库车坳陷东部下侏罗统砂体特征与储集层性质的关系

The relationship between the characteristics of sand bodies and the properties of Lower Jurassic reservoirs in eastern Kuqa depression, Tarim basin.

库车坳陷目前已在侏罗系至第三系发现丰富的天然气 ,因此认识下侏罗统沉积砂体的分布规律及其对储集层性质的控制作用对该区天然气勘探极为重要。通过露头调查、取样测试和钻井资料的综合研究认为 ,该区下侏罗统自下而上为辫状三角洲、湖泊三角洲和较深湖沉积组合 ,主要沉积微相为三角洲沉积体系中的辫状分流河道和水下分流河道 ,其次为河口坝。分析该期沉积砂体的时空叠置模式 ,按砂体成因可以划分为 9类砂体 ,其中辫状河道砂体 ,辫状分流河道砂体 ,类曲流河河道砂体和水下分流河道砂体是该区阿合组和阳霞组的主要砂体类型 ;按层序结构分有 5种砂体 ,而据砂体的形态可分为积木式和迷宫式 2种类型。砂体特征对储集层性质的控制作用主要表现在粒径大小上 ,较粗粒级砂岩的储集层性质明显变优。在上述分析的基础上 ,对该坳陷的储集层性质进行了评价 ,提出克 依构造带西段为致密储集层或裂缝性致密储集层分布区 ;东段为优质储集层分布区 ,是下一步的有利勘探方向。这一认识已被钻探结果所证实。图 5表 2参

On the comprehensive analysis of investigating outcrops, testing samples and drilling data, it is considered that the Lower Jurassic sand bodies in eastern Kuqa depression are predominately of braided distributary channel and subaqueous distributary channel subfacies and subordinately of distributary mouth bar subfacies, both of which belongs to braided delta depositional system. They can be subdivided into nine types of sand body according to their genesis; five kinds of sand body according to their sequence structures and two types of jigsaw puzzle and labyrinth reservoir architectures according to their shapes. The control of the characteristics of sand bodies on the reservoir properties is mainly of the grain size,that is the property of relatively coarser sandstones obviously becomes better. So it comes to the conclusion that braided distributary channel and subaqueous distributary subfacies are the good oil and gas reservoir sand bodies.