玛湖凹陷三叠纪古地貌对沉积的分级控制作用

勘探实践证实，玛湖凹陷三叠系百口泉组扇三角洲沉积具有相带控藏控产的特点。针对常规相带刻画技术难以实现对沉积微相的刻画以满足勘探需求的技术难题，利用古地貌恢复，结合钻探资料，开展了古地貌对百口泉组扇三角洲沉积分级控制作用的研究，以实现对扇三角洲前缘相朵叶体的精细刻画。研究表明，百口泉组扇三角洲沉积受古地貌分级控制：（1）山口、沟槽、古凸控制着扇体主槽走向，从而控制着平原相及扇间泥岩带，平台区控制着前缘相带展布，主流线向坡降较大的方向偏移，从而控制着扇体相带的对称性，多级坡折则控制着高低位湖岸线的分布；（2）平台区次级沟谷及坡折等二级古地貌控制着次级主流线的走向，从而控制着前缘相朵叶体的分布。

Hierarchical Control Function of the Paleogeomorphology in Triassic Period to Sedimentary in Mahu Sag

Exploration practice confirmed that Fan delta deposit has the characteristics of facies control of reservoir and production in the Triassic Baikouquan Formation in Mahu Sag. For the technical problem that the conventional sedimentary facies division technology is difficult to achieve the division of sedimentary microfacies in order to satisfy the demand of exploration. With the paleogeomorphology restoration technology and drilling data, we studied the hierarchical control function of the paleogeomorphology to the Fan Delta sedimentary in Baikouquan Formation, and achieved meticulous depiction of the front facies of Fan Delta. Studies indicate that the Fan Delta sedimentary in Baikouquan Formation hierarchically controlled by the paleogeomorphology in Triassic Period. Mountain pass,grooves,convex controls the main channel of Fan Delta,thus controls the plain facies of Fan Delta and the Mudstone between Fan Delta. The Platform Area controls the front facies of Fan Delta. The mainstream line towards the direction of the larger gradient, thus controls the symmetry of Fan Delta. Multistage slope breaks control the location of the hi-lo shorelines. In the platform area, secondary paleogeomorphology, including secondary groove and slope break, controls the subprime mainstream line direction, thus controls distribution of Lobes body in the front facies of Fan Delta.