陆相盆地强制性水退对油气的控制作用

Effect of Forced Regression on Hydrocarbon in Non-marine Basins

通过研究钻井、录井和岩心等资料认为姚一段地层为一个完整的三级层序(SY1)。将其划分成低位域、水进域和高位域3个体系域,每个体系域又细分成3个准层序组。研究发现研究区低位域地层沉积是在强制性水退背景下形成的,此时其西部的龙虎泡—大安阶地为沉积滨线坡折带,低位域内3个准层序组依次由老到新向盆地进积,滨岸线也相应的向盆地方向迁移。强制性水退机制作用下形成的砂体大都沉积在沉积滨线坡折带以下的齐家—古龙凹陷内,并逐渐向盆地方向进积迁移。这些砂体直接覆盖在青山口组大套的暗色泥岩之上,青山口组地层暗色泥岩生成的油气直接有效地运移到其上覆的姚一段砂体之中,最终富集成藏。因此强制性水退在松辽盆地北部长垣以西地区对油气有着重要的控制作用。以此为基础可以精确预测非构造圈闭分布。

On the basis of geological and geophysical analysis, it is concluded in this paper that K_1Y_1 is one three-order sequence, which can be divided into 3 parts: the low-stand system tract, transgressive system tract and high-stand system tract. The sequence deposition in low-stand system tract is formed under the environment of forced regression. Meanwhile, Longhupao-Da’an terrace west to the deposition is a sedimentary shoreline knick zone, 3 metasequence groups in low-stand tract prograde from old ones to new, and coastal line migrate towards the basin accordingly. The sand bodies formed under the mechanism of forced regression are mostly deposited in Qijia-Gulong depression, and they prograde towards the basin gradually. These sand bodies overlie the dark mud stone in Qingshakou, hydrocarbon generated in the dark mud stone migrates directly to the overlay Y_1 sand body, and finally hydrocarbon reservoirs are formed. Therefore, the forced regression has important effect on hydrocarbons in the area west to north Songliao basin, and based on this the distribution of non-structural traps can be predicted precisely.