关键词: 渤海湾盆地, 沧东凹陷, 断陷湖盆, 孔二段, 页岩油, 勘探突破, 效益开发

Abstract: The large-scale and benefit development of shale oil in the second member of Kongdian Formation (Kong 2 member) in Cangdong Sag in Huanghua Depression face multiple challenges, such as evaluation and optimal selection of main production layers of medium-low mature shale oil, stereoscopic development and production of multiple vertical sweet spots, optimal and fast drilling and completion of horizontal section with a length of 2000 m in complex fault blocks, high-efficiency volumetric fracturing of laminated shale reservoir and high-efficiency lifting of shale oil with high viscosity and high wax content. Go through four stages of shale oil exploration, i.e., research, breakthrough in horizontal wells and pilot test of production capacity evaluation, 60% of the horizontal wells in production have a single well EUR of less than 2.0×10⁴t, and the low single well oil rate has become a bottleneck problem restricting the benefit development of lacustrine shale oil. By comprehensively analyzing wireline logging, mud logging, fracturing parameters and production data of Kong 2 member shale oil in 47 production wells, the systematic research has been conducted on sweet spot evaluation and optimal selection of sealing box, well pattern deployment, geosteering while drilling, fracturing reconstruction, and production regime for the lacustrine shale oil in complex fault blocks, and three sweet spot layers (C1, C3 and C5) have been identified for benefit shale oil development in Guandong area, with an favorable area of 42-53.3 km² and the estimated Class Ⅰ resources of 1.54×10⁸t. The pilot test of benefit shale oil development has been conducted on two 10 m-level sweet spot layers (C1③ and C3⑧) in Kong 2 member on No.5 platform in Cangdong Sag, in which the drilling difficulty of long horizontal section by water-based drilling fluids in complex fault blocks has been solved, the high-efficiency fracturing technology for laminated shale oil has been innovated, and permeability improvement, swelling energization and viscosity reduction of miscible fluids have been achieved of the laminated shale reservoir, with the tested single well peak oil output of 39.6-122.3t. As of June 22, 2023, the five pilot wells had been put into production for 174-201 days, and the cumulative oil output was 3.34×10⁴t. The predicted cumulative oil output in the first year is 6.5×10⁴t, and the average EUR of a single well is 4.11×10⁴t, which indicate that the large-scale and benefit development mode of lacustrine shale oil has been established in complex fault blocks.