塔里木盆地满西区块强制海退体系域沉积模式

构造运动、全球海平面变化和气候的相互作用控制了沉积物供给量以及可容空间被充填的规模.在强制海退情况下的缓坡边缘上,相对海平面下降期间过路沉积物未被输送到盆底,而被沉积为一组逐级下降的前积楔,形成强制海退体系域.塔里木盆地满西区块的东河砂岩等时段是基于东河砂岩段上部和下部所存在的层序界面(不整合面)而划分的,具有等时性,但岩性、岩相在不同位置、不同地区会有变化.东河砂岩等时段所属的层序SQ1的层序界面是海平面长期下降的结果,并受到构造运动的加强作用,表现为一个盆地范围内广泛发育的不整合面.层序SQ1的发育演化明显受到海平面变化的控制:在海平面快速上升时期发育海侵体系域;在海平面缓慢下降时期发育强制海退体系域.满西地区的东河砂岩是强制海退体系域的沉积产物,是在海退背景下发育的复合砂体,其展布非常复杂,多数呈点状或块状展布.层序SQ1的油气储集体主要分布于海岸带附近,它们是前滨—临滨沉积砂体.

Depositional model for forced regressive systems tract of Manxi Block in Tarim Basin

The interaction of tectonics,change of global sea level and climate controlled the sediment supply and the scale of filled accommodation.On the ramp margin of forced regressive background,no by-pass sediments were migrated to basin floor during falling of the relative sea level.However there was a set of descending stepwise wedges known as forced regressive systems tracts in the basin.Donghe sandstone equivalent of Manxi Block in Tarim Basin was distinguished on the sequence boundary (unconformity), and it has shown iso-chronology and changes of lithological and litho-facies in the different places.The sequence SQ1 of Donghe sandstone equivalent was resulted from long-term falling of sea level and reinforced by tectonics.It shows a broadly developed basin-scale unconformity.The development of SQ1 was controlled distinctly by sea level changes.The marine ingressive systems tract was developed during fast rising period of sea level,and the forced regressive systems tract was developed during slow falling of sea level.Donghe sandstone of Manxi Block characterized by forced regressive systems tract was the composite sandstone body on the background of marine regression. The composite sandstone bodies were distributed in very complicated shapes,and most of them were developed in point-shape or cake-shape bodies.The oil-target reservoirs of the sandstone body were mainly distributed on the coastal zone and belonged to the shore face sediments.