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白云凹陷是南海北部深水区已证实的地质条件最优越的富生烃凹陷,但前人对白云凹陷的研究在构造、沉积和成因机制上存在争议。近年来采集的高品质地震资料有效提高了白云凹陷地震反射界面识别、结构特征、沉积充填和构造演化研究的可靠性。选取白云凹陷为研究对象,将均匀岩石圈塑性变形的伸展拆离作用应用于白云凹陷的构造解析,在地震资料解释基础上,以拆离断层的厘定、理论模型与动力学分析为主要工作思路,进而阐明构造演化及其油气地质意义。白云凹陷11条控洼断层可厘定为拆离断层系,剖面上表现为多期正断层呈铲状,向下合并为一条大规模低角度正断层,晚期被差异抬升作用改造的特征;平面上具有波瓦状构造特征。拆离作用控制了白云凹陷的构造演化和沉积充填,白云凹陷经历拆离断陷期、断拗复合期和区域沉降期3个阶段构造演化;拆离作用及其之后的持续性区域沉降作用,使白云凹陷成为南海北部深水区面积最大、沉积最厚的凹陷;同时也控制了文昌组和恩平组主要烃源岩的分布和演化。
The Baiyun sag is the proven geocarbon-rich depression with proven geological conditions in the deepwater area of the northern South China Sea. However, previous studies on the Baiyun sag have been controversial on the tectonic, sedimentary and genetic mechanisms. The high-quality seismic data collected in recent years have effectively improved the reliability of seismic reflection interface identification, structural features, sedimentary filling and tectonic evolution research of Baiyun Sag. Based on the seismic data interpretation, taking the Baiyun sag as the research object, the extension and detachment effect of plastic deformation of uniform lithosphere was applied to the structural analysis of Baiyun sag. Based on the seismic data interpretation, taking the determination of the detachment fault, the theoretical model and the dynamic analysis as the main working ideas , And then elucidate the tectonic evolution and its petroleum geological significance. The 11 control depressions in Baiyun Sag can be determined as detachment faults. The multi-period normal faults are shovel-like in the section, which merge into a large-scale and low-angle normal fault and are characterized by differential uplift in the late stage. On the plane With wave-like structure features. The detachment control the tectonic evolution and sedimentary filling of Baiyun sag. The Baiyun sag underwent tectonic evolution in three stages of detachment and fault depression, fault-break complex period and regional subsidence; detachment and subsequent regional subsidence, So that the Baiyun sag became the largest and the thickest depression in the deepwater area in the northern South China Sea. Meanwhile, the distribution and evolution of major source rocks in Wenchang and Enping groups were also controlled.