关键词: 渤海湾盆地, 黄骅坳陷, 页岩型页岩油, 富集规律, 甜点评价, 有利区

Abstract: The exploration practice in recent years has proved that the retained shale oil is developed in the main source rock series in Member 2 of Kongdian Formation, Member 3 of Shahejie Formation and Member 1 of Shahejie Formation in the Paleogene of Huanghua depression, Bohai Bay Basin. However, in Huanghua depression, the expanded exploration and large-scale development of shale oil are restricted by unclear enrichment laws and favorable layers/areas of shale oil. Based on testing data of the Paleogene of Huanghua depression regarding coring, rock slice, well logging, oil test, source rock evaluation and comparative experiment of slippery water imbibition under atmospheric pressure, this paper systematically analyzes the source rocks, reservoir properties and preservation conditions of shale oil in Huanghua depression, and explores the enrichment modes of shale oil and the distribution laws of favorable areas in Huanghua depression. It is found through the research that the enrichment of the Paleogene shale-type shale oil in Huanghua depression is mainly controlled by the source material supply and source rock conditions such as moderate source material supply, moderate total organic carbon content (TOC content of 2%~6%), moderate organic matter type (dominated by Type I, followed by Type III), and moderate thermal evolution maturity (R_o of 0.7%~1.2%); suitable reservoir conditions such as high density of micro-nano laminae (up to 15 000 laminae/m), high proportion of micro-nano pores (average porosity of 4.5%), and high content of retained movable hydrocarbons (average S₁ of 4.2 mg/g); excellent preservation conditions such as ideal roof and floor sealing conditions (caprock thickness of 50~100 m), weak fault damage (distance between faults and the target layers of a horizontal well:450~550 m). The shale oil enrichment law in the Paleogene of Huanghua depression, which features "a matching between medium and high level" that involves good fabric facies, excellent cross-over effect and perfect match between source rock and reservoir has been established, as well as the enrichment modes of shale oil respectively based on three types of dominant fabric facies in the Paleogene (namely the millimeter-grade organic matter-felsic lamina, the centimeter-grade organic matter-siltstone lamina, and the millimeter-grade organic matter-carbonate lamina in Huanghua depression). Additionally, this paper puts forwards the selection criteria and quantitative evaluation method for favorable layers and areas of shale-type shale oil in the study area, and selects seven sets of Type I shale oil layers in the Paleogene of Huanghua depression as the preferred target layers for drilling. By now, under the guidance of relevant theoretical understandings and technical methods, breakthroughs have been made in the large-scale development of shale oil in Cangdong sag and the exploration of shale oil in Qikou sag. Specifically, the shale oil development demonstration area with a production capacity of 10×10⁴t/a has been preliminarily completed, and the economically viable development of shale oil at the oil price of 65 dollar/barrel has been achieved, which demonstrates the promising exploration and development prospects of continental shale oil in the faulted basins in eastern China.

Key words: Bohai Bay Basin, Huanghua depression, shale-type shale oil, enrichment regularity, sweet spot evaluation, favorable area