羊八井热田生产井监测及变化影响分析

Analysis of Production Wells Monitoring and Its Impacts in Yangbajing Geothermal Field

羊八井热田是我国开发最早、最成功的高温地热田,目前尚有较大的地热资源开发潜力.热田在第四系半地堑式断陷内,发育有两组不同方向的断裂,构成了热田流体运移的主要通道.深部高温流体由北区F2断裂处上涌后沿断裂带向南区运移,形成了羊八井热田浅层砂砾岩和风化壳热储以及北区深部花岗岩型热储.从2000年开始对热田井口温度和压力开展了常态化监测,并在2015年增加了热田井内水位监测和热水湖水位观察工作.通过分析热田不同构造位置典型生产井的温度、压力、水位变化情况以及受不同时期回灌、停机养汽的影响,结合热水湖等自然景观水位的变化,认为羊八井热田南区尾水回灌产生的压力升高有助于阻碍北区高温流体向南的快速流动,再结合2015年开始的北区3001井回灌和停机养汽活动,使得热田北区浅层热储的温度和压力得到了较好的恢复,并具有较好的一致性.热田回灌和停机养汽活动可有效恢复和维持热田水位,水位上升幅度最大可达15m.井口温度、压力和水位监测成果能够有效地反映出热田热储的变化情况,采灌平衡对热田可持续开发评价具有重要的实用价值.

Yangbajing geothermal field is the earliest and most successful one in China,which has great potential of the geothermal reso urces.Two groups of fractures in various directions were developed in the half-graben type fault in Quaternary system,which are the main channel of fluid migration in the geothermal field.The deep high heat fluid migrates into the south area along the fracture belt after upwelling from F2 fracture in the north area,which forms shallow geothermal reservoir with glutenite and weathering crust and deep geothermal granitoid reservoir in the north area.Wellhead temperature and pressure has been monitored usually in the geothermal field since 2000 and water level in wells was monitored and hot lake level was observed since 2015.Changes of well temperature,pressure and the water level of typical production wells with different structure in the geothermal field were analyzed.Recirculation and shutting down were done at various stages.The water level change of the hot lake and other natural landscapes was considered,and the increased pressure caused by tailwater recirculation in the south area may prevent quick flow of the hot fluid from the north area.After the recirculation and shutting down for recovering in Well 3001 of the north area since 2015,the temperature and pressure in the shallow geothermal reservoirs in the north area were recov-ered.The water level of the geothermal field will restore and maintain after the recirculation and shutting down with the maximum raise of 15 m.Therefore,the monitoring results of the wellhead temperature,pressure and water level can effectively reflect geothermal reservoir status and production-injection equ ilibrium of the geothermal water is necessary for evaluating sustainable development and utilizing of the geothermal field.