Crystalline dolomite is a common carbonate mineral in lacustrine fine-grained rocks, but it has a confusing origin that has been a focus of much debate in recent years. In our research, the fine-grained rocks rich in crystalline dolomite were sampled from the upper fourth member (UMbr 4) and lower third member (LMbr 3) of the Shahejie Formation in the Jiyang Depression, and analyzed by a variety of analytical techniques, including field emission scanning electron microscopy (FESEM), cathodoluminescence (CL), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), micro-area carbon, oxygen, strontium isotopes and electron probe analyses. The results show: (1) The crystalline dolomites in the lacustrine fine-grained rocks are primarily composed of ferroan-poor dolomite (FeO < 1%), type I ferroan dolomite (FeO approximate to 5%) and type II ferroan dolomite (FeO approximate to 16%); (2) The delta O-18 of ferroan-poor dolomites in mudstone is between -0.89 and 0.32 parts per thousand, the precipitation temperature is less than 60 degrees C, and their formation is related to the microbial action during the early diagenetic stage A, while the ferroan-poor dolomites in dolostone are primarily formed by the recrystallization of micritic dolomite; (3) The delta O-18 of type I ferroan dolomites ranges from -3.74 to -3.89 parts per thousand, the precipitation temperature ranges from 68.4 to 69.4 degrees C, and they are primarily formed by the microbial action and clay mineral transformation during the early diagenetic stage B; (4) The delta O-18 of type II ferroan dolomites is between -7.78 and -8.33 parts per thousand, the precipitation temperature is more than 90 degrees C, and their formation is related to the dissolution of early carbonate and clay mineral transformation during the middle diagenetic stage; (5) The origin mechanism of crystalline dolomite indicates the diagenetic evolution of fine-grained rocks and the migration path and storage of shale oil.

The effect of various depositional parameters including paleoclimate, paleosalinity and provenance, on the depositional mechanism of lacustrine shale is very important in reconstructing the depositional environment. The classification of shale lithofacies and the interpretation of shale depositional environment are key features used in shale oil and gas exploration and development activity. The lower 3(rd) member of the Eocene Shahejie Formation (Es-3(x) shale) was selected for this study, as one of the main prospective intervals for shale oil exploration and development in the intracratonic Bohai Bay Basin. Mineralogically, it is composed of quartz (avg. 9.6%), calcite (avg. 58.5%), dolomite (avg. 7%), pyrite (avg. 3.3%) and clay minerals (avg. 20%). An advanced methodology (thin-section petrography, total organic carbon and total organic sulfur contents analysis, X-ray diffraction (XRD), X-ray fluorescence (XRF), field-emission scanning electron microscopy (FE-SEM)) was adopted to establish shale lithofacies and to interpret the depositional environment in the lacustrine basin. Six different types of lithofacies were recognized, based on mineral composition, total organic carbon (TOC) content and sedimentary structures. Various inorganic geochemical proxies (Rb/Sr, Ca/(Ca + Fe), Ti/Al, Al/Ca, Al/Ti, Zr/Rb) have been used to interpret and screen variations in depositional environmental parameters during the deposition of the Es-3(x) shale. The experimental results indicate that the environment during the deposition of the Es-3(x) shale was warm and humid with heightened salinities, moderate to limited detrital input, higher paleohydrodynamic settings and strong oxygen deficient (reducing) conditions. A comprehensive depositional model of the lacustrine shale was developed. The interpretations deduced from this research work are expected to not only expand the knowledge of shale lithofacies classification for lacustrine fine-grained rocks, but can also offer a theoretical foundation for lacustrine shale oil exploration and development.

在总结国内外相关文献的基础上,对砂质碎屑流的相关概念、沉积动力学过程及沉积特征进行系统梳理,并对争议问题进行了讨论。砂质碎屑流是一种富砂质具塑性流变性质的宾汉塑性流体,代表一个从黏性至非黏性碎屑流连续系列,具有中—高碎屑浓度（体积浓度25%～95%）、较低的泥质含量（体积浓度可低至0. 5%）、湍流不发育。其沉积物以块状砂岩、含碎屑逆粒序砂岩沉积为代表,局部可见滑动剪切构造和液化漩涡构造。砂质碎屑流的形成多经历滑动→滑塌→砂质碎屑流→浊流的有序演化过程;滑水作用和基底剪切润湿作用是克服砂质碎屑流与基底剪切摩擦拖拽的重要机制,流体强度则是克服上覆环境水体混入稀释的重要原因;砂质碎屑流头部和边部优先固结沉积,进而控制流体整体沉降。砂质碎屑流是形成深水块状砂岩的主要原因之一,砂质碎屑流在相对低流体效率的深水重力流沉积环境广泛发育。

随着能源需求的增加,勘探开发技术的进步,页岩油气作为一种重要的非常规油气资源在近些年来受到越来越多的关注。在泥页岩“自生自储”的油气系统中,储层的发育受次生孔隙的影响,而有机—无机相互作用则影响了次生孔隙的发育。论文在对研究区泥页岩有机地球化学特征和有机酸含量特征分析的基础上,进行了有机酸生成实验,分析了有机酸生成的影响因素。探讨了自然演化剖面上有机质演化与主要无机矿物间的相互作用,并开展了酸溶热模拟实验,分析了不同温度、不同介质条件下泥页岩中离子释放、矿物组成和孔隙结构的变化特征。通过对自然演化剖面和生烃热模拟实验中的孔隙演化特征的综合分析,结合有机—无机相互作用对孔隙发育的影响,建立了东营凹陷泥页岩孔隙的演化模式。研究结果表明,研究区泥页岩有机质类型以I型和II型为主,矿物主要包括方解石、石英、长石和粘土矿物;有机酸类型主要为甲酸、乙酸、草酸和游离有机酸,有机酸的生成受温度、p H、Ro和TOC的影响,其中TOC是主要控制因素。研究区泥页岩在有机质演化过程中产生的有机酸与碳酸盐矿物、长石会发生强烈的溶蚀反应,而石英在酸性环境中的溶蚀作用较弱;方解石在有机质演化后期阶段以重结晶作用为主,对孔隙结构起破坏作用,同时方解石的存在还会抑制有机质生烃的进行;还原环境中黄铁矿的生成对有机质生烃有催化作用;在有机质生烃和有机酸溶蚀的共同作用下,粘土矿物与有机质以及碳酸盐矿物形成了有机质—粘土—碳酸盐复合体孔隙,此外,粘土矿物中的蒙脱石伊利石化可以促进有机质脱羧的进行;膏盐的存在不仅有利于富有机质烃源岩的形成,还通过自身的热导性对有机质演化产生影响。酸溶热模拟实验中,加入的碳酸盐、硫酸盐、氯化钠增强了有机酸溶蚀泥页岩时的离子释放浓度,其中,碳酸盐和氯化钠的促进效果较为明显,硫酸盐的促进作用较弱;加入碳酸盐的实验组孔隙比表面积和孔体积有明显的增大,对孔体积来说,碳酸盐主要是通过增多介孔的数量来增大孔体积,在高温时碳酸盐对孔体积的增大作用更加显著。自然演化剖面和生烃热模拟实验的结果显示,孔隙演化的过程可以划分为5个阶段。未成熟阶段,孔隙以粒间孔和粒内孔为主;低成熟阶段,在有机质生烃和有机酸溶蚀的作用下,有机质孔和粒内孔的数量开始增多;成熟阶段,有机质大量生烃,有机酸溶蚀作用增强,再加上粘土矿物的转化,致使孔隙度逐渐增大;高成熟阶段,孔隙度出现减小的趋势;过成熟阶段,粒内孔和粒间孔数量减少,有机质孔增长速度变慢,整个孔隙系统处于稳定状态。

Generally, researchers believe that authigenic quartz precipitates in acidic medium and authigenic albite precipitates in alkaline medium. However, the lacustrine carbonate-rich fine-grained sedimentary rocks in the upper fourth sub-member and the lower third sub-member (Es-4(s)-Es-3(x)) of the Shahejie Formation in the Jiyang Depression were observed and it was found that authigenic microcrystalline quartz and albite generally develop together. Moreover, authigenic quartz and albite also develop with microcrystalline Fe-rich dolomite and calcite in clay laminae, while in carbonate laminae, they primarily develop with recrystallized calcite. In this study, thin-section, cathodoluminescence, field-emission scanning electron microscopy (FESEM), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and inclusion analyses were conducted to study authigenic minerals. The results show that authigenic quartz and albite are characterized by rich Ge in mudstone, and the material components mainly originate from the transformation of clay minerals and the dissolution of terrigenous feldspar debris. In limestone, they are characterized by poor Ge, and the material components primarily originate from the transformation of clay minerals. The paragrowth and intergrowth of authigenic quartz and albite primarily depend on the degree of supersaturation of the corresponding ion concentration under high temperature, high or ultrahigh pressure. During the early diagenetic stage, authigenic quartz and albite initially formed in a weakly alkaline environment; however, on entering the middle diagenetic period, authigenic quartz, albite, and sparry calcite formed in a weakly acidic environment, and the formation rate reached its peak. Our results elucidate the migration direction and enrichment law of shale oil in calcareous fine-grained sedimentary rocks through the genetic mechanism of authigenic quartzs and albites. Shale oil is generated from organic matter in the clay lamina, following which it migrates, accumulates, and preserves to the adjacent sparry calcite lamina under the joint driving effect of organic matter hydrocarbon generation overpressure and clay mineral dehydration overpressure.

Eocene organic-rich shales in the Dongying Depression, Eastern China, are well preserved and ideal for examining stratigraphic controls on the variations of organic matter (OM). This study concerns the Eocene sedimentary succession in the Dongying Depression and recognizes a third-order sequence based on the stacking patterns of lithofacies, mineralogical changes, and geochemical proxies. The total organic carbon content, RockEval parameters S1 and S2 values, and the chloroform bitumen "A" content are low in the lowstand systems tracts, reaching their maxima within the transgressive systems tracts and gradually decreasing within the highstand systems tracts. The paleoclimate index and ratios of quartz/feldspar, Sr/Ca, TiO2/Al2O3, Cr/Al, Ni/V, Th/U, Zn/Al, and Ni/Al indicate that OM accumulation was influenced by primary productivity, sedimentation rate (SR), and redox conditions, which are intimately related to the sequence development under the influence of tectonics, climate, sediment supply, and relative lake-level fluctuations. The OM distribution is related to the sequence stratigraphy in three ways: (1) climate and relative lake-level fluctuations affected the primary productivity and OM production via algae blooms and terrestrial OM input; (2) relative lake-level fluctuations and sediment supply were influenced by tectonics and climate, causing a change in SR and OM deposition; and (3) relative lake-level fluctuations under different climatic conditions affected the development of anoxic bottomwater favoring OM preservation.

Complex mineral composition, multiple depositional processes, and strong reservoir heterogeneity cause the complexity and uniqueness of a lacustrine shale oil reservoir. Understanding the storage space development and hydrocarbon occurrence model should facilitate the analysis of the shale oil reservoir and hydrocarbon accu-mulation in lacustrine shales. In this study, the storage space development model for different lithofacies and the modes of hydrocarbon occurrence in different storage space were analyzed in the Es4s-Es3x shale in the Jiyang Sub-basin, East China, based on thin-section and field emission scanning electron microscopy (FE-SEM) obser-vations, X-ray diffraction (XRD) analysis, physical property testing, and geochemical analysis. Inorganic pores, particularly recrystallization intercrystalline pores in calcite, are the key matrix pores for lacustrine shale oil. However, the types and abundance of storage space are noticeably different in various lithofacies. The hydro-carbon occurrence is mainly manifested in three states: (A) free state in interlaminar fractures, structural frac-tures, and abnormal pressure fractures; (B) adsorbed state in organic pores, intercrystalline pores in pyrite, and floccule pores; and (C) free state in large pore spaces, including dissolution pores and recrystallization inter-crystalline pores, which can form a continuous hydrocarbon accumulation. The hydrocarbon generation po-tential and thermal maturity are closely associated with the lithofacies and mineral composition. The matching mechanisms of pore formation as well as hydrocarbon generation, migration, and accumulation are favorable. Among the various lithofacies, the organic-rich calcareous shale has abundant storage space, high porosity, total organic carbon content, and hydrocarbon potential, making it a "sweet spot" for shale oil exploration.

Y Pore types and pore structure parameters are the important factors affecting the storage capacity of a shale oil reservoir. Pore morphology and mineralogical composition of shales have diverse effects on the upgrading of various phases of shale oil. To interpret the formation and distribution of different pore types and their structure parameters in the lacustrine calcareous shale, a combination of polarizing microscopy, X-ray diffraction, total organic carbon (TOC), field-emission scanning electron microscopy, and low-pressure nitrogen adsorption experiments were conducted on the Es3x shale of the Eocene Shahejie Formation in the Zhanhua Depression. The interpretations regarding pore types, pore structure parameters, and pore size distribution indicate that the pore morphology and pore size distribution in the lacustrine shale are very complicated and demonstrate strong heterogenic behavior. Inorganic pores (interparticle pores, intraparticle pores, intercrystalline pores, dissolution pores, and microfractures) are the most commonly distributed pore types in the studied shale. However, organic matter pores are poorly developed due to the lower thermal maturity of the Es3x shale. The Brunauer-Emmett-Teller specific surface and pore volume range from 0.026 to 1.282 m(2)/g (average 0.697 m(2)/g) and 0.003 to 0.008 cm(3)/g (average 0.005 cm(3)/g), respectively. The shape of the pores varies from slit-like to narrow slit. Different minerals develop different types of pores with various sizes extending from micropores (<2 nm), mesopores (2-50 nm), to macropores (>50 nm). The relationship between mineral components and pore parameters indicates that the carbonate minerals act as the main contributors to the formation and distribution of different pore types in the studied shale. Pore volume and the pore specific surface area did not show a good relationship with mineral composition and TOC due to disordered pores, but pore size shows a good relationship with mineral composition and TOC of the Es3x shale. The whole pore system description showed that the mesopores and macropores are abundantly distributed and are the main contributors to the pore system in the Es3x shale. A comprehensive understanding of the formation mechanism and structural features of various sized pores in a variety of different minerals can provide a good tool for the exploration and development of shale oil reservoirs.

Algae-rich oil shales have great hydrocarbon potential, and the hydrocarbon generation processes of different quality oil shales are important for shale oil resource exploration. This study comparatively analyzed the hydrocarbon generation processes of the general- and fair-quality oil shales from the first member of the Qingshankou formation (K(2)qn(1)) and the first member of the Nenjiang formation (K(2)qn(1)), separately. Organic petrology and X-ray diffraction analyses revealed that the fair-quality oil shale contained more telalginite and lamalginite and had a lower clay mineral content than the general-quality oil shale. Thermal simulations revealed that the fair-quality oil shale underwent an earlier oil generation peak and exhibited higher oil yields than the general-quality oil shale, implying that the hydrocarbon generation processes were sequential. After a thermal maturity (Ro) of 1.05% was reached, the fair-quality oil shale generated plentiful hydrocarbons, whereby the contribution of illite content rapidly increased from the illite/smectite layer. Analysis suggested that fair-quality oil shales can generate large volumes of hydrocarbons and organic acids under the effect of temperature due to the presence of bulk telalginites, and these organic acids in turn promote the transformation of smectite into illite. This greatly increased the catalytic activity of smectite and thus the rate of hydrocarbon generation. Finally, it was determined that the synergistic effects of organic matter and clay minerals contributed to the rapid hydrocarbon generation of the fair-quality oil shale, implying that fair-quality oil shales that are rich in telalginites have value as sweet spot layers for early shale oil exploration. This is important for the development of shale oil resources.

Natural analcime, an aluminosilicate mineral with multiple genetic mechanisms, widely occurs in fine-grained sedimentary reservoirs rich in oil and gas. Researchers have discussed the source and formation mechanism of reservoirs and the influence of morphology formation, occurrence characteristics associated with minerals, geochemical data, and Si/Al ratio on reservoir properties. The occurrence location, particle size, automorphism, purity, and fracture development can indicate the source of analcime macroscopically. The correlation between the enrichment of associated minerals and the content of analcime indicates that the associated mineral assemblage or correlation provides a material source for the formation of analcime or effectively improves the formation environment. Geochemical data are often used to identify analcime related to primary magmatic crystallization and hydrothermal processes. The genetic source grouping scheme based on the Si/Al ratio, which is a traditional means to identify the source of analcime, has been widely used in the research on analcime. After more than 200 years of study, research has shown that analcime distributed in fine-grained sedimentary rocks was mainly formed by burial alteration of volcanic materials (V-type analcime), conversion of nontuffaceous materials (N-type analcime), hydrothermal deposition mineralization (H-type analcime), and precipitation directly from an alkaline lake or pore water (P-type analcime). Based on reservoir properties, analcime that formed before the organic acid release stage of source rocks can effectively improve the porosity through precipitation-dissolution mechanisms after the release of massive organic acid, whereas the cementation formed by the transition of the fluid from acid to alkaline during the intermediate diagenetic stage would reduce porosity to some extent.