致密碳酸盐岩储层微观结构特征及发育影响因素——以鄂尔多斯盆地东部马五₁₊₂亚段为例

Microstructure characteristics and development influencing factors of tight carbonate reservoirs: a case study of the Ma 5₁₊₂ sub-member in eastern Ordos Basin

卢子兴 董国栋 裴文超 吴学强 赵伟波 黄道军 陈娟萍 高星

中国石油长庆油田分公司勘探开发研究院，陕西 西安 710018 低渗透油气田勘探开发国家工程实验室，陕西 西安 710018 中国石油长庆油田分公司采气三厂，内蒙古 乌审旗 017300

为了明确鄂尔多斯盆地东部马五1+2亚段致密碳酸盐岩储层发育有利区，应用铸体薄片鉴定、高压压汞、低温液氮吸附及CT扫描的方法，对研究区马五1+2亚段致密碳酸盐岩储层特征进行了系统研究。结果表明：研究区储层岩性以含硬石膏结核白云岩、角砾白云岩（渗流粉砂充填）、砂屑白云岩和细粉晶白云岩为主，其中，含硬石膏结核白云岩为优质储集岩，但其发育程度及规模较有限；角砾白云岩（渗流粉砂充填）储集性能略差，但其分布规模大，更具勘探潜力。主要受沉积环境、成岩作用及不整合3类因素的影响，研究区碳酸盐岩储层与靖边气田相比，角砾化严重，含硬石膏结核白云岩发育厚度明显变小，而且更为致密。结合有利储层的分布特征，优选了榆林—米脂地区为下一步勘探的重点目标区。

In order to identify the favorable development area of tight carbonate reservoirs of the Ma 5₁₊₂ sub-member in eastern Ordos Basin, using casting thin sections, high pressure mercury intrusion, cryogenic liquid nitrogen adsorption and CT scanning, the characteristics of tight carbonate reservoirs of Ma 5₁₊₂ sub-member in the study area were systematically studied. The results show that the reservoir lithology in the study area is dominated by anhydrite-containing nodules dolomite, breccia dolomite ( filled by seepage silt ), sand-debris dolomite and fine silt crystal dolomite, among which the anhydrite-containing nodules dolomite is the best reservoir type, but its development degree and scale are limited. Breccia dolomite ( filled by seepage silt ) has poor reservoir performance, but it has larger distribution scale and more exploration potential. Influenced by the three factors such as sedimentary environment, diagenesis and unconformity, the reservoir in the study area is more breccified than that in Jingbian gas field, and the thickness of the anhydrite-containing nodules dolomite is obviously thinner and the reservoir is more compact. Combining with the distribution characteristics of favorable reservoir, the Yulin-Mizhi area is selected as the key target of the next exploration.

10.6056/dkyqt202303003