麦盖提斜坡东部构造带奥陶系岩相、成岩作用带与储层成因

Lithofacies,diagenesis zone and reservoir origin of the Ordovician in eastern tectonic belt of the Maigaiti slope

通过对塔里木盆地麦盖提斜坡碳酸盐岩2口区探井断裂样式、地层特征、沉积亚(微)相、成岩作用、储集体特征等详细研究,得出以下认识。鹰山组为一套开阔台地的台内滩-滩间海的沉积,蓬莱坝组为局限台地的云坪、云灰坪及粒屑滩沉积。中、下奥陶统成岩作用主要有海底胶结、早期大气淡水溶解与胶结、压实与压溶、两期表生大气水岩溶、埋藏作用和热液改造作用等。受多期构造运动影响,开放与相对封闭的成岩相带可存在于同一碳酸盐岩层段中,前者厚度小、层段多,后者厚度大,层段少。储层受多期不整合面、断裂、裂隙以及水-岩相互作用等因素的控制,有效储集体的成岩序列为海底胶结作用-压实、压溶作用-二期表生大气水岩溶作用-埋藏溶蚀及热水(液)作用等。岩溶相带储层主要发育于在断褶带顶部、褶皱翼部断裂带或断裂与高频层序界面的叠加带,是一种多期构造控制下的渗流带与落水洞叠加的岩溶模式。

Through the detailed research of fracture style,strata feature,sedimentary facies（ microfacies）,diagenisis process and reservoir characteristics of two exploratory wells in carbonate rocks of Maigaiti slope,the following conclusions can be obtained. The Yingshan Formation consists of a set of intra-platform beaches-inter-beach seas of open platform,and the Penglaiba Formation consists of dolomite flat,dolomite-limestone flat and granule shoal. The diagentic processes in Lower and Middle Ordovician mainly include submarine cementation,early atmospheric fresh water dissolution and cementation,compaction and pressure solution,two periods of atmospheric water karstification,burial and hydrothermal modification. Due to the influence of multiphase tectonic movements,open and relative closed diagenetic facies could coexist in the same limestone. The open diagenetic facies feature in small thickness and multiple intervals. In contrast,the closed diagenetic facies is characterized by large thickness and less intervals. The quality of reservoir was controlled by muti-phases unconformities,faults,fractures and water-rock interaction,so the effective reservoir diagenetic sequences were submarine cementation,compaction and pressure solution-two periods atmospheric water karstification,buried dissolution and hydrothermal reformation. Karst reservoir facies zones were mainly distributed in the superimposed tectonic belt between fault fold top,folding wing or fracture with high frequency sequence boundary,and show a karstification model featuring in superimposition of vadose zone and water hole under the control of multiphase tectonic movements.