深层页岩气产出过程碳同位素分馏特征及其地质意义——以川南地区泸州区块奥陶系五峰组-志留系龙马溪组为例  

Characteristics and geological implications of carbon isotope fractionation during deep shale gas production:A case study of the Ordovician Wufeng Formation-Silurian Longmaxi Formation in the Luzhou Block of Southern Sichuan Basin

作　　者：赵圣贤 杨学锋 刘永旸 卢双舫 刘文平[5] 李博[1,2] 张鉴 李文镖 张小涛 赵文韬 黄山 王峻 ZHAO Shengxian;YANG Xuefeng;LIU Yongyang;LU Shuangfang;LIU Wenping;LI Bo;ZHANG Jian;LI Wenbiao;ZHANG Xiaotao;ZHAO Wentao;HUANG Shan;WANG Jun(Shale Gas Research Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610051,China;Sichuan Key Laboratory of Shale Gas Evaluation and Exploitation,Chengdu,Sichuan 610213,China;School of Geosciences,China University of Petroleum(East China),Qingdao,Shandong 266580,China;Sanya Offshore Oil&Gas Research Institute,Northeast Petroleum University,Sanya,Hainan 572025,China;PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610051,China;Sichuan Shale Gas Exploration and Development Co.,Ltd.,Chengdu,Sichuan 610017,China;Shunan Division,PetroChina Southwest Oil&Gasfield Company,Luzhou,Sichuan 646000,China)

机构地区：[1]中国石油西南油气田公司页岩气研究院 [2]页岩气评价与开采·四川省重点实验室 [3]中国石油大学(华东)地球科学与技术学院 [4]东北石油大学三亚海洋油气研究院 [5]中国石油西南油气田公司 [6]四川页岩气勘探开发有限责任公司 [7]中国石油西南油气田公司蜀南气矿

出　　处：《天然气工业》2024年第8期72-84,共13页Natural Gas Industry

基　　金：国家自然科学基金项目“页岩气井生产过程中的甲烷碳同位素分馏机理、表征及应用”(编号:42302170);中国石油攻关性应用性科技专项“页岩气规模增储上产与勘探开发技术研究”(编号:2023ZZ21)。

摘　　要：四川盆地南部地区(以下简称川南地区)中浅层页岩气已实现规模效益开发,深层页岩气是当前和将来一段时间增储上产的重要领域。为了探索川南地区深层页岩气中碳同位素分馏影响因素及其地质意义,以川南地区泸州区块深层奥陶系五峰组—志留系龙马溪组页岩为研究对象,系统开展了12块岩心现场解析测试和2口生产井连续监测工作,分析了甲烷、乙烷碳同位素(δ^(13)C_(1)、δ^(13)C_(2))分馏机理,建立了同位素分馏模式,并构建了根据同位素分馏参数计算吸附气与游离气相对比例和EUR的数学模型和方法,最后分析了页岩气赋存状态、富集特征和流动产出规律。研究结果表明:①川南地区深层页岩气解析过程中δ^(13)C_(1)值变重幅度介于10.3‰~22.7‰,δ^(13)C_(2)值变重幅度最大仅为4.2‰,页岩气井生产过程中甲烷和乙烷均存在约8‰的碳同位素分馏幅度;②页岩气完整产出过程中碳同位素分馏普遍存在“稳定—变轻—变重—再变轻”的4阶段模式,装罐后解析气仅能观测到基质产气为主所对应的变重阶段,而生产井井口气能够观测到反映裂缝与基质共同产气所对应的变轻阶段,环境温度和压力变化均会改变原有天然气碳同位素分馏模式,影响程度与所处阶段密切相关;③生产初期井口气样相较于岩心解析气样和生产中—后期井口气样更能反映储层原始天然气碳同位素组成信息;④通过构建多尺度多机理耦合的天然气碳同位素分馏模型,能够准确计算深层页岩原位含气量、吸附气/游离气比例等关键参数,实现页岩气井EUR预测和生产过程中吸附气/游离气产出比例的有效评价。结论认为,开展页岩气产出过程中碳同位素分馏影响因素及机理分析,可为深层页岩气赋存状态、富集特征和流动产出规律提供全新的视角和技术手段,将有助于深层页岩气的效益开发。The medium-shallow shale gas in the southern part of the Sichuan Basin(hereinafter referred to as Southern Sichuan Basin)has been efficiently developed in a large scale.Deep shale gas is an important field for reserves and production increase at present and in the future.In order to explore the influential factors and geological implications of the carbon isotope fractionation in the deep shale gas in the Southern Sichuan Basin,this paper systematically conducts an on-site desorption test of 12 cores and continuous monitoring of 2 production wells with the deep Ordovician Wufeng Formation–Silurian Longmaxi Formation shale in the Luzhou Block of Southern Sichuan Basin as the research object.Then,the carbon isotope(δ^(13)C_(1)andδ^(13)C_(2))fractionation mechanisms of methane and ethane are analyzed,and the isotope fractionation models are established.In addition,the mathematical model and method to calculate adsorbed/free gas ratio and EUR on the basis of isotope fractionation parameters are established.Finally,it is recommended to support the analysis of the occurrence state,enrichment characteristics and flow and production patterns of shale gas.And the following research results are obtained.First,in the desorption process of deep shale gas in the Southern Sichuan Basin,theδ^(13)C_(1)values increase by 10.3‰to 22.7‰,and theδ^(13)C_(2)values increase by a maximum of only 4.2‰.In the process of shale gas well production,both methane and ethane exhibit a carbon isotope fractionation amplitude of approximately 8‰.Second,the complete process of shale gas production universally exhibits a four-stage isotope fractionation pattern characterized by"stable-lighterheavier-lighter again".The desorbed gas in a canister only shows a heavier stage corresponding to matrix dominated gas production.The wellhead gas of production well shows a lighter stage corresponding the combined gas production from fractures and matrix.Changes in either ambient temperature or pressure can modify the original isotope fractionatio

关 键 词：四川盆地 深层页岩气 同位素分馏 原位含气量 吸附气/游离气比例 EUR预测 

分 类 号：TE122[石油与天然气工程—油气勘探] TE312