CO2羽流地热系统开采特性数值模拟及预测模型

Numerical simulation and predictive model of mining characteristics of CO2 plume geothermal system

为了研究超临界CO2羽流地热系统的采热特性,建立了耦合井筒储层的数学模型,同时考虑井筒对流动的影响以及岩层的热量补偿作用,通过T2Well/ECO2N软件分析了开采周期内产出流量、热储层压力和温度随时间的变化情况,并以数值计算为基础建立了开采特性预测模型.结果表明:CO2产量在开采初期较小,连续注采10年后流量可达稳定状态,在羽流地热产出CO2时即存在热虹吸效应,出口井温度30年内基本保持恒定;通过单因素分析,研究注入参数对开采特性的影响,其中CO2注入流量对注入井口压力、出口井温度、出口井流量都有显著影响,井间距主要影响出口井温度和出口井压力;基于响应曲面法建立的开采特性预测模型可以更加直观地反映参数对开采特性的耦合影响,并可为地热发电系统的优化设计提供依据.

A fully coupled wellbore and reservoir model of the CO2 plume geothermal system was built for studying the characteristics of geothermal heat extraction using CO2 captured from the fossil-fired power plant,and the effects of the wellbore on flow and the thermal compensation of the rock layer are considered.The T2Well/ECO2N software was used to numerically simulate the changes of temperature,pressure and mass flow rate profiles of the geothermal heat mining system over time.Based on the numerical simulation results,a mining characteristic prediction model was developed.The results show that the initial production of CO2 is relatively small,and the flow rate can reach a steady state after 10 years of continuous injection and production.The thermosiphon effect occurs with CO2 production,and the outlet well temperature remains basically constant within 30 years.The wellhead temperature of the production well remains constant for 30 years.The single factor analysis was performed to study the influence degree of each influencing factor on the mining index.The CO2 injection flow rate has great influence on the injection wellhead pressure,the production wellhead temperature and flow rate.The distance between the injection well and the production well significantly affects the production wellhead temperature and pressure.The response surface method was used to create the characteristic prediction model,which can reflect the coupling effects of parameters on mining characteristics more intuitively.In addition,the mining characteristic prediction model can provide a basis for the optimization design for geothermal power generation systems.