Geological characteristics of shale rock system and shale oil exploration breakthrough in a lacustrine basin: A case study from the Paleogene 1st sub-member of Kong 2 Member in Cangdong sag, Bohai Bay Basin, China

• 作者: CHEN Shiyue HAN Wenzhong JIN Fengming PU Xiugang SHI Zhannan XIAO Dunqing YANG Fei ZHANG Wei ZHAO Xianzheng ZHOU Lihong
• 来源期刊: 石油勘探与开发:英文版
• 学科: 地球科学
• 关键词: SHALE oil fine grained deposits horizontal well volume FRACTURING SHALE reservoir sweet spot PALEOGENE Kongdian Formation Cangdong SAG Bohai Bay Basin
• 年，卷（期）: 2018,（3）
• 页码范围: 377-388
• 页数: 12页
• 分类号: P618.13

摘要

A deep understanding of the basic geologic characteristics of the fine-grained shale layers in the Paleogene 1 st sub-member of Kong 2 Member(Ek21) in Cangdong sag, Bohai Bay Basin, is achieved through observation of 140 m continuous cores and systematic analysis of over 1 000 core samples from two wells. Basic geological conditions for shale oil accumulation are proposed based on the unconventional geological theory of oil and gas. The shale rock system mainly developed interbedded formation of felsic shale, calcareous and dolomitic shale and carbonates;high quality hydrocarbon source rock formed in the stable and closed environment is the material base for shale oil enrichment;intergranular pores in analcite, intercrystalline pores in dolomite and interlayer micro-fractures make tight carbonate, calcareous and dolomitic shale and felsic shale effective reservoirs, with brittle mineral content of more than 70%;high abundance laminated shale rock in the lower section of Ek21 is rich in shale oil, with a total thickness of 70 m, burial depth between 2 800 to 4 200 m, an average oil saturation of 50%, a sweet spot area of 260 km2 and predicted resources of over 5×108 t. Therefore, this area is a key replacement domain for oil exploration in the Kongdian Formation of the Cangdong sag. At present, the KN9 vertical well has a daily oil production of 29.6 t after fracturing with a 2 mm choke. A breakthrough of continental shale oil exploration in a lacustrine basin is expected to be achieved by volume fracturing in horizontal wells.