摘要
为研究碳酸盐岩储层应力敏感性及其对气藏产能和气井见水的影响,选取塔里木盆地和田河气田奥陶系钻井岩心,开展了应力敏感性研究,结合实验结果及数学推导建立了裂缝开度和有效应力之间的力学关系模型,最终借助有限元方法,对持续开发过程中碳酸盐岩储层裂缝开度的空间变化规律进行了模拟分析。结果表明:裂缝开度的变化随围压或有效应力变化呈非线性关系;随着围压或有效应力的升高,裂缝开度不断减小,0～0.8 MPa之间减小速度快,岩样应力敏感性强,到2.6 MPa或5.4 MPa后变化趋于稳定,说明高应力环境下,岩样的应力敏感性减弱,塑性变形特征明显;随着围压的逐渐降低,裂缝开度不断增大,但不能恢复至初始情况;未来若干年内随着快速开采,和田河气田有效应力增大,裂缝闭合,产能下降;随着生产井关闭或开采速度放缓,气水界面之上有效应力仍然降低,裂缝闭合,界面之下有效应力增大,裂缝开启,底水上升,破坏气藏生产。建议在裂缝性碳酸盐岩气藏开发政策的制定过程中,一方面要开展裂缝分布精细研究,分析裂缝应力敏感性主控因素,同时要制定合理的开发方式和开采速度,确保气藏稳产、高产。
To investigate the stress sensitivity of carbonate reservoir as well as its effect on oil and water productivities, seven rock samples from the Upper Ordovician Lianglitage Formation of the southwestern Tarim Basin were selected for sensitive experiment. Based on the experimental results and mathematical derivation, the relationship between stress-strain and fracture aperture of rock was established. Spatial distribution of fracture aperture under various confining pressure and pore pressure was simulated through finite element method. Results show that effective stress and fracture aperture change rate have a good inverse nonlinear proportional relationship. Along with the increase of confining pressure, the fracture aperture decreases continuously, with a fast decreasing rate at the initial stage (0-0.8 MPa). This indicates that the stress sensitivity of rocks is strong. To a high pressure (2.6 MPa or 5.4 MPa), the aperture changes only a little, implying that the stress sensitivity is weakened under high stress and the plastic deformation is obvious. With the decrease of confining pressure, the fracture aperture tends to be opened till to a zero pressure, but the aperture cannot be restored to the initial state. This is indicative of certain plastic deformation. In the next few years, with continuous and rapid exploitation in the Hetianhe Gas Field, the effective stress will increase, the fractures will tend to be closed and the productivity will decline. However, along with discontinuous mining or manual well shutdown, the effective stress above the gas-water interface will still decrease and the fractures tend to be closed. In contrast, the effective stress below the interface will increase, fractures tend to be opened and bottom water rises to destroy the gas reservoir production. As such, we suggest that a fine study on the fracture distribution and the main controls for fracture stress sensitivity must be carried out when shaping development plan for fractured carbonate gas reservoir. Meanwhile, reasonabl
作者
冯建伟
孙致学
王焰东
佘姣凤
FENG Jianwei;SUN Zhixue;WANG Yandong;SHE Jiaofeng(School of Geosciences, China University of Petroleum, Qingdao 266580, China;Research Institute of Exploration and Development, PetroChina Tarim Oilfied Company, Korla 841000, China)
出处
《高校地质学报》
CAS
CSCD
北大核心
2019年第2期276-286,共11页
Geological Journal of China Universities
基金
国家自然科学基金面上项目(41572124)
中央高校基本科研业务费专项资金(17CX05010)
国家重大专项(2016ZX05047-003
2016ZX05014002-006
2017ZX05013-006)联合资助
关键词
碳酸盐岩
CT扫描
裂缝开度
应力敏感性
数值模拟
carbonate reservoir
CT scanning
fracture aperture
stress sensitivity
numerical simulation
