准噶尔盆地乌夏地区中上二叠统碎屑岩成岩作用及次生孔隙演化

准噶尔盆地乌夏地区中上二叠统碎屑岩储层埋藏深，物性差，以次生孔隙为主，成岩作用是影响中深部储层次生孔隙发育的最主要因素。铸体薄片、扫描电镜、X射线衍射等微观研究表明乌夏地区中上二叠统储层碎屑岩成分及结构成熟度均较低，次生孔隙发育，下乌尔禾组和夏子街组的平均孔隙度分别为8.15%和7.85%，其中次生孔隙分别占下乌尔禾组和夏子街组总孔隙的77.18%和80.90%，孔隙增生量平均值分别为6.49%和4.74%。研究区碎屑岩储层主要处于中成岩阶段A-B期，成岩作用以压实作用、胶结作用及溶蚀作用为主，压实作用造成的孔隙度损失平均约为24.5%，胶结作用造成的孔隙度损失平均约为6.14%，溶蚀作用以长石和岩屑颗粒的溶蚀为主，其产生的孔隙增生量对下乌尔禾组和夏子街组的贡献率分别为47.62%和55.86%。研究区受大气水溶蚀、断裂带及有机酸溶蚀作用的影响，在纵向上形成3个次生孔隙发育带。次生孔隙发育带是研究区在低孔低渗条件下寻找相对有利储层的重要区带。

Diagenesis and secondary pore evolution of Middle and Upper Permian clastic rocks in Wu-Xia area,Junggar Basin

The Middle and Upper Permian clastic reservoirs in Wu-Xia area of Junggar Basin are deeply buried and poor in reservoir properties,mainly with secondary pores. Diagenesis is the most important factor affecting the development of secondary pores in middle-deep reservoirs. Based on casting thin section identification,scanning electron microscopy(SEM),X-ray diffraction analysis method with logging and mud logging data,the diagenesis and secondary pore evolution of the Middle and Upper Permian clastic rocks in Wu-Xia area were studied. The results show that the reservoir compositional maturity and textural maturity were low and the most pores were secondary pores. The average porosity of lower Urho Formation and Xiazijie Formation was 8.15% and 7.85% respectively,secondary pores account for 77.18% and 80.90% respectively,and the amount of hyperplasia of pores was 6.49% and 4.74% respectively. The clastic reservoir in the study area was mainly at the A-B stage of the middle diagenetic stage,and the diagenesis was dominated by compaction,cementation and dissolution. The degree of porosity loss caused by compaction and cementation was 24.5% and 6.14% respectively. Dissolution was the main cause of secondary pores and the dissolution of feldspar and debris particles contributed the most to secondary pore growth. Lower Urho Formation and Xiazijie Formation have the rate of 47.62% and 55.86% respectively. Affected by atmospheric water dissolution,fault zone and dissolution of organic acids,there are three secondary pore development zones vertically developed in the reservoir of the study area. The secondary pore development zones are important zones for finding relatively favorable reservoirs under low porosity and low permeability conditions.