Effect of fracture distribution and well spacing on heat recovery performance of enhanced geothermal system
The mining of medium-high temperature rock-heat reservoirs belongs to the enhanced geothermal system.The mining method is mainly realized by reinjection wells,production wells and fractured reservoirs.The layout of well spacing and fracture parameters will directly affect the flow path of fluid,and then affect the recharge amount and heat exchange efficiency.Therefore,we consider the study of the influence of the combination of fracture parameters and well spacing on the heat recovery performance,and select the most favorable combination parameters of fracture distribution and well spacing for production,so as to provide fracture network target for artificial storage and well spacing reference for well layout design.In this study,TOUGH2 software was used to establish a multi-field coupling model of water and heat.Sixteen sets of different fracture parameter combinations were set up in the reservoir,and 48 sets of experimental simulations were carried out.The influence of different fracture parameter combinations on heat recovery performance under the condition of 200 m,300 m and 500 m well spacing for 30 years is analyzed.The results show that the reservoir and heat recovery temperature are greatly affected by well spacing,and the reservoir pressure is greatly affected by fracture parameters.Under the condition of different fracture parameter combinations,the temperature of production wells with 200 m well spacing for 30 years decreased from 81 ℃ to 47 ℃,the temperature of production wells with 300 m well spacing for 30 years decreased to 55℃,and the temperature of production wells with 500 m well spacing for 30 years decreased to 67 ℃.The reservoir pressure varies greatly under different fracture parameters.The maximum increases from the initial 24 MPa to 98 MPa,and the minimum increases to 28 MPa.According to the simulation results,we get the best combination of fracturing parameters for 80 m thick reservoir:well spacing 500 m,fracture opening 0.8e-4～0.9e-4 m,fracture number between 10～15,fracture spacing 10 m.The results of this study can be applied to the development of EGS,which can provide guidance for the efficient fracturing of medium-high temperature and low permeability reservoirs,improve the heat recovery efficiency and prolong the service life of the system.
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