塔里木盆地库车坳陷中三叠统辫状河三角洲沉积

BRAIDED-RIVER DELTAS OF MIDDLE TRIASSIC, KUQA DEPRESSION, TARIM BASIN

李维锋 高振中 彭德堂 王成善

LI Wei-feng GAO Zhen-zhong PENG De-tang WANG Chen-han

江汉石油学院, 湖北 荆州 434102 2. 成都理工学院, 四川 成都 610059

Jianghan Petroleum University, Jingzhou, Hubei 434102, China 2. Chendu University of Technology, Chendu 610059, China

:塔里木盆地库车坳陷中三叠统广泛发育由辫状河进积到内陆湖泊中而形成的辫状河三角洲。这种三角洲特征显著,明显有别于其它类型的三角洲。辫状河三角洲的主体是由含砾砂岩及中、粗粒砂岩组成的辫状河道沉积及水下分流河道沉积,它们由许多下粗上细的砂岩透镜体在垂向上相互叠置而成,单一透镜体最大厚度在0.5～4m不等。三角洲中交错层理丰富,其中尤以水道砂体侧向迁移加积而形成的侧积交错层异常发育为标志。由于辫状河三角洲形成时物源供给丰富且粒度粗,沉积物堆积速率快,因而湖泊的波浪对其影响改造甚微。三角洲砂体孔隙度及渗透性均好,且整个三角洲砂体分布稳定,为理想的储集层。

Braided river delta that braided river systems prograde into an inland lake were well developed in the Middle Triassic of Kuqa depression,Tarim Basin.Their characters are distinct and significantly different from the other types of deltas.The deposits of braided river deltas are mainly composed of pebbled sandstone and medium coarse sandstones.The bars of the braided channel and subaqueous distributary channel are the main bodies of deltas,and they are composed of many,finning upward lenticular sand bodies that pile vertically up each other.A single lenticular sand body has a thickness of 0.5～4m.Cross stratifications are abundant in the braided river deltas,but lateral accretion cross bedding resulting from lateral accretion of sandbodies are the most principal sedimentary structures and one of the most distinct character of braided river deltas.Because the braided river deltas are characterized by a high rate of coarse sediment input,they are less influenced by the waves of lake.The sandbodies of deltas are very excellent reservoirs in that they have a higher porosity,better permeability and a larger,stable thickness.

国家"八五"科技攻关项目(85-101-01-03)

https://doi.org/10.11781/sysydz200001055