Oblique extension of pre-existing structures and its control on oil accumulation in eastern Bohai Sea

• Published in: Petroleum exploration and development Vol. 46; no. 3; pp. 553 - 564
• Main Authors: REN, Jian, LYU, Dingyou, CHEN, Xingpeng, LIU, Pengbo, GUAN, Dayong, SU, Kai, ZHANG, Hongguo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2019; KeAi Communications Co., Ltd
• Subjects: Bohai Sea; extension component; Neogene; oblique extension; Paleogene; pre-existing faults; strike-slip component; Paleogene; Neogene; oblique extension; extension component; strike-slip component; pre-existing faults; Bohai Sea
• ISSN: 1876-3804; 1876-3804
• DOI: 10.1016/S1876-3804(19)60035-2

Based on 3D seismic data, the evolution mechanism and characteristics of faults were investigated to reveal the structural origin and its control on differential hydrocarbon accumulation through comprehensive analyses, including structure style analysis, fault activity analysis, analogue modelling and comparison among the wells. The complex fault system with differently trending faults resulted from strike-slip and rifting in Paleogene was partly activated, developed successively and stretched obliquely by the near-NS extensional stress field in Neogene. In the area little affected by pre-existing faults, new faults nearly perpendicular to the extension direction developed. The structural development in the study area was not caused by transpressional strike slip. Under the oblique extension effect of pre-existing faults, if the angle between the strike of pre-existing fault and the extensional direction is different, the strike-slip and extensional stresses are different in ratio. The larger the angle between the two is, the stronger the extensional component, the poorer the sealing ability of the fault, and the stronger the oil and gas migration capacity will be. Conversely, the smaller the angle between the two is, the stronger the strike-slip component, the better the sealing ability of the fault, and the poorer the oil and gas migration capacity will be. The accumulation condition analysis results considering the fault trend are in good agreement with the oil and gas shows in wells drilled in this area.