顺北地区中下奥陶统埋深碳酸盐岩储集体特征及成因

Characteristics and Genesis of Deep Carbonate Reservoirs in Shunbei Area

为明确储集体特征及其成因,利用岩心及薄片观察、X衍射、物性测试、阴极发光和Sr同位素测试等技术手段对塔里木盆地顺北地区不同断裂带位置典型井碳酸盐岩储集体储集空间影响因素进行分析。研究表明,储集体岩性以砂屑泥晶灰岩、泥晶砂屑灰岩和泥晶灰岩为主,储集空间类型包括洞穴、裂缝和孔洞,充填物类型主要为方解石、沥青和石英。其中:方解石胶结最为常见、分布广泛,存在2~3期胶结;沥青和石英在不同储集空间内差异明显,前者仅在裂缝系统内充填,后者几乎全部充填于溶蚀孔洞内。顺北地区一间房组和鹰山组上段储集体类型主要为裂缝型和裂缝-孔洞型,储集体形成主要受断裂-裂缝体系和流体性质、来源及规模影响。断裂-裂缝体系直接控制裂缝型储集体的发育,可提高储集体渗透性并为流体或油气的充注提供通道,是储集体发育的主要控制因素;在断裂通道背景下,流体对储集体的溶蚀作用也会影响储集体的发育,其中碱性富钙流体对研究区储集体发育影响最大,酸性富硅和成烃流体总体规模有限,仅在局部对储集体进行改造。

In order to clarify the reservoir characteristics and its genesis,the factors affecting the development of carbonate reservoirs in different fault zones at the north of Shunbei area were analyzed by means of core and thin section observation,X-ray diffraction,physical property test cathodoluminescence,and Sr isotope testing.The reservoir lithology is mainly composed of bioclastic micrite limestone,micrite sandstone limestone,and micrite limestone.The reservoir space types include caves,fractures,and holes.The main type fillings are calcite,organic asphalt,and siliceous quartz,among which calcite cementation is the most common and widely distributed with 2-3 times of cementation.The difference between the fillings of asphalt and siliceous is obvious in different reservoir spaces.The former fills only in the fracture system,while the latter fills almost entirely in the dissolution cavities.The reservoir body types of Yijianfang and Yingshan Formations are mainly of fracture type and fracture-hole type.The reservoir formation is mainly affected by fault-fracture system,fluid properties,source,and scale.Fault-fracture system directly controls the development of fractured reservoir,which can improve reservoir permeability and contribute to formation through providing a channel for fluid or oil and gas filling,and is a main controlling factor for reservoir development.Under the background of fracture passage,fluid transformation also has some influences on reservoir development.Among them,alkaline calcium-rich fluid has the greatest influence on reservoir development in the study area.The overall scale of acid silicon-rich and hydrocarbongenerating fluids is limited,so only partial reservoir modification is carried out.