松辽盆地十屋断陷异常低压体系及其成因机制

Underpressure System and Forming Mechanism in the Shiwu Depression of Songliao Basin

松辽盆地东南隆起区十屋断陷发育异常低压体系 ,实测的地层压力梯度介于 0 .0 0 5～ 0 .0 0 8MPa/m .研究结果表明异常低压体系的形成既与地温梯度的降低有关 ,又与新生代该区的地层抬升和剥蚀有关 .此外 ,天然气扩散作用对局部异常低压体系的形成具有一定的影响 .研究区地层压力系统演化经历了从异常高压向异常低压演化过程 ,这一过程决定了盆地不同演化时期的水流系统及其油气运聚特征 ,从而使得十屋断陷具有石油成藏早且主要分布于断陷边缘。

Underpressure system developed in the Shiwu depression of Songliao basin with measured formation pressure gradient ranging between 0.005 MPa/m to 0.008 MPa/m. This research result shows that the genetic mechanism of abnormal low pressure attributes to reduction of paleothermal gradients, uplift and erosion during Eocene period. Moreover, gas diffusions also affect the formation of underpressure system at local part. This system at present indicates the evolution process from overpressure to underpressure, which controls fluid flow and hydrocarbon migration in different stages of the depression. Hence, oil pools generating at early stage occur at the basin margin, and gas pools generating at late stage at central part of the Shiwu depression, Songliao basin.