珠江口盆地断层封堵特征及其影响因素

珠江口盆地在南东—近南北向拉张应力的作用下形成了北西、近东西和北东向3组断层,其中以正断层为主,正、反向正断层共存。断层两盘的毛管压力差与油气排替压力的关系决定了断层的封堵能力,不同性质的断层在流体运移过程中的作用不同,同一断层在不同时期对流体的控制作用也不同。对珠江口盆地断层的形成机制、发育特征、断面内部结构和应力状态进行了研究,对珠江口盆地断层封堵的特点及其影响因素进行了综合分析。结果表明,封堵盘泥岩含量是断块构造封堵成藏的主要因素,同时断层的断距、起伏状态、走向、倾角、活动时间及次生后期断层均对断层的封堵能力有一定的影响。

Characteristics and influencing factors of fault sealing in Pearl River Mouth Basin

Three groups of faults in north-west, east-west and north-east directions were generated in the Pearl River Mouth Basin under the extending stress in the south-east to south-north trending. The faults are almost the normal faults, and the positive and negative normal faults are coexistence. The sealing capacity of the faults is decided by the difference between threshold pressure and the displacement pressure of hydrocarbon. The different faults have the different effect on the fluid migration, and the same fault as a pathway for hydrocarbon migration at the different time has different capability. It is generally considered that the active fault is open and the stable fault is close. The analyses on the characteristics and the influencing factors for the fault sealing, and the study of stress, inner structure, deformation mechanism of the faults show that the content of clay is the key factor controlling the fault trap with hydrocarbon accumulation. At the same time, fault throw, fault trend, obliquity, activity time and subsequent small fault are also the affecting factors for fault traps in the Pearl River Mouth Basin.