Enrichment theory, exploration technology and prospects of shale oil in lacustrine facies zone of deep basin: a case study of the Paleogene in Huanghua depression, Bohai Bay Basin

Marine shale oil and gas in North America were commercially developed in the early 20th century, while the development of continental shale oil and gas in China is still in the exploratory stage, and most of them are distributed in lacustrine facies zone of deep basin. Based on summarizing the research progress of continental shale oil in China, focusing on the Paleogene shale oil in the Huanghua depression of Bohai Bay Basin as a typical example, and reviewing the exploration and development history of shale oil, this paper summarizes the theoretical achievements and technologies of shale oil obtained during exploration and development, analyzes the effectiveness and exploration potential of the current shale oil exploration and development, and makes clear the resource prospects of shale oil exploration and development in lacustrine facies zone of deep basin. The enrichment theory of "favorable tectonic facies and transcendence effect of retained hydrocarbon" reveals the structural characteristics of the dominant components of shale in lacustrine facies zone of deep basin as being high-density laminaed structure, high abundance organic matter, high felsic content and low clay content, clarifies the formation and enrichment regularity of shale oil, and establishes a shale oil enrichment model, laying a theoretical foundation and basis for the exploration and development of shale oil in lacustrine facies zone of deep basin. The calculation method of the mass oil content of residual movable resources in shale, the geological-seismic comprehensive evaluation method of the shale oil sweet spot, the fracturing technology of shale in lacustrine facies zone of deep basin, and the three-dimensional development technology of multiple sweet spots provide crucial technical supports for determining the quantity of shale oil resources, as well as deployment and efficient development of exploratory well. Benefiting from theoretical innovation and technological breakthroughs, the Member 2 of Kongdian Formation in the Cangdong sag, Huanghua depression has entered the stage of industrial development, with 46 drilled horizontal wells; the Member 3 of Shahejie Formation in the Qikou sag also has significant exploration results in the Qibei subsag. Horizontal wells such as Well QY10-1-1 and Well B56-1H have achieved breakthroughs in high and stable production. The shale oil in the Huanghua depression has great resource potential, production increase potential and cost reduction potential, which also indicates that China's shale oil resources have huge potential and broad prospects in lacustrine facies zone of deep basin. © 2021, Editorial Office of ACTA PETROLEI SINICA. All right reserved.