation. Due to the lack of vitrinite, the organic matter maturity of the Wufeng–Longmaxi Formations in the southern Sichuan Basin is difficult to accurately evaluate. In total, 33 core samples of the Wufeng–Longmaxi Formations in the southern Sichuan Basin were selected to observe the optical characteristics of solid bitumen and graptolites and measure their random reflectance. Simultaneously, Raman spectroscopic parameters of kerogen were also used to quantitatively analyze the change in maturity. By using Raman spectroscopic parameters as mediators, conversion equations between graptolite random reflectance (GRor) and equivalent vitrinite reflectance (EqVRo) were established. Taking the calculation results of EqVRo as constraints, the tectono-thermal evolution history of Wufeng–Longmaxi Shale in the southern Sichuan Basin is constructed through basin modelling. The results show that the maturity of Wufeng–Longmaxi Shale in the western Changning, Luzhou-western Chongqing, eastern Changning and Weiyuan areas decreases successively. The EqVRo falls in the ranges of 3.61%~3.91%, 2.92%~3.57%, 3.08%~3.25%, 2.41%~3.12%, and the average EqVRo is 3.73%, 3.30%, 3.18% and 2.80%, respectively. Thermal evolution in western Changning was controlled by the thermal effect of the Emeishan mantle plume and paleo-burial depth, while the thermal evolution of other areas was mainly controlled by paleo-burial depth. This study provides a reliable parameter for the evaluation of thermal maturity and makes a more accurate calibration of the maturity of the Wufeng–Longmaxi Formations in the southern Sichuan Basin; it also expounds the factors for the differences in thermal evolution in different parts of the area.

针对高石梯地区(灯影组四段)灯四段储层地震响应特征不明及前期识别的"宽波谷+'亮点'"地震模式适用性问题,在研究区背景地层地震反射特征分析的基础上,研究了储层地震响应差异的影响因素并建立了相应的正演模型,然后结合实际资料总结了灯四段储层的地震识别模式,最后分析了平面地震振幅属性所表征的储层特征.结果 表明,储层性质的相似性是储层地震响应多解性的重要来源;储层组合特征是储层地震响应差异性的成因依据;灯四段顶部储层地震响应主要为震顶波峰减弱或下拉,灯四2储层可通过上亚段中部"亮点"与底部波峰特征进行识别,灯四1储层主要识别依据为单独珠状反射;通过实际地震响应特征建立起了高石梯地区灯四段储层的5种地震成因识别模式,高石1井区中均方根振幅属性与储层厚度具有一定的对应关系,准确提取该属性能够为研究区储层的有效预测提供参考依据.

Shale in the Wufeng Formation of the upper Ordovician and Longmaxi Formation of lower Silurian in the Sichuan Basin and its surrounding area is widespread. Shale gas resources are abundant. Shale gas in the Wufeng Formation and the Longmaxi Formation in the basin has been a major breakthrough. The basin margin transition zone in southeastern Chongqing is in an intense tectonic activity area, which is more complicated and special than the stable stratum in the basin. Therefore, it is necessary to put forward higher requirements for preservation conditions and enrichment pattern evaluation of shale gas. Therefore, in view of the complicated structural pattern of the basin margin transition zone in southeastern Chongqing, the preservation conditions and reservoir forming patterns are analyzed through structural evolution, uplift and denudation, fault development, structural styles, roof and floor conditions, and formation pressure. The results show that the main reason for the formation of normal pressure is the late uplift, denudation and fault development. The pressure coefficient from the basin to the outer layer is changed from overpressure to normal pressure, and structural transformation forms the preservation form of shale gas with narrow and steep residual anticline, wide residual syncline and residual slope. The preservation condition evaluation of normal shale gas should be based on structural factors such as structural evolution, structural style, uplift and denudation degree and fault development degree, with formation pressure coefficient as reference condition, combined with material basic conditions such as roof and floor conditions and formation thickness. The findings of this study can help for better understanding of the "sweet spot" prediction of normal pressure shale gas in complex structural area.

针对巴西盐下湖相碳酸盐岩储层物性非均质性强、岩性对储层物性控制弱的难题,采用小样本统计学习性能较强的支持向量机(support vector machine,SVM)解决储层物性评价问题.SVM不仅可以从复杂的测井信息中挖掘出储层物性信息,还可以从测井曲线中挖掘出岩性信息,解决因样本少而难以分岩性进行物性评价的问题.以实测孔隙度作为训练数据的标签,并以其对应深度的测井曲线作为训练数据,挑选出多条对储层物性敏感的特征曲线,采用SVM方法实现井点孔隙度和渗透率的准确预测.评价结果表明,与BP神经网络方法对比,SVM方法预测效果更佳,更适合样本点较少、处理复杂的非线性问题.