基于热——流—固耦合的多分支径向井地热开发模型及其取热效果分析  

Geothermal development model of multilateral radial well and its heat extraction effect analysis based on thermal-hydraulic-mechanical coupling

作　　者：王天宇[1] 周小夏 李根生[1] 王元[2] 田守嶒[1] WANG Tianyu;ZHOU Xiaoxia;LI Gensheng;WANG Yuan;TIAN Shouceng(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;Engineering Research Center of Geothermal Resources Development Technology and Equipment,Ministry of Education,Changchun,Jilin 130026,China)

机构地区：[1]油气资源与探测国家重点实验室·中国石油大学(北京) [2]地热资源开发技术与装备教育部工程研究中心

出　　处：《天然气工业》2023年第3期133-144,共12页Natural Gas Industry

基　　金：国家自然科学基金重大项目“高温岩体复杂缝网造储理论与技术”(编号:52192621);地热资源开发技术与装备教育部工程研究中心开放课题“多分支径向井开采干热岩数值模拟研究”(编号:21018);中国石油大学(北京)科研基金项目“干热岩柔性压裂裂缝起裂机理研究”(编号:2462022QZDX006)。

摘　　要：多分支径向井地热开发取热系统是开采地热资源的一种新方法,具有单井注采一体、换热面积大、沟通能力强等优势,其中布井参数和储层条件是影响其取热效果的关键因素。为此,建立了基于热—流—固多物理场耦合的单主井筒多分支径向井传热模型并验证了模型的准确性,对比了直井与多分支径向井的取热效果,研究了布井参数、天然裂缝缝长等因素对系统取热效果的影响。研究结果表明:(1)在取热过程中岩石发生收缩变形,裂缝渗透率显著提高,但促进了冷锋入侵现象,进而加剧了热突破,缩短了系统的取热寿命;(2)增加分支井数量,可增大水平方向的取热区域,沟通更多天然裂缝,保持较高的取热温度和取热功率,其中6分支井为最优井数,最优取热总量为7.37×10^(15) J;(3)分支径向井越长,储层降温越慢,平均每增加1 m,生产温度升高0.16℃;(4)增大井间距,能延缓热突破,提高系统取热效率,延长高温取热时间,最优井间距为350 m,年取热功率为8.28 MW;(5)系统取热功率随着天然裂缝缝长的增加而降低。结论认为:(1)相较于直井,多分支径向井能沟通更大体积的高温储层,能获得较高的取热功率和取热总量,在30年取热时间里,热储采出程度增加了8.72%,有利于提高地热系统的经济效益;(2)岩石形变对取热系统有着重要影响,在进行取热效果模拟及经济性评价时必须予以充分考虑。The multilateral radial well geothermal development and extraction system is a new method for exploiting geothermal resources,which has the advantages of integrated single-well injection and production,large heat exchange area and strong communication ability.Well layout parameters and reservoir conditions are the key factors affecting the heat extraction effect of the system.In this paper,a heat transfer model of multilateral radial well with a single main hole based on thermal-hydraulic-mechanical coupling is established,and its accuracy is verified.The heat extraction effect of a multilateral radial well is compared with that of a vertical well,and the influences of well layout parameters and natural fracture length on the heat extraction effect of the system are studied.And the following research results are obtained.First,the thermal-hydraulic-mechanical coupling model shows that in the process of heat extraction,rocks undergo shrinkage deformation and fracture permeability increases significantly,but it promotes the invasion of cold front,which further intensifies the thermal breakthrough and shortens the heat extraction life of the system.Second,increasing the number of branch holes can enlarge the heat extraction area in the horizontal direction and communicate more natural fractures,so as to keep higher heat extraction temperature and power.Among them,six branch holes is the optimal well layout number,and the optimal total heat extraction is 7.37×10^(15)J.Third,the longer the lateral radial hole is,the slower the reservoir temperature drops.The production temperature increases by 0.16℃as the average length is increased by 1 m.Fourth,increasing well spacing can slow down the thermal breakthrough,improve the heat extraction efficiency and extend the high-temperature heat extraction time.The optimal well spacing is 350 m,and the corresponding annual heat extraction power is 8.28 MW.Fifth,the heat extraction power of the system decreases with the increase of the natural fracture length.In conclusion,compa

关 键 词：干热岩 热—流—固耦合 多分支径向井 布井参数 天然裂缝 热应力 取热功率 参数分析 

分 类 号：TK529[动力工程及工程热物理—热能工程]