油气二次运移的驱动机制转换及其石油地质学意义——以牛庄洼陷及其南缘为例

含油气盆地内可以存在多个油气成藏动力系统,相应地油气二次运移的主要驱动机制也不尽相同。驱动机制转换是油气穿越不同成藏动力系统发生运移的动力学纽带,也是进行系统与系统间能量传递和油气运移规律的研究。基于地层流体压力、原油地球化学特征、油气显示和钻测井等资料,经过对济阳坳陷牛庄洼陷及其南缘地区古近系的油气成藏动力系统分析,发现在异常流体压力系统边缘存在着油气运移由超压驱动向浮力驱动的转换过程。在驱动机制转换过程中,烃类物质首先从超压驱动的油、气和水混相流体中分离,在油源断层附近的输导层内经历了短暂停留和聚集后,然后在自身浮力驱动下发生继续运移,相应烃类物质经历的地质色层效应增强。对成藏动力系统间油气驱动机制转换的研究将加深油气运移过程中关键环节的认识,从而更加精细追踪油气运移路径。另外,驱动机制转换过程揭示出在成藏动力系统边缘具有复杂的油气成藏动力学条件和良好的油气勘探前景。

Transformation of Driving Mechanism for the Second Petroleum Migration and Its Significance in Petroleum Geology--Taking the Niuzhuang Sag as an Example

A couple of petroleum dynamic systems can occur simultaneously in one petroliferous basin,and accordingly,main driving mechanism of petroleum secondary migration may differ;this paper studied the rule of energy transfer and gas-oil migration between different systems.Based on liquid pressure survey,petroleum geochemical characteristics,well drilling and logging,analysis on dynamic system of low Tertiary in the Niuzhuang depression and its southern margin of Jiyang,the study has revealed that a transformation from ultra-high pressure to buoyancy occurred in the pressure paralimbic system of anomalous fluid.During the driving mechanism transformation,miscible phase fluid derived form ultra-pressure fluid dynamic system separated firstly from the mixture of petroleum,gas and water,and then resumed to migrate by buoyancy after a short settlement and accumulation in transport layer adjacent to oil source fault,resulting in strengthening geological chromatographic effect.Studying on driving mechanism transformation helps us better understanding petroleum migration and its characteristics,which facilitates our tracing in detailed to migration path of petroleum.In addition,complicate dynamic condition reveals that paralimbic dynamic system is of complicated petroleum reservoir condition and exploration prospect.