Shale oil is a kind of unconventional oil and gas, which is rich in reserves and has become an important strategic replacement resource for conventional oil and gas resources. However, the formation of shale oil resources is unique, and the characteristics of shale oil resources are different from those of conventional oil and gas resources. Shale oil is an unconventional oil resource occurring in reservoir rock series dominated by organic shale. Shale is not only the source rock of shale oil generation but also the reservoir that accumulates and preserves shale oil. Shale reservoirs formation is affected by many factors. This paper summarizes the research achievements on the main influencing factors of shale reservoirs formation at home and abroad in recent years, including (1) organic carbon content; (2) organic matter maturity; (3) organic matter type; (4) reservoir burial depth; (5) porosity; and (6) microscopic pore throat structure. This paper not only summarizes the previous research but also puts forward some suggestions for the future research direction. This paper has a certain reference value for a comprehensive understanding of shale reservoir formation.
Shale gas is a kind of unconventional natural gas that mainly exists both adsorbed and free gas in shale. Many types of rich organic matter mud shale formations are extensively developed in China. According to the geological background of rich organic matter shale development and shale gas geology conditions, shale in China is divided into south, north (north China-northeast), northwest, and Qinghai-Tibet. Among them, south area shale has large monolayer thickness with Paleozoic marine deposits mainly, high thermal evolution degree, strong late tectonic, rich shale gas resources; north area shale’s enrichment conditions are diversified, Paleozoic-Mesozoic-Cenozoic shale being completely developed with obvious rolling migration sedimentary characteristics, frequently high thin interbedding changes and obvious sedimentary phase belt partition; northwest type centers on Paleozoic and Mesozoic, the sedimentary type being complete with high organic matter abundance and relatively low thermal evolution degree of organic matter. Yangtze Paleozoic, Ordos Basin Mesozoic, and Bohai Bay Basin Cenozoic are favorable areas of shale gas exploration and development. It is of great significance to explore China’s shale gas resources and exploration and development practice, which can not only provide guidance for the development direction of China’s shale gas but also provide a useful reference for the development of shale gas industry in other countries and regions.
As an important unconventional resource, shale oil has attracted more and more attention and has become a hot spot for oil and gas exploration and development. Jiyang Depression of Bohai Bay Basin, located in Eastern China, is a shale oil development area worthy of great attention and is regarded as the focus of continental shale oil geophysical research and exploration and development practice. This paper summarizes the research results on the occurrence characteristics of shale oil reservoirs in Jiyang Depression in recent years. The main results are as follows: (1) on organic matter, the effective source rocks in Jiyang Depression are developed in salt-brackish water environment, and the third member of Shahejie Formation, the first member of Shahejie Formation, and the fourth member of Shahejie Formation are the main source rocks; (2) on lithofacies, organic-rich laminated lithofacies are the most favorable lithofacies for shale oil distribution in Jiyang Depression; (3) on pores, the micropores in Jiyang Depression are affected by mineral composition; (4) on the fractures, the existence of fractures in Jiyang Depression is mainly due to the high mineral content of carbonate rocks; and (5) on mineral composition, Jiyang Depression is generally rich in carbonate minerals and low detritus. The occurrence characteristics of reservoirs in Jiyang Depression are beneficial to the generation and preservation of shale oil.