应力作用下气藏水体微观赋存特征及渗流规律——以鄂尔多斯盆地神木气田二叠系盒8段致密储层为例

Microscopic occurrence characteristics and seepage law of water bodies in gas reservoir under stress: a case study of tight reservoirs in the eighth member of Permian Shihezi Formation, Shenmu Gas Field, Ordos Basin

马云峰 赵建国 孙龙 暴玉宁 曹青赟 巩肖可 陈朝兵 王恒力

MA Yunfeng ZHAO Jianguo SUN Long BAO Yuning CAO Qingyun GONG Xiaoke CHEN Zhaobing WANG Hengli

中国石油长庆油田分公司 第二采气厂, 西安 710200 西安石油大学 地球科学学院, 西安 710065 延安大学 石油工程与环境工程学院, 陕西 延安 716000

Second Gas Production Plant, Changing Oilfield Company, PetroChina, Xi'an, Shaanxi 710200, China College of Earth Sciences & Engineering, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China School of Petroleum Engineering and Environmental Engineering, Yan'an University, Yan'an, Shaanxi 716000, China

针对致密气藏衰竭开发过程中储层孔隙结构及流体微观赋存特征随其所受应力大小实时变化的问题，以鄂尔多斯盆地神木气田二叠系石盒子组盒8段致密储层为例，通过核磁共振、高压压汞以及驱替实验，定量表征不同应力条件下孔隙结构、水体动用及束缚水分布特征，分析应力对气水相渗规律的影响。研究表明，有效应力由7 MPa增加至17 MPa后，储层孔隙度由8.39%减小至7.65%，最大孔隙半径由38.3 μm减小至35.2 μm，其中半径为0.3~18.9 μm范围内的孔喉数量减少幅度最大；由于孔喉尺寸减小，参与渗流的孔隙数量减少，束缚水饱和度由51.3%增加至59.7%，束缚水水体尺寸的分布范围由0.012~17.4 μm增大至0.012~20.1 μm；孔隙变化及束缚水分布特征的变化进一步导致气水两相相对渗透率均减小，气相相对渗透率由0.481减小至0.283，等渗点的相对渗透率由0.157减小至0.09。

In order to solve the problem that the pore structure and the microscopic occurrence characteristics of fluid change with stress in real time during the depletion development of tight gas reservoirs, the pore structure, water production and irreducible water distribution characteristics of tight reservoirs in the eighth member of Permian Shihezi Formation, Shenmu Gas Field, Ordos Basin under different stress conditions were quantitatively characterized, and the influence of stress on gas-water relative permeability was analyzed by using nuclear magnetic resonance (NMR), high-pressure mercury injection (HPMI) and displacement experiments. The results show that when effective stress increases from 7 MPa to 17 MPa, reservoir porosity decreases from 8.39% to 7.65%, and the maximum pore radius decreases from 38.3 μm to 35.2 μm among which, the number of pore throats in the range of 0.3-18.9 μm decreases the most. The number of pores involved in seepage decreases due to the decrease of pore throat size, the bound water saturation increases from 51.3% to 59.7%, and the distribution range of the size of bound water increases from 0.012-17.4 μm to 0.012-20.1 μm. The changes of pore structure and bound water distribution characteristics further reduce the relative permeability of both gas and water phases, the relative permeability of gas phase decreases from 0.481 to 0.283, and that of isotonic point decreases from 0.157 to 0.09.

国家自然科学基金 41802140;国家科技重大专项 2016ZX05050006;陕西省自然科学研究基础计划项目 2019JQ-257

https://doi.org/10.11781/sysydz202303466