关键词: 陆丰X洼, 断裂活动强度, 断裂系统, 变形机制, 控洼-控源作用, 珠江口盆地

Abstract:  Based on 3D seismic data, the mechanism of fault deformation and its control on hydrocarbon accumulation in the Zhu Ⅰ depression of Pearl River Mouth basin are studied by means of the determination of fault activity period, dislocation-distance curve and balanced section, in order to clarify the migration characteristics and distribution law of hydrocarbon source rocks. The results show that the Lufeng X sag is a north-south superhalf graben controlled by the NE-NEE-NWW arc fault (F1), and the NE, NEE and EW trending secondary faults are developed in the depression. The study is divided into two sub-depressions, east and west, according to the segmentation characteristics of the main fracture and the fracture combination style. The main fault is active in multiple stages, and has undergone three stages of tectonic deformation: Rift-Ⅰ, Rift-Ⅱ and Rift-Ⅲ. Five fault systems, namely, long-term active fault, Early Wenchang-Enping active fault, Early Wenchang-Enping active fault, Late Wenchang-Enping active fault and Enping active fault, have been formed in the basin with different deformation characteristics. In terms of origin, the internal fault of Lufeng X sag is generally controlled by the NE-NEE-NWW-arc-shaped pre-thrust and transformation fault system of the basement. In the basin forming period, the west sub-depression has extensional deformation along the pre-existing NE-NEE trending fault, and the east sub-depression has tension-torsion deformation along the pre-existing NWW-trending strike-slip fault. In the deformation process, the west sub-depression has formed a reverse cutting fault due to the influence of section reconstruction. The east sub-depression forms a special structural pattern of “V” shape. The controlling subsidence faults all have the characteristics of segmented growth, controlling the migration of sedimentary centers from northwest to southeast and from the edge of the basin to the basin, and affecting the distribution of source rocks in the 3rd and 4th member of the Wenchang Formation.

Key words: Lufeng X sag, fault activity intensity, fault system, deformation mechanism, depression controlling-source controlling effect, Pearl River Mouth basin