塔里木盆地台盆区三叠系大型辫状河三角洲沉积特征

Sedimentary characteristics of the Triassic braided river delta in Tarim Basin Platform

辫状河三角洲是陆相沉积盆地重要的油气储集类型和油气勘探目标。综合运用岩心、测井、地震及分析化验资料,本文认为塔里木盆地台盆区三叠系在宽浅型拗陷湖盆背景下发育大型浅水辫状河三角洲沉积;台盆区总体处于沉积坡度较缓、水体较浅的沉积环境,辫状河三角洲砂体持续地由盆地周缘向盆地中央方向远距离推进,沉积了砂砾质的、具大型交错层理、粗粒间断正韵律和典型下切谷或前积地震反射特征的进积型辫状河三角洲,且以水下分流河道砂体为骨架砂体;文章还探讨了该类型三角洲亚相和微相沉积特征;最后划分并评价了塔里木盆地有利的岩性地层圈闭区。

Braided river delta is an important reservoir type and hydrocarbon exploration target in continental sedimentary basins.Using core,log,and seismic data,this paper indicates that the braided river delta in the Triassic of platform area in Tarim Basin was deposited extensively in the shore-shallow lake background.The platform is generally in the sedimentary environments with in a gentle slope and shallow water.Sand bodies of braided river delta extended continuously from the periphery to the center of the basin.Progradational braided river delta was deposited which has the typical characteristics of arenaceous-conglomeritic sediments,large cross bedding,coarse intermittent positive rhythm,as well as typical incised valley or progradational seismic reflectance signatures.And sand bodies of underwater distributary channel are the backbone ones.The characteristics of sedimentary subfacies and microfacies are also discussed in the paper.At last,favorable lithologic and stratigraphic traps in the platform area are divided and evaluated.