孔隙—裂缝型岩溶热储热—流—化多场耦合作用机理OA北大核心CSTPCDEI
Thermal-hydraulic-chemical coupling mechanism of porous-fractured karst geothermal reservoirs
岩溶型热储开采过程中,储层孔隙内水岩反应会导致流动通道变形,忽略这一反应过程将导致热储产能预测偏差较大.为了揭示水岩作用下岩溶型热储孔隙和裂缝形态的演化特征,综合考虑了孔隙和裂缝内的水岩反应过程,搭建了孔隙—裂缝双重介质热—流—化多场耦合模型并验证了其准确性,进而分析了热—流—化多物理场与孔隙—裂缝形态的分布特征,探究了孔隙—裂缝内水岩反应对孔、缝变形和系统取热性能的影响.研究结果表明:①欠饱和注入条件下,注入井处发生溶解反应,生产30年时,裂缝开度增大了 0.32％,孔隙度增大了 75.76％;②生产30年时,考虑孔隙—裂缝内水岩反应案例的裂缝平均开度降低了 0.05％,考虑裂缝而不考虑孔隙内水岩反应案例的裂缝平均开度增大了 17.12％,二者呈现相反的变化趋势;③考虑孔隙—裂缝内水岩反应案例相比于仅考虑裂缝而不考虑孔隙内水岩反应的案例,生产30年时,生产温度相差不大,系统注采压差增大了 1.57倍.结论认为:①岩溶型热储孔隙内水岩反应对孔、缝变形和取热性能影响显著,其改变了水岩反应对裂缝开度的作用机理,影响系统注采压差;②孔隙内的水岩反应不容忽视,在进行岩溶型热储产能的精确预测和经济评价时必须予以充分考虑:③该认识可为岩溶型热储开发方案设计和产能预测方面提供理论和技术参考.
Water-rock reactions in karst thermal reservoirs during exploitation may lead to deformation of flow pathways.Neglecting this reaction will yield a large deviation in predicted productivity of geothermal reservoirs.A(pore-fracture)two-medium thermal-hydraulic-chemical coupling model was developed to reveal the evolution of the pore-fracture morphology in karst geothermal reservoirs under water-rock reaction,and it was verified.With this model,the distribution characteristics of multi-physics(thermal-hydraulic-chemical)field and pore-fracture morphology are analyzed,and the influences of water-rock reaction on the pore/fracture deformation and system thermal performance are identified.The following results are obtained.First,dissolution reaction occurs at the injection well under the condition of under-saturated injection.The fracture aperture increases by 0.32％and the porosity increases by 75.76％after 30 years.Second,after 30 years of production,the average fracture aperture in the case of considering water-rock reactions in both pores and fractures decreases by 0.05％,and that in the case of only considering water-rock reactions in fractures increases by 17.12％,showing the opposite trend.Third,after 30 years of production,the production temperature in the case of considering water-rock reactions in both pores and fractures is similar to that in the case of only considering water-rock reactions in fractures,but the injection-production pressure difference increases by 1.57 times.In conclusion,for karst geothermal reservoirs,the water-rock reaction in pores has great influences on pore/fracture deformation and system thermal performance,and it changes the mechanism at which the water-rock reaction acts on the fracture aperture and affects the system's injection-production pressure difference.Thus,the water-rock reaction in pores should not be ignored,but should be fully considered in accurate productivity prediction and economical evaluation of karst geothermal reservoirs.This understanding provides a theoretical and technical support for the development planning and productivity prediction of karst geothermal reservoirs.
姬佳炎;宋先知;李根生
中国石油大学(北京)石油工程学院中国石油大学(北京)石油工程学院||油气资源与工程全国重点实验室·中国石油大学(北京)
地球科学
岩溶型热储孔隙结构裂缝开度水岩作用取热性能孔—缝双重介质热—流—化多场耦合裂缝变形
Karst geothermal reservoirPore structureFracture apertureWater-rock reactionThermal performancePore-fracture two-mediumThermal-hydraulic-chemical couplingFracture deformation
《天然气工业》 2024 (003)
214-224 / 11
国家自然科学基金重大项目"高温岩石动态损伤机理与高效破碎方法"(编号:52192624)、国家自然科学基金国家杰出青年科学基金项目"油气井流体力学与工程"(编号:52125401).
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