番禺低隆起PY30-1构造热流体活动证据及油气成藏

PY30-1构造是珠江口盆地番禺低隆起一个发育底辟体的重要含油气构造，为揭示其油气成藏规律，在确定该构造存在热流体活动的基础上，研究其油气来源和超压演化，并进一步分析油气成藏过程。镜质体反射率（Ro）、蒙脱石—伊利石矿物不正常转换和流体包裹体均一温度均指示PY30-1构造存在多期热流体活动，热流体活动的同时伴随烃类的运移。油源分析结果表明PY30-1构造中的油气主要来自白云凹陷恩平组煤系烃源岩，文昌组泥岩为次要烃源岩。地层压力演化史模拟结果表明：由于受珠琼运动二幕、南海运动和东沙运动的影响，白云凹陷存在3期压力释放过程，分别是在距今37～40 Ma、31～33 Ma和0～16 Ma，最后一期压力释放与油气充注期具有很好的一致性。研究认为PY30-1构造中的油气是东沙运动引起白云凹陷压力释放，使得烃类从烃源岩中排出沿底辟构造中的断裂垂向运移的结果。图7参23

Evidence for hot fluid activities and the hydrocarbon accumulation in the PY30-1 structure of Panyu Low Uplift, Pearl River Mouth Basin

PY30-1 structure, accompanied with the development of diapirs, is an important petroliferous structure. To clarify the process of hydrocarbon accumulation, hot fluid activities were confirmed in the PY30-1 structure of the Panyu Low Uplift, the origin of oil and gas and the evolution of overpressure were studied and the hydrocarbon accumulation was analyzed. Hot fluid activities occurred in the PY30-1 structure, as evidenced by vitrinite reflectance (Ro), smectite - illite mineral abnormal transformation, and fluid inclusion homogenization temperatures. Migration of hydrocarbons happened with the hot fluids activities. The source rocks of the oil and gas in the PY30-1 structure are dominantly the Enping Formation lacustrine mudstones, secondarily the Wenchang Formation mudstones. The formation pressure evolution modeling reflects that there are 3 stages of overpressure release at 40-37 Ma, 33-31 Ma and 16-0 Ma under the influence of the second phase of the Zhuqiong movement, the Nanhai movement, and the Dongsha movement. The third stage of overpressure release is coincident with the hydrocarbon charging times. The hydrocarbon accumulation in the PY30-1 structure is that that the hydrocarbon expulses from the source rocks because of overpressure release in the Baiyun Depression under the influence of the Dongsha movement and then migrates vertically through the faults in diapirs.