【摘要】 三叠系延长组长8段是鄂尔多斯盆地西南部主要产油层之一。前人根据露头、钻井资料的矿物成分和含量统计认为长8段为南西—北东走向的三角洲前缘分流河道沉积。以往通常是将有利的河道砂岩储层描述为南西—北东向延伸的直线状。但首次获得镇泾地区南部红河三维地震资料后,综合钻井资料得出了多种方向、形态的主河道砂体展布。结合区域长8段地层的展布、古构造和湖泊发育状况,认为红河三维地震区的长8段为辫状河—曲流河沉积,河道砂体宽厚比为1/500~1/1000,长8段河道呈南东、南北、近东西多种方向,优质储集体为心滩式纵坝砂体,漫滩及河道边部砂体物性较差。镇泾地区长8段湖相及三角洲相沉积不发育。更多还原

【Abstract】 Member C8 of Triassic Yanchang Formation isan important oil production pay zone in the Southwestern Ordos Basin.Based on mineral elements and content from logging and outcrop data,earlier researchers considered its sandstone as deltaic distributary channel deposition flowing from southwest to northeast.So the sandstone distribution was mapped as linear and parallel deltaic distributary channels spreading in NE direction.But based on the interpretation of the newly acquired 3Dseismic and drilling data,sandbodies of the main channel were depicted with different shapes and different directions. Associated with Triassic paleostructrual and paleogeographic background of the basin,it is considered that the Member C8 belongs to a braided-meandering river system,flowing eastward in upstream,and branching radially in downstream.The width to thickness ratio of sandbodies ranges from 1/500 to 1/1000. Thicker sandstone reservoirs are constructed by amalgamated longitudinal bar. Toward the downstream channel sandstones become rare and thin.In the southwestern basin no lacustrine and deltaic facies occurred during Member C8 deposition.更多还原