塔里木盆地塔中10号构造带志留系柯坪塔格组低渗储层特征及控制因素

Characteristics and controlling factors of low-permeability reservoirs in Silurian Kepingtage Formation, 10th tectonic belt in the Tazhong area, Tarim Basin

综合运用岩心观察、薄片鉴定、扫描电镜、阴极发光以及物性测试等方法,对塔里木盆地塔中10号构造带志留系柯坪塔格组上段低渗储层的基本特征进行研究,并从沉积、成岩和构造作用3方面开展储层控制因素分析。塔中10号构造带柯坪塔格组上段低渗透砂岩储层主要由岩屑砂岩和岩屑石英砂岩组成,属于低孔低渗储层。储集空间主要为残余原生粒间孔、粒间溶孔和构造微裂缝。储层发育主要受控于沉积作用、成岩作用和构造作用,潮道和砂坪微相形成于强水动力环境,原生孔隙发育且后期酸性溶蚀作用明显,储层物性好,是优质储层发育的有利部位;压实和胶结作用使孔隙减少,而溶蚀作用可以改善储层物性;构造作用形成的微裂缝可以提高储层的渗流能力,对改善储层的储集性能起到一定的建设性作用。

The basic characteristics of low-permeability reservoirs in the upper unit of Silurian Kepingtage Formation, 10th tectonic belt in the Tazhong area were investigated and the controlling factors associated with sedimentology, diagenesis and tectonism were determined based on core observation, thin section, scanning electron microscopy (SEM), cold-cathode luminescence microscopy (CL) coupled with petro-physical property testing. The results indicate that the low-permeability sandstone reservoirs are mainly composed of litharenite and sublitharenite and the studied reservoirs belong to low-porosity and low-permeability reservoirs. The reservoir space mainly includes residual primary pores, intergranular dissolution pores and tectonic microfractures. The reservoir development was controlled by sedimentology, diagenesis and tectonism. The reservoirs in tidal channel and sand-flat microfacies deposited in strong hydrodynamic environments have substantial primary pores and obviously later acidic dissolution. The resulting reservoirs have good petro-physical properties and are targets for high-quality reservoirs. The controlling factors associated with diagenesis are evidenced by porosity reduction due to compaction and cementation, whereas the reservoir petro-physical properties can be enhanced by dissolution. Microfactures induced by tectonism can improve permeability capability and play some positive role in enhancing reservoir petro-physical properties.