松辽盆地异常压力系统及其形成原因探讨

Three Abnormal Pressure Systems Developed in the Songliao Basin, Northeast China and Their Genesis

松辽盆地泥岩声波时差反映盆地纵向上存在四套欠压实泥岩,即嫩江组一、二段泥岩,青山口组一段泥岩,泉头组一、二段泥岩和登楼库组一、二段泥岩.泥岩欠压实顶界面位于1000m左右,向盆地东部有逐渐抬高的趋势,局部地区位于800m附近.钻杆测试数据(DST)、重复地层测试数据(RFT)反映盆地储层压力系统以龙虎泡阶地和大庆长垣为界,分为西部斜坡带常压-低压系统(压力系数<1.06)、齐家古龙凹陷-大庆长垣高压系统(压力系数>1.06)和三肇凹陷及其以东的低压-异常低压系统(压力系数<0.96).分析这种特殊压力结构的原因及其对油气运移聚集的影响,认为晚期构造活动是形成松辽盆地特殊流体动力场空间分布特征的触发器,嫩江组沉积末期以来东部斜坡带和西部斜坡带的抬升剥蚀作用与水热效应结合是形成松辽盆地异常低压的主要原因,而泥岩生烃作用是形成齐家古龙凹陷异常高压系统的主要原因.

There exist three under-compacted mudstones in the Songliao basin rectified by the sonic curve of the mudstonethey are mudstone of the first and second Member of the Nenjiang Formation,the first Member of the Qingshankou Formation,the first and second Member of the Quantou Formation and the first and second Member of the Denglouku Formation. The mudstone becomes under-compacted when its buried depth is greater than 1000m at the west part of the basin, while this burial depth can be as shallow as 800m in the east part of the basin. Drill Stem Test （DST） and Repeated Formation Test （RFT） show that the formation pressure can be classified into three regions from west to east divided by the I,onghupao Step and the Daqing Anticline. The west slope zone that lies to the west of the I,onghupao Step is normal-under pressure systems with the pressure coefficient lower than 1. 06. And the area lies to the east of the Daqing anticline is underpressure systems with the pressure coefficient lower than 0. 96, while the area lies between is overpressure system with most of the pressure coefficient greater than 1.06. The above special distribution of the pressure system developed in the Songliao basin is resulted from the late stage tectonic movement. Tectonic uplifting and erosion ever since the Late Cretaceous is the main cause that generates the underpressure systems developed in the West uplifted zone and Southeast uplifted zone of the basin. Maturation of the mudstone is the main cause that generate the overpressure system developed in the West depression of the Songliao basin. The mechanisms that have generated abnormal pressure systems and their influence to the petroleum systems developed in the Songliao basin have been discussed carefully.