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Occurrence and mobility of shale oil are prerequisites for evaluating shale oil reserves and prioritizing exploration targets, particularly for heterogeneous lacustrine shales. The Qingshankou Formation in the Gulong Sag, Songliao Basin is a classic lacustrine pure shale reservoir that contains abundant shale oil resources. The predicted geological reserves of the shale are 1.268 × 109 t. In this study, field emission scanning electron microscope (FE-SEM), the modular automated processing system (MAPS), pyrolysis-gas chromatography (Py-GC), low-pressure nitrogen gas adsorption (LPNA), Soxhlet extraction, pyrolysis, and 2-D nuclear magnetic resonance (NMR) were integrated to describe the shale oil components, microscopic occurrence, mobility, and the effective pore size distribution. Meanwhile, the related controlling factors are discussed.The shale oil in the Qingshankou Fm exists dominantly in the matrix pores of the clay minerals, with small amounts distributed in the intergranular pores of terrigenous clastic grains, intercrystalline pores of pyrite, intragranular pores of ostracod shells, and micro-fractures. Shale oil is distributed in the pore spaces of variable sizes in different lithofacies. The clay mineral-laminated shales are characterized by the broadest range of pore size and largest volume of pore spaces with shale oil distribution, while the ostracod-laminated shales have limited pore spaces retaining oil. Furthermore, the proposed integrated analysis evaluates the shale oil molecules existing in two states: movable, and adsorbed oil, respectively. The result illustrates that movable oil takes up 30.6%–79.4% of the total residual oil. TOC, mineral composition, and pore structures of the shale joint together to control the states and mobility of the shale oil. TOC values are positively correlated with the quantities of shale oil regardless of the state of oil. The mineral components significantly impact the state of shale oil. Noticeable differences in the states of oil were observed following the changing types of minerals, possibly due to their difference in adsorption capacity and wettability. Clay minerals attract more adsorbed oil than movable oil. Felsic minerals generally decrease the occurrence of total and adsorbed oil. Carbonate plays a positive role in hydrocarbon retention of all the shale oil states. As for the pore structure, the average pore size exerts a critical impact on the total, movable, and adsorbed oil content. The total pore volume and specific surface area of shales play a principal role in controlling the total yields and amounts of adsorbed oil. This research improves the understanding of the occurrence characteristics and enrichment mechanisms of shale oil in terrestrial pure shales and provides a reference for locating favorable shale oil exploration areas. [ABSTRACT FROM AUTHOR]

Abstract: Based on the controlling of diagenesis and diagenetic facies on reservoir development, this article discusses the formation, classification, and evaluation of diagenetic facies and its application and significance in petroleum exploration. For constructive diagenetic facies such as clastic rock, carbonate rock, and igneous rock, eight kinds of genetic mechanisms are developed, including dissolution of organic acid, dolomitization, and so on. Nine constructive diagenetic facies and seven destructive diagenetic facies are classified. A naming scheme for diagenetic facies is proposed reflecting lithology, diagenesis, porosity, and permeability, that is, “porosity and permeability level + rock type + diagenesis type”. Diagenetic facies are evaluated synthetically and quantitatively on the basis of sedimentary facies, log facies, seismic facies, rock cores, and thin sections, and “four steps” and “superposition of three charts” are put forward as the methods of evaluation and mapping. Favored reservoirs, “sweet spots”, and lithostratigraphic traps can be predicted according to the distribution of different types of diagenetic facies. The development of the study on diagenetic facies is also discussed in the article. [Copyright &y& Elsevier]

Abstract: Volcanic hydrocarbon exploration in China has experienced three phases: accidental discovery, local prospecting, and all-round exploration. There are mainly Carboniferous-Permian, Jurassic-Cretaceous, Paleogene-Neogene volcanic rocks and lava, pyroclastics, and karst reservoirs in the oil- and gas-bearing basins in China. Volcanic rocks cannot generate organic hydrocarbons, and the combination of volcanic rocks, source rocks, and seals are the key controlling factor of the primary lava plays. The near-source play is most favorable for hydrocarbon accumulation. Distribution of oil and gas is controlled predominantly by the hydrocarbon generating center. The play requires communication with faults or unconformities. Near-source plays are in the faulted basins in eastern China. Structural-lithologic hydrocarbon reservoirs are formed in the higher place of faults and lithologic hydrocarbon reservoirs are formed on the slope. Two types of plays are developed in central and western China. The near-source play is most favorable for the formation of large stratigraphic hydrocarbon reservoirs. [Copyright &y& Elsevier]