Reservoir pressure is critical for evaluating shale gas preservation and exploration potential in structurally complex regions. Along the southeastern margin of the Sichuan Basin, intense tectonic deformation may have contributed to pressure release and affected shale gas preservation. However, how different calcite vein types constrain stage-specific reservoir pressure evolution remains poorly understood remains poorly constrained. In this study, calcite veins within the Paleozoic Wufeng–Longmaxi Formation shales were investigated using integrated petrographic observations, geochemical analyses, fluid inclusion microthermometry, Raman spectroscopy, and burial–thermal history modeling. Three types of calcite veins were observed within the shale: bedding-parallel, broken, and high-angle veins. Geochemical indicators suggest a shift from relatively stable shale-reservoir fluids to increasing external-fluid input during fracture development. Bedding-parallel calcite veins are interpreted to have formed during early burial, probably in response to overpressure associated with hydrocarbon generation, with precipitation inferred at ca. 190 to 165 Ma and reservoir pressures of 56.2 to 76.7 MPa. In contrast, broken and high-angle calcite veins likely record uplift-related fracture reactivation and syn-tectonic fracture opening under tectonic compression, with precipitation inferred at ca. 130 to 97 Ma and reservoir pressure declining from 106.4 to 61.2 MPa. These results suggest that shale gas reservoirs in the structurally complex southeastern Sichuan Basin likely underwent a transition from overpressure to near-hydrostatic conditions during the late Yanshanian. These findings provide stage-specific constraints on reservoir pressure evolution and offer insights into shale gas preservation in structurally complex settings.

Deep shale gas has become a strategic alternative resource in China’s oil and gas energy portfolio. The core scientific challenges in the exploration and development of marine deep shale gas in the Sichuan Basin primarily include the formation mechanisms of shale reservoirs, the enrichment patterns of gas reservoirs, and multiphase/multiphysics-coupled seepage mechanisms. This study integrates experimental analysis with theoretical modeling, achieving the following breakthroughs. A CO 2 –N 2 —high-pressure mercury intrusion joint characterization technique based on density functional theory (DFT) was developed, enabling accurate quantitative characterization of full-aperture pores in deep shale. Nuclear magnetic resonance (NMR) T 2 spectrum distribution technology was used to quantitatively analyze organic pores, inorganic pores, and microfractures in shale. Quantitative pore–fracture characterization revealed that the coupled effects of quartz compression–resistant pore preservation and reservoir fluid overpressure are key to the high porosity of marine deep shale in the Sichuan Basin. A novel paleotherm/pressure evaluation method was innovatively developed using laser Raman spectroscopy, fluid inclusion homogenization temperature measurements, and Sm‒Nd dating, enhancing the precision of paleothermobaric reconstruction during different uplift stages. Through laboratory experiments on shale adsorption‒desorption and molecular dynamics simulations, a new method for evaluating gas content was established. Integrating geological characteristics, the adsorption‒desorption behavior and main controlling factors of enrichment and accumulation in deep shale were clarified, confirming that free gas is dominant in deep shale gas reservoirs. By comprehensively considering adsorption/desorption, stress sensitivity, microscale flow, surface diffusion, and fracturing fluid effects, a multiphase/multimechanism seepage model was established, enabling dynamic predictions of gas‒water two-phase transient productivity in horizontal wells, characterization of complex fracture network distributions, and description of fracture parameter evolution during production. These technologies have played a crucial role in facilitating breakthroughs in the exploration of deep marine shale gas.

Quartz, as a pivotal constituent of shale, has garnered considerable attention in research. Nevertheless, prior studies on quartz in shale have concentrated on its influence on organic matter accumulation, pore development, and physical properties. The crystal morphology of quartz and its implications for shale reservoir performance have been largely overlooked. This study utilizes the Longmaxi (LMX) shale in the Sichuan Basin, China, as an example to conduct this work. We used X-ray powder diffraction, polarizing microscopy, scanning electron microscopy, and cathodoluminescence testing, characterizing the crystallinity and characteristics of quartz, revealing the influence of quartz crystallinity on shale reservoirs. The results indicate that the quartz crystallinity index (QCI) of the LMX shale ranges from 2.81 to 8.09, and a significant correlation between the QCI and the sources of quartz is observed. Shale samples with lower QCI values tend to exhibit a higher content of biogenic quartz, whereas the content of clay-transformed quartz and/or terrigenous detrital quartz increases. Furthermore, the pore structure parameters of shale exhibit synergistic variations with QCI, especially for shale with low crystallinity, despite showcasing differences for pores with different pore sizes. Notably, QCI exhibits the strongest negative correlation with micropores, followed by mesopores, while this correlation is less apparent in macropores. The influence of QCI on pore development is primarily ascribed to its synergistic interaction with organic matter enrichment and the constraints imposed on the development and preservation of organic-matter-hosted pores. Under the well-preserved geological conditions of the LMX shale reservoirs, a definite correlation exists between the QCI value and shale gas content/production. This correlation signifies that QCI could serve as a potential indicator for assessing shale reservoir quality, complementing conventional parameters, such as the contents of total organic carbon and quartz.

Sedimentary environment can be restored qualitatively or semi-qualitatively by using elements or element combinations that are sensitive to paleoenvironment conditions. By measuring the major elements, trace elements and rare earth elements of 23 shale samples collected from coring wells in the Central Nanpanjiang Basin, we discussed the paleoenvironment conditions, including paleo-water depth, redox conditions, paleoclimate and provenance. La and Co contents indicate that the paleo-water depth in the Central Nanpanjiang Basin gradually deepened during the Late Permian. The ratios of U/Th, U au , V/Cr, Ni/Co and V/Sc suggest that the Central Nanpanjiang Basin was in an oxic condition in the Late Permian, which was stable during the Permian Longtan and Dalong depositional periods. C-value (Climate index value) and binary diagrams of Sr/Cu and Ga/Rb show that the Central Nanpanjiang Basin was characterized by a warm and arid climate during the depositional of the Permian Longtan Formation, a warm and humid climate in the lower part of the Dalong Formation, and a warm and arid climate again in the upper part of the Dalong Formation. The chemical index of alteration (CIA), plagioclase index of alteration (PIA), index of chemical variability (ICV), and Th/U and K/Rb values can indicate the geological tectonic settings of source regions. From the Longtan period to the Dalong period, the small CIA amplitude and relatively stable ICV indicate that chemical weathering in the source area was constantly slighty weak. However, Th/U increased significantly but PIA increased slightly in the lower Dalong Formation, indicating an obvious climate change in the early deposition of the Dalong Formation. In addition, the geochemical discrimination calculation and plots show that the provenance of the studied shales was related to felsic volcanic rocks and the tectonic settings of the Upper Permian shale source areas in the Central Nanpanjiang Basin were mainly oceanic island arc and continental arc.

The deeply-buried (>3500 m) Longmaxi Formation (LMX) shale in the southern Sichuan Basin, China, has become an attractive target for shale gas exploration owing to its huge resource potential. Exploration shows that the deep shale has a wide range of gas-in-place (GIP) contents, with variable gas yields, but the reason remains unclear, especially the impact of pore water on gas-bearing property lacks systematic research. In the present study, a suite of deep LMX shale samples was collected from the well FB1 in the Luzhou area of the southern Sichuan Basin, and techniques such as the pore water content measurements, low-pressure gas (CO2 and N2) adsorption and high-pressure methane adsorption experiments of the moist and dry samples were employed to investigate the distribution of water in the nanopores and its effects on the gas-bearing property. The results show that the deep shale is characterized by a high water content, with a high water saturation (average up to 69.80%), and the water occurs in both the inorganic and organic pores. The water reduces the effective specific surface area and pore volume of the shale averagely by 79.01% and 22.56%. Consequently, the water results in the decrease of methane adsorption capacity averagely by 45.13%. The GIP content models of two typical shale samples indicate that their total gas content is < 3 m3/t under the actual conditions, without development potential, and it will increase significantly to >3 m3/t with decreasing water saturation to <40–50%, especially under overpressure conditions. The gas-bearing property of deep LMX shale reservoirs in the complex faulted zones or structural-complex zones would mainly depend on the pore water content except for the properties of shale itself (e.g., maturity, TOC content, mineral composition, porosity and pore structure).

The lower Cambrian and lower Silurian shale reservoirs of southern China display signi ficant differences in pore characteristics that may re flect the varying effects of silica diagenesis. The lower Cambrian and lower Silurian mudstone samples from the middle -upper Yangtze platform were analyzed to elucidate silica diagenetic modi fications, including their in fluences on pore evolution. Quartz of the studied mudstone samples includes detrital quartz, overgrowths, siliceous skeletal fragments, microquartz aggregates, silica nanospheres, and matrix-dispersed microquartz. Much of the authigenic silica precipitated in association with diagenetic alteration of the studied deposits appears to have been derived from dissolution of siliceous skeletal fragments and the smectite -illite reaction. A paucity of siliceous organisms populating the early Cambrian ocean gave rise to more complicated silica diagenetic pathways during alteration. Silica precipitation from silica-rich seawater/pore water and silica replacement by carbonate/carbonate- fluorapatite may have supplemented diagenetic modi fication of lower Cambrian mudstone. The species types of organisms that contributed skeletal grains to the sediments and the amount of precipitated authigenic quartz appear to have impacted organic pore evolution. The abundance of early Cambrian benthic siliceous sponge spicules appears to have muted formation of rigid microquartz aggregates and silica nanospheres that would have shielded organic pores. In contrast, the early Silurian bloom of planktonic radiolarians was associated with accumulation of organic-rich siliceous mudstone and the formation of abundant microquartz aggregates and silica nanospheres that shielded organic pores during burial. In summary, the amount and type of diagenetic quartz influenced pore characteristics of lower Cambrian and lower Silurian shale reservoir rocks of southern China

CO 2 and N 2 gas adsorption are used to study the pore structure characteristics of WufengLongmaxi ultra-deep shales from Eastern Sichuan Basin.A group of Wufeng-Longmaxi mid-shallow shales and deep shales from peripheral area are selected as parallel samples in order to study the effect of burial depth on pore structure characteristics of shales.The results show that the pore types in the Wufeng-Longmaxi ultra-deep shales are mainly organic pores.The morphology of pores is mainly ink bottle pore（fine-neck and wide-body pore）.Mesopores and micropores account for about 90%of the total pore volume.The pore diameter of micropores is distributed around 0.35,0.50and 0.79nm,and the pore diameter of non-microporous pores is mainly distributed in the range of 2.00-10.00nm.The pore structure of ultra-deep shales is mainly controlled by its TOC mass fraction,and quartz also plays a certain role in controlling the formation and preservation of pores.Clay minerals are easy to be influenced by compaction due to the nature of strong ductility,which is not conducive to the development and preservation of intergranular pores.The mesopore volume or micropore volume of ultra-deep shales is significantly lower than that of mid-shallow shales and deep shales,indicating that burial depth will also affect the pore structure characteristics of ultra-deep shales.Under ultra-deep burial conditions,mesopores and larger micropores are subjected to strong compaction and evolve into micropores with smaller pore diameter,resulting in the overall pore diameter reduction of ultra-deep shales.This result provides guidance for the exploration and development of ultra-deep shale gas in Sichuan Basin.

Recently, shale gas exploration of the Wufeng-Longmaxi formations (WF-LMX) in the Sichuan Basin has gradually stepped into deep to ultra-deep layers, but the pore types and characteristics of ultra-deep shale still remain unclear. In this study, the WF-LMX ultra-deep organic-rich shale samples in the Eastern Sichuan Basin were collected, and the types and development characteristics of shale pores were investigated by using high-resolution scanning electron microscopy (SEM). Our results showed that the pores of the WF-LMX ultra-deep shale reservoirs mainly included organic pores, mineral matrix pores (interparticle pores and intraparticle pores), and micro-fractures, which were dominated by organic pores, displaying oval, slit, and irregular shapes and a diameter of mainly 5–45 nm. Organic pores were poorly developed in primary organic matter (e.g., graptolite and radiolarian), while they were well developed in solid bitumen, being the most important nanopore type in shale. The pore development of ultra-deep shale was mainly controlled by the contents of organic matter and brittle minerals. Higher contents of organic matter and quartz are conducive to the development and preservation of organic pores, which are also favorable for ultra-deep shale gas exploration.

To clarify the micropore structure and fractal characteristics of deep overpressured organic-rich shale in Wufeng and Longmaxi Formations in Southeast Sichuan basin,in this work it takes the organic-rich shales in Wufeng and Longmaxi Formations from four typical wells in the Dingshan and Dongxi areas as the research object.After ascertaining the mineralogical and geochemical characteristics of shale rocks,high-resolution scanning electron microscope,low-temperature gas （N 2 ,CO 2 ）adsorption,and mercury intrusion porosimetry experiments are used to qualitatively and quantitatively characterize the micropore structure of organic shale from the Wufeng and Longmaxi Formations.Based on gas （CO 2 and N 2 ） adsorption,mercury intrusion porosimetry and fractal theory,the fractal dimensions of pores in shale are calculated,and the internal relations between pore structure parameters,mineral composition,total organic carbon （TOC） content and fractal dimension of shale in different lithofacies are discussed.Results show that organic pores,inorganic pores （intergranular pores and intragranular pores） and microfractures are widely developed in these shale samples from Wufeng and Longmaxi Formations in the Dingshan and Dongxi areas.The pore morphology is dominated by wedge-shaped,slit-shaped or some parallel plate pores.The pore size distribution is multimodal.Mesoporeis the main contributor to the total pore volume （accounting for approximately 59%）,and micropores are the minor contributor to the total pore volume （accounting for approximately 35%）.The contribution of macropore to the total pore volume is relatively small.Influenced by the differences of rock composition,TOC content and diagenesis,the pores of different shale lithofacies show various evolution characteristics,resulting in strong heterogeneity and complex pore structure.The pores of the Wufeng-Longmaxi shale in the study area have obvious multi-scale fractal characteristics,and the pore fractal dimension characteristics between shale lithofacies at different scales are different,reflecting the extremely strong heterogeneous characteristics.Among them,the micropore fractal dimension D 1 and mesopore fractal dimension D 2 of siliceous shale are the largest,developing a more complex micropore and mesopore pore structure network,which can provide a large number of gas adsorption sites and storage space.In contrast,silicon-rich argillaceous shale has the largest macropore fractal dimension D 3 ,indicating that the macropore pore structure is relatively more complex,which can provide more pore space and facilitate the storage of free shale gas.

The Jurassic Dongyuemiao Member is the most promising target for lacustrine shale gas exploration in Sichuan Basin. By integrating SEM, NMR, LTNA, and MICP experiments, and other basic measurements, the nanoscale pore category and structure and the corresponding controlling factors of Dongyuemiao lacustrine shale in Eastern Sichuan Basin are studied. The results denote that organic pores comprise primary pores within plant debris and secondary pores within bitumen. Inorganic pores are composed of intraparticle pores within calcite particles, intercrystalline pores between pyrite crystals, and interparticle pores between different minerals. The 4th Section lacustrine shale of Dongyuemiao Member has the best pore structure, exhibiting high organic pore proportion, large amounts of gas adsorption, and parallel plate-shaped pore morphology. Micropores (<2 nm) are the main contributors of the pore volume and surface area of Dongyuemiao lacustrine shale. Moreover, the enrichment of organic matter positively affects the formation of micropores and has no influence on the mesopore–macropore (>2 nm). Quartz does not significantly affect the nanoscale pore formation. The intraparticle pores within calcite particles constitute part of mesopore–macropore but not micropores. Clay minerals are conducive to the formation of micropores but play a negative role in the formation of mesopore–macropore.

Lacustrine shale oil has the potential to lead the development of China's oil and gas industry. By integrating scanning electron microscopy, low-temperature CO2 and N2 adsorption, high-pressure mercury intrusion, and nuclear magnetic resonance with centrifugation at different speeds, the pore system and pore fluid distribution of Da’anzhai Member lacustrine shale in the Sichuan Basin are studied. The results show that: (1) The reservoir space is mainly inorganic pores and micro-fractures. Nano-micron scale pores are commonly found and widely distributed in the Da’anzhai shale with multiple peaks of 28 nm, 200 nm, 900 nm, and 3.5 µm. The total pore volume ranges from 0.00849 to 0.02808 cm³/g, and the pores ranging from 100 nm to 1000 nm are the main contributors to total pore volume. (2) Pore fluid can be divided into movable oil, bound oil, and adsorption oil. The proportion of movable oil, bound oil, and adsorbed oil is 21.4%, 12.4%, and 66.2% in Da’anzhai shale, respectively. Movable oil mainly occurs in pores larger than 350 nm, bound oil is 30–350 nm, while adsorbed oil mainly exists in pores below 30 nm. (3) The higher the total organic carbon content and clay minerals content, the smaller the pore size, resulting in the low content of movable oil. The higher the content of brittle minerals such as quartz, the better the development of intergranular pores and microfractures, and the higher the content of movable oil. Through the grading evaluation of shale pore structure and pore fluid, it is conducive to guide the exploration and development of Da’anzhai shale oil, which has important theoretical and practical significance.

Following the discovery of the Fuling shale gas field,shale gas exploration in the Sichuan Basin has expanded into the structurally complex region on its southeastern margin,where the Qijiang shale gas field has benn discovered.The findings achieved in the study are as follows.(1)The Qijiang shale gas field is generally similar to the Fuling shale gas field in terms of geological features,as shown with high total organic carbon(TOC)content(average:2.62%),high porosity(average:4.53%),and high gas content(average:5.43 m3/t).It is a typical self-sourced dry gas reservoir of continuity.Furthermore,the Qijiang shale gas field exhibits complex surface and subsurface conditions,including a large burial depth range involving moderately deep to deep layers with a medium depth of 3 354 m,low geothermal gradients(average:2.99℃/100 m),and extensive formation pressure coefficient in a range of 0.98 to 1.98(average:1.50)spanning normal to ultra-high pressure.(2)A shale gas enrichment model for basin-margin nose-like faulted anticlines in the structurally complex region is established featuring enrichment at deep burial areas as controlled by major fault zone,and this specifies that the shale gas enrichment in the anticlines,the critical features of shale gas sweet spots encompass high-quality shale,high fluid pressure,well-developed microfractures,and low in-situ stress.(3)Technologies applicable to deep shale gas reservoirs are developed,including sweet spot prediction technology and volume fracturing to form intricate fracture networks,providing a firm guarantee for high,stable gas flow in the Qijiang shale gas field.In November 2022,estimated shale gas in-place of 1 459.68×108 m3 from the Wufeng-Longmaxi formations in the Dingshan block was booked for the first time.

With the urgent need to increase shale gas production and reserves, deep shale gas has gradually become an important target for further exploration in China. However, there is still a lack in systematic research on the quality of different lithofacies types of shales in deep shale gas reservoirs. The overmature shales have a common problem, that is, the organic matter (OM) quality could not be clearly characterized by using conventional organic geochemical indicators, hindering the process of fine shale gas exploration. In this study, the deep marine Longmaxi (LMX) shale samples in the Dingshan area, southeastern Sichuan Basin were selected as a study case to investigate their lithofacies types, sedimentary environment and organic matter accumulation (OMA) mechanism, and restore the original OM attributes including original organic carbon content (TOCo) and original hydrogen index (HIo) for the different shale types to identify the favorable lithofacies for shale gas enrichment. The results show that the LMX shale can be divided into five different lithofacies, such as the OM-rich siliceous (RS) shale, OM-rich mixed (RM) shale, OM-lean siliceous (LS) shale, OM-lean mixed (LM) shale and OM-lean argillaceous (LA) shale, with a gradually decrease of their TOC contents. The TOC content of the LMX shale has a positive synergy with the indicators of paleoproductivity and redox conditions. However, since the studied area is close to the underwater highland with a high oxygen content in the bottom water and a great input of terrigenous debris, the OMA mainly depends on the level of high paleoproductivity. The analysis of sedimentary environment indicates that the OM amount and quality in various lithofacies shales are different. The RS shale at the lower part of the LMX shale has a better OM quality and a greater TOCo, which result in the greater effective organic carbon (TOCe), gas production potential, and retained gas content. It is followed by the RM, LS, and LM shales. In contrast, the LA shale lacks material base for shale gas enrichment. Combined with the available data from other deep blocks in the southern Sichuan Basin, the original OM attributes of RS and RM shales are always better than those of LM, LS, and LA shales. For deep and ultra-deep Longmaxi shale gas exploration, the RS shale should be the first choice, and then the RM shale.

富有机质页岩中广泛发育的纳米孔隙是页岩气的重要储集空间.为了明确页岩有机质孔隙发育特征,以四川盆地东南部丁山地区下志留统龙马溪组页岩为研究对象,通过扫描电镜(SEM)、N2和CO2低压吸附实验,对龙马溪组页岩有机质面孔率进行统计,并对页岩中纳米孔隙结构特征进行表征.结果表明,总有机碳(TOC)含量是影响龙马溪组页岩纳米孔隙比表面积和孔容的主要因素.龙马溪组页岩有机质孔隙的比表面积和孔容均随TOC含量上升而增加,且在TOC值较高时超过无机孔隙的比表面积和孔容.孔径为2-10 nm的孔隙对龙马溪组页岩的总孔容贡献最大.焦沥青相比于其他有机质发育更多的介孔,焦沥青含量增多将导致页岩中介孔孔容显著增加,而排油效率可通过影响焦沥青含量间接导致页岩纳米孔隙发育差异,高排油效率会降低页岩介孔和总孔孔容.在龙马溪组页岩勘探开发过程中,应综合考虑TOC含量、排油效率及焦沥青含量对页岩气储集条件的影响.

Recently, deeply-buried shale (depth > 3500 m) has become an attractive target for shale gas exploration and development in China. Gas-in-place (GIP) is critical to shale gas evaluation, but the GIP content of deep shale and its controlling factors have rarely been investigated. To clarify this issue, an integrated investigation of deep gas shale (3740–3820 m depth) of the Lower Paleozoic Wufeng–Longmaxi Formations (WF–LMX) in the Dingshan area, Sichuan Basin had been carried out. Our results show that the GIP content of the studied WF–LMX shale in the Dingshan area ranges from 0.85 to 12.7 m 3/t, with an average of 3.5 m3/t. Various types of pores, including organic matter (OM) pore and inorganic pore, are widely developed in the deep shale, with total porosity of 2.2 to 7.3% (average = 4.5%). The OM pore and clay-hosted pore are the dominant pore types of siliceous shale and clay-rich shale, respectively. Authigenic quartz plays a critical role in the protection of organic pores in organic-rich shales from compaction. The TOC content controls the porosity of shale samples, which is the major factor controlling the GIP content of the deep shale. Clay minerals generally play a negative role in the GIP content. In the Sichuan Basin, the deep and ultra-deep WF–LMX shales display the relatively high porosity and GIP contents probably due to the widespread of organic pores and better preservation, revealing great potentials of deep and ultra-deep shale gas. From the perspective of rock mechanical properties, deep shale is the favorable exploration target in the Sichuan Basin at present. However, ultra-deep shale is also a potential exploration target although there remain great challenges.

The Upper Permian Linghao Formation marine shale and contemporaneous transitional shale are the most potential shale gas targets in the Nanpanjiang basin, which is characterized by considerable TOC content, wide distribution, and considerable shale thickness. On the basis of division in Linghao Formation, petrographic, mineralogical, and high-resolution geochemical analyses were integrated to reveal the sedimentary environment including paleoproductivity, paleoredox conditions, detrital influx, paleoclimate, and the paleosalinity. There are two organic-rich shale intervals in Linghao Formation, which are Ling 1 member and the lower Ling 3 member. The lower Ling 1 is dominated by deep-water shelf facies, which are characterized by high TOC value (0.93%–6.36%, avg. 2.43%), high detrital influx proxies (Zr, 746–1508 ppm, avg. 1093 ppm; Ti, 19278–128730 ppm, avg. 16091 ppm), relatively warm–humid paleoclimate condition (CIA*, 75.94-91.90, avg. 82.26), low paleosalinity proxies (Sr/Ba, 0.13-0.34, avg. 0.22), and high paleoproductivity (P/Al (10−2), 1.06-2.06, avg. 1.63; Mn/Ca (10−3), 27.37-291.69, avg. 128.07). Detrital influx including gravity flow plays a critical role in the enrichment of organic matter. The sedimentary environment of upper Ling 1 and lower Ling 3 is the same as that of lower Ling 1. Unlike lower Ling 1, these intervals are characterized by low detrital influx proxies, moderate weathering, and relatively high paleosalinity proxies. The volcanic ash of Emei volcanism and felsic volcanism in South China plays a critical role in the enrichment of organic matter in upper Ling 1 and lower Ling 3, respectively. The sedimentary models for Linghao Formation organic-rich shale can reveal factors controlling the enrichment of organic matter.

四川盆地侏罗系湖相页岩层系多、页岩油气资源十分丰富,有望成为中国页岩油气"提储增产"的重要接替领域.以四川盆地复兴地区侏罗系陆相页岩为研究对象,总结该区优质陆相页岩储层地质特征,提高对陆相页岩油气富集成藏的认识,提出适用于陆相页岩油气勘探开发的3项关键技术.研究结果表明:(1)早—中侏罗世,四川盆地复兴地区主要发育自流井组东岳庙段、大安寨段及凉高山组二段3套半深湖相优质页岩储层,总体具有中等TOC、中等孔隙度和高黏土矿物含量特征;(2)沉积相带控制陆相页岩储层的发育与分布,沉积环境和保存条件控制陆相页岩油气富集成藏,天然裂缝控制陆相页岩油气高产,热演化程度控制陆相页岩油气藏类型;(3)高分辨率"甜点"预测技术、水平井高效导向钻井技术及低脆性页岩储层体积压裂技术3项关键技术适用于陆相页岩油气勘探开发.分析认为,四川盆地复兴地区侏罗系陆相页岩油气潜力较好,在现有技术条件下具有很好的勘探开发前景.

目前五峰—龙马溪组黑色页岩中显微组分缺乏统一的分类方案,命名也较为混乱,给页岩气勘探与评价造成了困难.为此,采用全岩光片和有机地球化学(TOC、δ13Corg)分析等方法,对四川盆地五峰—龙马溪组黑色页岩中显微组分进行有效识别与特征总结,探讨其可能成因,并判断其有机质类型.研究结果表明:五峰—龙马溪组页岩中显微组分主要由海相镜质组、腐泥组、动物有机碎屑组和次生组组成.其中,海相镜质组由无结构镜质体组成,呈浑圆状或长条状,具有强的光反射能力,但分布并不广泛;腐泥组主要由无结构腐泥体组成,为藻类遭受热降解过程而形成的无结构且无固定形态的显微组分,在富有机质页岩中广泛分布;动物有机碎屑组主要包括笔石表皮体、几丁虫和放射虫有机碎屑体;次生组由次生沥青体组成,广泛分布在页岩基质孔隙中,呈无固定形状.五峰—龙马溪组页岩中主要发育腐泥组和次生组,其次为动物有机碎屑组和海相镜质组,其有机质类型以Ⅰ-Ⅱ1型干酪根为主,且腐泥组和次生组含量越高,有机质类型越好,其生烃潜力越大.