应用核磁共振在线检测技术研究不同赋存状态下的页岩气动用规律  

Study on the production laws of shale gas in different occurrence states in the use of NMR online detection technology

作　　者：端祥刚[1,2] 胡志明 顾兆斌[1] 常进 沈瑞[1] 孙威[1] 穆英 周广照[3] DUAN Xianggang;HU Zhiming;GU Zhaobin;CHANG Jin;SHEN Rui;SUN Wei;MU Ying;ZHOU Guangzhao(PetroChina Research Institute of Petroleum Exploration&Development,Langfang,Hebei 065007,China;National Energy Shale Gas R&DCenter,Langfang,Hebei 065007,China;Department of Porous Flow&Fluid Mechanics,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国石油勘探开发研究院 [2]国家能源页岩气研发(实验)中心 [3]中国科学院大学渗流流体力学研究所

出　　处：《天然气工业》2021年第5期76-83,共8页Natural Gas Industry

基　　金：国家科技重大专项“页岩气渗流规律与气藏工程方法”(2017ZX05037-001);中国石油天然气股份有限公司直属院所基础研究和战略储备技术研究基金项目“页岩吸附气赋存机理及动用规律研究”(2018D-500807)。

摘　　要：要合理制订页岩气井生产制度,进而优化页岩气田开发技术政策,弄清不同赋存状态下的页岩气产出规律是前提和基础。为了避免间接测试的不确定性,研发了适用于高温高压条件下的核磁共振在线检测系统,选取四川盆地长宁地区N203井下志留统龙马溪组龙一_(1)^(1)层页岩岩心,以甲烷气体为实验流体,测量在页岩气开采过程中游离态和吸附态甲烷产出量的变化情况,并且结合页岩气衰竭式开发物理模拟实验,对不同赋存状态下的页岩气动用特征和产出变化规律进行了研究。研究结果表明:①饱和甲烷气体的页岩核磁共振T_(2)谱图具有明显的双峰特征,吸附态甲烷主要赋存于页岩纳米孔隙表面,弛豫时间较短(0.1~1.0 ms),而游离态甲烷则赋存于较大的页岩孔隙中,弛豫时间较长(1~100 ms);②采用核磁共振测量的甲烷总含气量及吸附态/游离态甲烷气量与采用间接方法计算的结果较为接近;③基于页岩气开发物理模拟实验,在开发初期,产出气以游离态甲烷为主,吸附态甲烷的阶段贡献率低于5%,随着生产的持续,吸附态甲烷的阶段贡献率逐渐增加,尤其是当压力低于15 MPa以后,吸附态甲烷的阶段贡献率迅速上升,至生产后期,吸附态甲烷的阶段贡献率超过50%,累计贡献率达到30%;④把实验结果换算为矿场条件下气井的生产动态数据,生产前5年,吸附气对气井累计产气量的贡献率不足5%,至生产末期,吸附气对累计产气量的贡献率可以达到25%。结论认为,核磁共振在线监测技术可以定量表征不同赋存状态下甲烷气体的动用规律,为后续开展页岩气气水两相渗吸、CO_(2)/CH_(4)吸附置换等研究提供了新的方法。The premise and basis to establish a reasonable shale gas well production system and then optimize shale gas field development technology policies is to understand the production laws of shale gas in different occurrence states.For the purpose of avoiding the uncertainty of indirect testing,a NMR(nuclear magnetic resonance)online detection system suitable for high temperature and high pressure conditions is developed.The cores of Long _(1)^(1) layer(the first submember of the first Member of Longmaxi Formation,Lower Silurian)taken through Well N203 in the Changning area of the Sichuan Basin were selected,and methane gas was used as the experimental fluid to measure the production changes of free and adsorbed methane in the process of shale gas exploitation.And combined with physical simulation experiment of shale-gas depletion development,the production characteristics and production change laws of shale gas in different occurrence states were studied.And the following research results were obtained.First,the NMR T_(2) spectrum of the methane saturated shale has obvious characteristics of two peaks.The adsorbed methane mainly occurs on the surface of shale nanopores and the relaxation time is shorter(0.1-1.0 ms),while the free methane occurs in the larger pores and the relaxation time is longer(1-100 ms).Second,the total methane content and adsorbed/free methane content measured by NMR are closer to the results obtained by the indirect method.Third,the physical simulation experiment of shale gas development shows that in the early stage of the development,the produced gas is dominated by free methane and the stage contribution rate of adsorbed methane is less than 5%.As the production continues,the stage contribution rate of adsorbed methane gradually increases.And especially when the pressure is lower than 15 MPa,the stage contribution rate of adsorbed methane rises rapidly.In the late stage of the development,the stage contribution rate of adsorbed methane exceeds 50%and its cumulative contribution rate reaches

关 键 词：核磁共振 页岩气 甲烷 吸附态 游离态 弛豫时间 产气规律 T_(2)谱 

分 类 号：TE37[石油与天然气工程—油气田开发工程]