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基于孔隙结构的页岩渗透率计算方法
孙海,姚军,张磊,王晨晨,孙致学,闫永平,庞鹏
0
(中国石油大学石油工程学院,山东青岛 266580;中国石油大学地球科学与技术学院,山东青岛 266580;长庆油田分公司油气工艺研究院,陕西西安 710021)
摘要:
采用修正表观渗透率的达西定律可描述气体在致密页岩中的运移机制。表观渗透率可用固有渗透率和孔隙度表示,而常规的试验方法无法准确测量页岩气藏的固有渗透率和孔隙度。提出一种基于孔隙结构图像的页岩固有渗透率、孔隙度和表观渗透率计算方法,首先基于X射线衍射和扫描电镜分析页岩岩心的矿物组成和孔隙结构,采用马尔科夫链蒙特卡洛方法构建页岩三维数字岩心,并应用格子Boltzmann方法计算数字岩心的孔隙度和固有渗透率,得到固有渗透率和孔隙度的关系式并计算页岩的表观渗透率。结果表明:页岩中孔隙主要为纳米级孔隙和微米级孔隙;努森数小于0.01时表观渗透率等于固有渗透率,此时达西定律仍然适用;努森数大于0.01时,数值越大,表观渗透率系数越大,此时达西定律不再适用;固有渗透率越小,压力越小,表观渗透率系数越大。
关键词:  数字岩心  页岩气  格子Boltzmann方法  马尔科夫链蒙特卡洛方法  渗透率
DOI:10.3969/j.issn.1673-5005.2014.02.014
投稿时间:2013-05-26
基金项目:国家自然科学基金重点项目(51234007);教育部博士点基金项目(20110133120012);中国石油大学(华东)自主创新项目(11CX05007A);国土资源部海洋油气资源与环境地质重点实验室开放基金项目(MRE201207)
A computing method of shale permeability based on pore structures
SUN Hai,YAO Jun,ZHANG Lei,WANG Chen-chen,SUN Zhi-xue,YAN Yong-ping,PANG Peng
(School of Petroleum Engineering in China University of Petroleum, Qingdao 266580, China;School of Geosciences in China University of Petroleum, Qingdao 266580, China;Oil & Gas Technology Research Institute of Changqing Oilfield Company, Xi 'an 710021, China)
Abstract:
A modified Darcy 's law with apparent permeability is used to describe the gas transport mechanisms in tight shale rocks, and the apparent permeability can be correlated to the intrinsic permeability and porosity of the rocks, which are difficult to measure using conventional experimental methods. A new computing method for the intrinsic permeability, porosity and apparent permeability of shale was proposed based on the data obtained from pore structure images. Firstly, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the mineral compositions and pore structures of a shale rock sample. Then a 3D digital rock was constructed using the Markov chain Monte Carlo (MCMC) method,and the rock 's parameters, such as intrinsic permeability and porosity, were calculated using the lattice Boltzmann method (LBM). Finally, a model of the correlation between the intrinsic permeability and porosity of the shale rock was established, and the apparent permeability was calculated. The results show that the main pores in the shale matrix can be classified as nano-micro pores. The apparent permeability is found, when the Knudsen number is less than 0.01, to be equal to the intrinsic permeability, and the Darcy 's law can be used. When the Knudsen number is higher than 0.01, the Darcy 's law cannot be used, and the higher the Knudsen number and the smaller the intrinsic permeability and pressure, the bigger the deviation between the apparent permeability and the intrinsic permeability.
Key words:  digital rock  shale gas  lattice Boltzmann method  Markov chain Monte Carlo method  permeability
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