一种预测异常高压发育范围的新方法:以东营凹陷为例

A New Method for Predicting the Development Range of Abnormal High Pressure: A Case Study in the Dongying Sag

成藏期异常压力是油气成藏研究的关键环节,其发育范围预示了成藏期油气运移的主要方向,对预测有利勘探区具有重要的意义。此次研究以东营凹陷为例,应用地球化学分析的方法,依据烃类地球化学特征,建立了异常高压发育范围预测的新方法。首先通过实测资料和地球物理资料相结合,分析了东营凹陷现今压力发育特征,进一步明确了各压力系统划分与范围;然后统计了各压力系统内烃类的地球化学参数特征,分析了其与压力发育的关系,明确异常高压区C_(29)S/R、甾烷C_(27)/C_(29)ββ、Pr/Ph均随压力系数增大而总体呈增大趋势,筛选了划分异常高压区的地球化学指标,并确定了相关指标的参数范围。将本次建立的新方法应用于东营凹陷油气成藏的研究表明,东营凹陷成藏期流体异常高压的发育范围在横向、纵向的波及范围都大于现今异常高压发育范围,且主要延伸区域多位于斜坡带,这为有利勘探目标区的优选提供了重要依据。

Abnormal pressure is one of the critical issues in oil-gas reservoir formation, and its development range indicates the maindirection of oil-gas migration and thus is important to the prediction of favorable exploration areas. Based on a case study in theDongying sag, a new method for the prediction of abnormal pressuredevelopment range is established by using hydrocarbongeochemistry. First, combined the measured pressure with the geophysical data, the present pressure development characteristics in theDongying sag were analyzed to determine the division and scope of pressure systems. Second, according to the statistical features ofhydrocarbon geochemical parameters within the pressure systems, their relationship with pressure development were analyzed. Resultsshow that the sterane C_(29)S/R, sterane C_(27)/C_(29) and Pr/Ph ratios are positively correlated to pressure coefficient in abnormally highpressure zones. Geochemical parameters were screened for the division of abnormally high pressure zones and the correspondingvaluerangeswere determined. This new methodology was further applied in the Dongying sag. Results show that the development scope ofabnormally high pressure is larger than the present abnormally high pressure zone either horizontally or vertically. The main extensionareas locate in the slope zone. This provides new important information for predicting favorable exploration targets.