塔里木盆地西部寒武-奥陶系储层分布特征

塔里木盆地西部在寒武-奥陶纪大体经历了两次一定规模的海侵-海退沉积,并相应形成了由4个三级旋回层序和2个二级旋回层序构成的层序地层格架.它不仅控制着不同沉积相的平面展布特征,而且控制着生储盖组合的时空分布规律.下寒武统肖尔布拉克组与吾松格尔组的高水位体系域局限台地相沉积,早期普遍经历了白云岩化作用,及后期大气淡水淋溶的综合改造,形成了平面上展布非常稳定的优质针孔状碳酸盐岩储集层段.奥陶系储层主要形成于高水位体系域开阔台地相、台地边缘相和藻滩相中,由于受海水成岩和埋藏成岩环境影响,胶结作用发育,致使储层整体面貌呈Ⅳ类差储集层.

DISTRIBUTION OF CAMBRIAN-ORDOVICIAN RESERVOIR ROCKS CONTROLLDED BY SEQUENCE STRATIGRAPHY IN WESTERN TARIM BASIN

The western Tarim basin undergone two transgression-regression cycles during the Cambrian-Ordovician , and formed a sequence stratigraphic framework composed of four third-order cyclic sequences and two second-order cyclic sequences, which controlled not only the plane distribution of different depositional facies, but also influenced the spatial and temporal distribution of various associations of source, reservoir and cap rocks. Xiaoerbulake Fm. and Wusonggeer Fm. were limited carbonate platform facies within Highstand System Tract(HST), and they were generally reworked by dolomitization during early time, and superimposed by late meteoric water leaching to form high-quality carbonate reservoir with small needle-like porosity and stable plane distribution. Whereas the Ordovician reservoirs were mainly formed in open platform facies, platform edge facies and algal beach facies, together with the joint influence by marine-burial diagenetic environments, the carbonate rocks were tightly cemented to form low-quality reservoir bed.