页岩气储层孔隙度测试方法关键参数优化  

Optimization of key parameters for porosity measurement of shale gas reservoirs

作　　者：周尚文[1,2] 董大忠 张介辉[3] 邹辰 田冲 芮昀 刘德勋 焦鹏飞 ZHOU Shangwen;DONG Dazhong;ZHANG Jiehui;ZOU Chen;TIAN Chong;RUI Yun;LIU Dexun;JIAO Pengfei(PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;CNPC Key Laboratory of Unconventional Oil&Gas,Langfang,Hebei 065007,China;PetroChina Zhejiang Oilfield Company,Hangzhou,Zhejiang 311100,China;Shale Gas Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610051,China)

机构地区：[1]中国石油勘探开发研究院 [2]中国石油非常规油气重点实验室 [3]中国石油浙江油田公司 [4]中国石油西南油气田公司页岩气研究院

出　　处：《天然气工业》2021年第5期20-29,共10页Natural Gas Industry

基　　金：国家科技重大专项“页岩储层定量表征及评价”(编号:2017ZX05035002-002)。

摘　　要：孔隙度是页岩气储层评价和储量计算的关键参数,对其准确测试是计算页岩气地质储量和确定开发方案的基础。为了明确不同页岩孔隙度测试方法的差异及其对页岩气储量计算结果的影响,选取四川盆地南部昭通国家级页岩气示范区6口页岩气井共计65个下志留统龙马溪组页岩样品开展了气测、液测和核磁共振3种孔隙度测试方法的对比实验,并根据测试结果对3种方法进行了对比分析,进而提出了优化3种页岩孔隙度测试方法的关键参数。研究结果表明:①气测法页岩样品颗粒大小应介于20~60目,氦气饱和平衡时间大于1800 s;②液测法样品在温度为110℃的条件下烘干时间不少于48 h,采用15 MPa围压进行24 h的加压饱和;③核磁共振法在优化回波时间和等待时间的基础上,应扣除干燥样核磁共振信号后进行核磁共振孔隙度计算;④3种页岩孔隙度测试方法的孔隙度平均值和中位数关系为:液测孔隙度>核磁共振孔隙度>颗粒气测孔隙度>柱塞气测孔隙度;⑤不同页岩孔隙度测试方法对页岩气地质储量计算的结果亦有较大的影响,相差程度可达20%。结论认为,核磁共振法和液测法测试过程中需引入流体进行饱和因而有可能会对页岩孔隙产生破坏,而颗粒样气测孔隙度则能较全面地反映页岩的全部空间且不受外加流体性质的影响,建议采用后者进行页岩气地质储量的计算。Porosity is a key parameter in shale gas reservoir evaluation and reserve calculation and its accurate test is the basis for calculating geological reserves of shale gas and determining development plans.In order to clarify the differences between different porosity test methods and their influences on the calculation results of shale gas reserves,we collected 65 shale samples of Lower Silurian Longmaxi Formation from six shale gas wells in the Zhaotong National Shale Gas Demonstration Area of the southern Sichuan Basin for comparative experiments using three porosity test method,including gas injection porosimetry(GIP)method,water immersion porosimetry(WIP)method and nuclear magnetic resonance(NMR)method.Then,these three methods were comparatively analyzed based on the test results.Finally,it was proposed to optimize the key parameters of these three shale porosity test methods.And the following research results were obtained.First,in terms of the GIP method,the particle size of shale sample shall be in the range of 20-60 mesh and the helium saturation equilibrium time shall be over 1800 s.Second,in terms of the WIP method,the sample shall be dried for at least 48 hours under 110℃and saturated for 24 h under the confining pressure of 15 MPa.Third,in terms of the NMR method,NMR porosity calculation shall not be conducted until the NMR signal of the dried sample is deducted,on the basis of echo time and waiting time optimization.Fourth,porosity average and median value obtained by these three shale porosity test methods follow the relationship of WIP porosity>NMR porosity>particle GIP porosity>plunger GIP porosity.Fifth,different shale porosity test methods have greater influences on the calculation results of shale gas geological reserves,whose difference can reach 20%.In conclusion,during the application of NMR method and WIP method,fluid is introduced for saturation,which may damage the shale pores.However,the particle GIP porosity can reflect the entire space of shale more comprehensively and is not influenc

关 键 词：页岩气 储集层 孔隙度 气测法 液测法 核磁共振法 测试参数 储量计算精度 

分 类 号：P618.13[天文地球—矿床学]