多分支井增强型地热开发系统设计及产能评价  

Design and productivity evaluation of multi-lateral well enhanced geothermal development system

作　　者：张杰[1,2] 谢经轩[3] ZHANG Jie;XIE Jingxuan(School of Mechatronic Engineering,Southwest Petroleum University,Chengdu,Sichuan 610500,China;Geothermal Energy Research Center,Southwest Petroleum University,Chengdu,Sichuan 610500,China;School of Mechanical Engineering,Tianjin University,Tianjin 300072,China)

机构地区：[1]西南石油大学机电工程学院 [2]西南石油大学地热能研究中心 [3]天津大学机械工程学院

出　　处：《天然气工业》2021年第3期179-188,共10页Natural Gas Industry

基　　金：四川省科技计划项目“干热岩地热资源开发方案设计及热流固耦合机理研究”(编号:2020JDRC0088);西南石油大学过程装备力学与安全评价青年科技创新团队项目(编号:2018CXTD12)。

摘　　要：增强型地热开发系统作为开发干热岩地热资源的一种有效手段,其合理的结构设计对于实现干热岩的有效开采至关重要。为此,基于传统的双井开发模型,设计出了一种多分支井增强型地热开发系统(包含1个低渗透性热储、3口注入分支井、3口生产分支井和3条人工裂隙),采用局部热平衡法建立了三维水热耦合数值评价模型,通过裂隙流传热Lauwerier解析理论验证了该模型的精确性和可靠性;进而基于热采过程中储层内部水岩耦合机制,探究了储层参数、布井参数和注采参数对该开发系统产热性能的影响。研究结果表明:①多分支井开发系统裂隙中的冷锋“侵岩效应”比岩体基质中更强,增大储层渗透率虽然可以提高内部换热效果,但也增强了冷锋侵透性;②系统年取热量随运行时间推移而逐渐降低、随注入温度升高而降低、在运行前期随储层渗透率增大而增大,但当热突破完成后其值下降明显;③系统热提取率、生产质量流率受储层孔隙度、注入温度的影响较小,但随注采井垂距的增大而降低;④生产温度随储层渗透率的增大而下降幅度较大、随储层孔隙度的增加而升高,但随注采井垂距的降低而降低;⑤增加生产井长度可以提高前期运行系统的产热性能,提高注采压差在一定程度上可以增强系统的采热能力,但过高的压差会严重影响储层的使用寿命。Enhanced geothermal development system is an effective means to develop hot dry rock geothermal resources,and its reasonable structural design is crucial to the efficient exploitation of hot dry rocks.In this paper,a multi-lateral well enhanced geothermal development system,which is composed of one low-permeability thermal reservoir,three multi-lateral injection wells,three multi-lateral production wells and three artificial fractures,was designed based on the traditional dual-well development model.Then,a 3D hydro-thermal coupling numerical evaluation model was established by using the local heat balance method,and its accuracy and reliability were verified according to Lauwerier analytical theory of fractured flow and heat transfer.Finally,the influence of reservoir parameters,well layout parameters,and injection-production parameters on the heat production performance of this enhanced geothermal development system were explored based on the water-rock coupling mechanism inside the reservoir in the process of thermal production.And the following research results were obtained.First,the"rock invasion effect"of the cold front in the fractures of the multi-lateral well development system is stronger than that in the matrix.Increasing the reservoir permeability can improve the internal heat transfer effect,but also enhances the"invasion performance"of cold front.Second,the annual thermal energy extraction of the system gradually decreases over time and it also decreases with the increase of the injection temperature.It increases with the increase of the reservoir permeability in the early stage of the operation,but decreases greatly after the completion of the thermal breakthrough.Third,the system's thermal energy extraction rate and production mass flow rate are less influenced by reservoir porosity and injection temperature,but they decrease with the increase of the vertical spacing of injection-production wells.Fourth,the production temperature decreases greatly with the increase of the reservoir permeability,in

关 键 词：干热岩 增强型地热系统 多分支井 布井方法 局部热平衡法 水热耦合 产能评估 参数分析 

分 类 号：P314[天文地球—固体地球物理学] TK529[天文地球—地球物理学]