鄂尔多斯盆地镇北地区长4+5储层微观孔隙结构研究

Microscopic pore structure of the fourth and fifth members of the Yanchang Formation in Zhenbei area of the Ordos Basin

李成 郑庆华 张三 柳益群 汪伶俐 梁晓伟

Li Cheng Zheng Qinghua Zhang San Liu Yiqun Wang Lingli Liang Xiaowei

中国石油长庆油田分公司勘探开发研究院/低渗透油气田勘探开发国家工程实验室, 西安 710018 2. 西北大学大陆动力学国家重点实验室/西北大学地质学系, 西安 710069

National Engineering Laboratory for Permeability Petroleum Exploration and Development/Research Institute of Petroleum Exploration and Development, Changqing Oilf1eld Company, PetroChina, Xi'an, Shaanxi 710018, China 2. State Key Laboratory of Continental Dynamics/Geology Department, Northwest University, Xi'an, Shaanxi 710069, China

鄂尔多斯盆地镇北地区延长组长4+5以成岩型低渗透储层为主,常规方法较难评价该类储层微观孔隙结构品质。利用铸体薄片、扫描电镜和物性分析等方法对影响储层微观孔隙结构特征的因素进行了定性分析,恒速压汞方法对储层微观孔隙结构特征参数进行了定量表征。研究表明:镇北地区长4+5低渗透储层微观孔隙结构与成岩作用密切相关,主要表现为机械压实作用和碳酸盐胶结作用越弱,长石溶蚀作用越强烈,粒间孔和溶蚀孔越发育,孔喉连通性越好,渗透率越大;微观孔隙结构和渗透率受大于0.12μm的喉道控制明显,主要表现为平均喉道半径越大,渗透率越大,孔喉半径比越小,微观孔隙结构越好,储层品质因子越大,试油产液量越高,尤其当平均喉道半径小于1.60μm时。喉道是影响低渗透储层微观孔隙结构品质的主要因素。

The fourth and fifth members of the Yanchang Formation (Chang4+5) in Zhenbei area of the Ordos Basin are low-permeability reservoirs of diagenetic origin. Conventional methods such as thin section analysis, scanning electron microscopy and physical properties determination failed to analyze the microscopic pore structure of these reservoirs. We used conventional methods and applied constant rate mercury penetration to study the controlling factors to quantitatively determine microscopic pore structure. The microscopic pore structure of the Chang4+5 reservoirs was mainly impacted by diagenetic effects. When mechanical compaction and carbonate cementation were weaker and feldspar dissolution was more intense, intergranular pores and dissolution pores would be more developed, resulting in better connectivity and higher permeability. Microscopic pore structure and permeability were mainly controlled by throat radius. Generally, if average throat radius was >0.12μm, permeability would be higher, the smaller the pore/throat radius ratio, the better the microscopic pore structure, the greater the reservoir quality index (RQI), and the higher liquid oil yield, especially when the average throat radius was <1.26μm. Throats controlled the quality of the microscopic pore structure of low permeability reservoirs.

教育部科技发展中心高等学校博导基金(20106101110020)、大陆动力学国家重点实验室(西北大学)重点基金项目(BJ08133-3)、国家自然科学基金项目(41390451)和国家重点基础研究发展计划(973计划)项目(2014CB239003)资助。

https://doi.org/10.11781/sysydz201506729