松辽盆地增强型地热系统(EGS)地热能开发热-水动力耦合过程

Coupled Thermal-Hydrodynamic Processes for Geothermal Energy Exploitation in Enhanced Geothermal System at Songliao Basin,China

增强型地热系统地热能开发涉及到热和水动力的耦合,对应的温度和压力场时空变化特征是评价地热开发效果的关键问题。基于松辽盆地徐家围子深部地质条件,采用TOUGH2进行了地热能开发过程中裂隙-孔隙介质系统中温度和压力变化的数值模拟,分析了不同埋深水平情况下地热能开发的差别,研究了孔隙基质和裂隙介质的渗透率和孔隙度、岩石导热系数、井径、注入压力、注入温度及裂隙周围基质因素对地热能开发的影响。结果表明:采用定压力开发时生产井抽出控制整个区域的压力分布,压力梯度在注入井区域较大,并随着开发的进行,注入井的注入对压力的影响逐渐增大;温度由注入井到生产井逐渐增大,并随着开发的进行温度降低范围逐渐向生产井扩大;质量和热提取速率随时间逐渐减小。不同埋深位置的模拟结果显示,埋深大的温度相对较高,水的流动性较强,质量和热提取速率较高,压力和温度变化幅度均较大。裂隙系统的渗透率、注入井/生产井压力和注入温度、井径对深部地热开采过程中的压力和温度影响较大,从而影响热的提取效率;而孔隙基质的渗透率和孔隙度、裂隙介质的裂隙度和岩石的热传导系数的影响并不明显。

The geothermal energy exploitation in enhanced geothermal system involves the coupled processes of temperature and pressure,the spatial and temporal variation of which is the key issue.Based on the deep geological condition of Xujiaweizi in Songliao basin,using the TOUGH2 software,we simulate the variation of temperature and pressure in fracture-matrix media system,analyze thedifference of geothermal development in different depth levels,and study the effects of important factors including the permeability and porosity of porous and fractured media,rock thermal conductivity,well radius,injection pressure and temperature,and surrounding matrix.The results show the pressure distribution is dominated by production well with large pressure gradient at the injection well and the impact of injection well increases with time.Temperature increases from injection well to production well and the area of decrease of temperature increases as the development of geothermal.Mass and heat extraction rate reduce and stabilize with time.The simulation results of different depth levels indicate the great mass and heat extraction rate and large change of pressure and temperature exist in the big depth level because of large water mobility.The effects of factors including fractured media permeability,injection/production well pressure and temperature,and well radius on pressure and temperature of the system are great,and ultimately it affects heat extraction efficiency.While the effects of another factors are not obvious.