砂岩热储温度场对回灌参数的响应机理与规律

Response Process and Mechanism of Sandstone Geothermal Reservoir Temperature to Reinjection Parameters

研究地热尾水回灌引起的热储层内温度场演化对地热资源的可持续利用具有重要意义.本文通过大型砂槽仿真试验模型的渗透试验、示踪试验和回灌试验结合数值模拟方法,研究了回灌参数与开采井热突破时间的定量关系,并通过非线性拟合和参数敏感性分析讨论了流体粘度与密度对高温流体向低温流体回灌结果的影响,以及回灌参数对开采井热突破时间的影响程度和内在机理与规律.结果显示回灌水在不同渗透率的砂岩层内运移速率不同,开采井热突破时间t分别与Q^(‒0.85)、ΔT^(‒0.21)和R^(1.4)呈线性关系.相关方程和分析结果表明,采灌温差ΔT在大于30℃时,其变化对开采井热突破时间t的影响已变得微弱,这是由于ΔT通过影响18.5℃等温线在温度过渡区内的相对位置来对开采井热突破时间t产生作用,而试验中采取的高温流体向低温流体回灌产生的误差可以引入粘度修正系数αμ修正.

The evolution of geo-temperature within the geothermal reservoir induced by reinjection of geothermal cooled water is of great importance for the sustainable utilization of geothermal resources.This study focuses on examining the quantitative relationship between reinjection parameters and the thermal breakthrough time of production wells.A simulation test using a large sand tank combined with numerical simulation methods was conducted.Permeation tests,tracer tests,and reinjection tests were performed in the simulation test model.Additionally,sensitivity analysis and nonlinear fitting were carried out to discuss the impact of fluid viscosity and density on reinjection results,as well as the degree of influence of reinjection parameters on the thermal breakthrough time of production wells and its underlying mechanisms and principles.The results show that the migration speed of reinjection water is different in sand reservoirs with different permeability,and the thermal breakthrough time t is linearly correlated with Q‒0.85,ΔT‒0.21,and R1.4.The correlation equation and analysis show that when the temperature difference between production and reinjection ΔT is more than 30℃,the influence of ΔT on the thermal breakthrough time of production well becomes weak,because ΔT exerts an effect on the thermal breakthrough time of production well t by influencing the relative position of the 18.5℃ is otherm in the temperature transition region,and the error for reinjection from high temperature fluid to low temperature fluid can be corrected by introducing the viscosity correction coefficient α_(μ).