东营凹陷牛庄洼陷砂岩透镜体的成藏机理

Petroleum accumulation mechanism of lens-type sandstone in Niuzhuang Subsag of Dongying Sag

针对济阳坳陷东营凹陷牛庄洼陷砂岩透镜体的含油性及其油气充注程度差异较大、成藏机理复杂的特点,根据成藏动力学和成藏运动学理论,利用动、静态相结合的研究方法对砂岩透镜体的成藏机理进行了探讨。研究结果表明:牛庄洼陷砂岩透镜体油藏主要发育在沙河街组超压系统内,并且围绕断裂带呈环带分布;牛庄洼陷大部分砂岩透镜体油藏具有"混源性"及"它源性"的油源条件;与超压系统周缘的幕式泄流泄压过程相对应,超压系统内烃类物质和地层水构成的混相流体也发生了幕式、自组织运移,并且砂岩透镜体的油气充注过程与地层流体的自组织活动存在着良好的耦合关系;当混相流体穿越砂岩透镜体时,透镜体砂岩与其围岩的接触面具有半渗透膜效应;在半渗透膜效应下,混相流体活动性明显控制着该类油藏的空间分布和油气富集程度。因此,处于超压系统的泄流泄压带以及内侧的砂岩透镜体具有良好的油气勘探前景。

The petroleum accumulation mechanism of lens-type sandstone in Niuzhuang Subsag of Dongying Sag in Jiyang Depression was studied,according to the dynamics and kinematics analysis. The lens-type reservoirs in Niuzhuang Subsag were mainly developed in the overpressure systems of Shahejie Formation and distributed around the fault zones. The biomarkers indicated that oils in the most lens-type reservoirs were not mainly derived from the around source rocks. The geochemical characteristics of oils indicate that there was systemic movement of liquids in the anomalous pressure system. The boundaries of the anomalous pressure system often took place episodic leak of pressure and fluids. Accordingly, the liquids in the anomalous pressure system were also characterized by episodic self-organized migration for the balance of mass and energy. The interface between the lens-type sandstone and mudstone exhibited the effect of the semi-permeable film for transiting the mixed liquid of oil and water. Under the effect of semi-permeable film, the flow rate of the mixed liquid transiting in lens-type sandstone evidently controlled the oil potentials of lens-type sandstone. The lens-type reservoirs were distributed around the leak zone of the anomalous pressure system.