考虑有机质和无机质差异的多因素耦合页岩渗透率计算模型  

Calculating model of shale permeability with multi-factor coupling considering difference between organic matter and inorganic matter

作　　者：曹成 郭浩[2] 张亮 CAO Cheng;GUO Hao;ZHANG Liang(College of Mathematics and Computer Science,Shaanxi University of Technology,Hanzhong 723001,China;Yanchang Oilfield Co Ltd,Yan’an 716000,China;Research Institute of Shaanxi Yanchang Petroleum(Group)Co Ltd,Xi’an 710075,China)

机构地区：[1]陕西理工大学数学与计算机科学学院,陕西汉中723001 [2]延长油田股份有限公司,陕西延安716000 [3]陕西延长石油(集团)有限责任公司研究院,陕西西安710075

出　　处：《大庆石油地质与开发》2022年第5期160-167,共8页Petroleum Geology & Oilfield Development in Daqing

基　　金：国家科技重大专项“延安地区陆相页岩气勘探开发关键技术”(2017ZX05039)。

摘　　要：为了揭示多种因素综合影响下的页岩气传输机理,基于单毛细管模型,得到考虑黏性流、自由气扩散、表面扩散、基质收缩、应力敏感、吸附气层厚度、水膜厚度的页岩有机质和无机质渗透率计算模型,将有机质渗透率模型和无机质渗透率模型耦合,得到考虑多因素耦合和差异性基质的页岩渗透率计算模型,并以鄂尔多斯盆地中生界长7页岩层系的岩心实验数据为依据对模型进行验证和讨论。结果表明:在整个页岩气藏开发阶段表面扩散对渗透率的影响都较大,其中表面扩散系数和兰格缪尔压力影响权重最大,这2项参数与渗透率呈正相关;在页岩气藏压力较高阶段,吸附气层厚度对渗透率的减量贡献影响较大,在压力较低阶段,自由气扩散、应力敏感对渗透率增量贡献的影响较大;基质差异对页岩气渗透率计算结果会产生较大的偏差,有机质含量越低,偏差越大,当w (有机质)为5%时,计算结果偏差最高接近40倍。研究认为,重点考虑表面扩散、自由气扩散、吸附气层厚度、应力敏感和差异性基质会得到较准确的渗透率计算结果;在开发初期,通过增加体积压裂规模释放吸附气来获得更高的渗透率从而提高产量,在开发中后期,通过配产使气藏保持合理的压力水平,得到渗透率与驱替压差的最优值,从而提高产量。In order to reveal shale gas transmission mechanism,on the basis of single capillary model,organic and inorganic matters’ permeability calculation models are established considering viscous flow,free gas diffusion,surface diffusion,matrix shrinkage,stress sensitivity,adsorbed gas layer thickness and water film thickness. Organic matter permeability model is coupled with non-matrix permeability model to obtain shale permeability calculation model considering various factors and differential matrix. The established shale permeability calculation model is verified and discussed by experimental data of Chang-7 shale core of Ordos Basin. The results show that surface diffusion has much influence on permeability throughout development stage of shale gas reservoir,of which surface diffusion coefficient and Langmuir pressure have most influence and these 2 parameters are positively correlated with permeability. At the stage of high pressures in shale gas reservoir,adsorbed gas layer thickness has much influence on reduction contribution of permeability,while at low pressure stage,free gas diffusion and stress sensitivity have much influence on permeability increment contribution. Matrix difference results in a large deviation in calculated results of shale gas permeability,the lower the organic matter content is,the more the deviation is. When w(TOC)is 5%,deviation is close to 40 times at most. The study shows that focusing on surface diffusion,free gas diffusion,adsorbed gas layer thickness,stress sensitivity and differential matrix can obtain more accurate permeability calculated results. In early development stage,higher permeability and production can be achieved by increasing scales of volumetric fracturing to release adsorbed gas,while in middle and later development stage,production can be increased by allocating production to maintain rational pressure level to obtain optimal values of permeability and displacement differential pressure and thereby increase production.

关 键 词：页岩有效渗透率 多因素耦合 有机质 无机质 

分 类 号：TE357.12[石油与天然气工程—油气田开发工程]