珠江口盆地文昌A凹陷西南部断裂转换带特征及其控藏作用

Characteristics of fault transfer zone in southwest Wenchang A sag, Pearl River Mouth basin and its role in hydrocarbon accumulation

伸展盆地中发育的断裂转换带对油气成藏具有非常重要的控制作用。珠江口盆地文昌A凹陷西南部发育斜向伸展背景下的大型断裂转换带,通过精细地震解释对断裂转换带开展构造特征研究,并进行成藏条件解剖。结果表明,文昌A凹陷大型断裂转换带主要受控于珠三南断裂带文昌A凹南段和6号断裂两条主干断裂,断裂转换带内部由北、中、南三个断裂带组成。其构造演化经历了古新世—始新世(神狐—文昌期)张裂、渐新世—早中新世(珠海—珠江期)右旋叠覆走滑、中中新世至今走滑作用增强转换带定型3个阶段。断裂转换带不仅控制了圈闭的发育,同时也对烃源岩、沉积体系及油气运聚有一定的影响。结合区域“内气外油、下气上油”的油气富集规律,指导了断裂转换带内部获得珠江口盆地文昌A凹陷近十几年来最大的发现,展现了该区良好的勘探前景。

The fault transfer zone developed in extensional basins plays a very important role in hydrocarbon accumulation. A large-scale fault transfer zone is developed in southwest Wenchang A sag, Pearl River Mouth basin in the context of oblique extension. The structural characteristics of the fault transfer zone are studied through fine seismic interpretation, and the reservoir forming conditions are anatomized. The results show that the large-scale fault transfer zone in Wenchang A sag is mainly controlled by two main faults: the south section of Wenchang A sag, Zhu Ⅲ southern fault zone and No.6 fault. The interior of the fault transfer zone is composed of north, middle and south fault zones. Its tectonic evolution has experienced three major stages: Paleocene-Eocene(Shenhu-Wenchang period) tension fracture, Oligocene-Early Miocene(Zhuhai-Zhujiang period) dextral superimposed strike slip, and the strengthening of strike slip and the finalization of the fault transfer zone since the Middle Miocene. The fault transfer zone not only controls the development of traps, but also has a certain impact on source rocks, sedimentary systems and hydrocarbon migration and accumulation. Combined with the hydrocarbon enrichment law of “internal gas and external oil, lower gas and upper oil” in the region, the largest discovery in Wenchang A sag of Pearl River Mouth basin in recent ten years has been obtained in the fault transfer zone, showing a good exploration prospect in this area.