Geothermal Drilling Selection And Parameter Optimization Design

As a kind of clean and environmentally friendly energy,geothermal energy has been paid more and more attention and application.At present,the development and utilization of geothermal energy at home and abroad is still dominated by drilling.Based on the systematic investigation of geothermal well types at home and abroad,the geothermal well types are divided into single well system and multi-well system according to the number of wellbores.According to whether the fluid in the wellbore enters the formation,it is divided into open-loop system and closed-loop system,and analyzed.Features of various well types and systems.This paper mainly studies the closed-loop system in which the fluid in the wellbore does not enter the formation and has no interference to the formation.In this paper,a single well system,a U-type butt well system and a multi-shot geothermal well system are combined with heat transfer theory.A one-dimensional steady heat transfer model of geothermal wellbore is established.According to the model,any wellbore can be calculated.The temperature of the fluid at the location and the amount of heat exchange;the cost quotas of the three well types were investigated,and their respective payback periods were compared.The recovery period of the single well system was 22 years,and the payback period of the U-well was 18 years.The recovery period of the well is 11 years.According to the system payback period,it is concluded that the multi-production well type is superior to the U-type well system and the single-well system.It can be used as a reference in practical engineering applications,and different well type combinations can also be adopted.The numerical simulation software ANSYS was used to simulate the heat transfer process of the U-shaped well,and the geometric model of the U-shaped well was established.By comparing the simulated wellbore temperature curve with the mathematical model,the results show that the maximum error of the outlet water temperature in the injection well is 4.24%,and the horizontal curve is basically consistent,indicating that the established mathematical model is reliable,on the temperature distribution cloud.The specific change process of the fluid temperature in the wellbore and the surrounding formation temperature can be visually displayed.Finally,the outlet water temperature and heat transfer of the wellbore were simulated by the established models under different injection flow rates,wellbore diameters,horizontal section lengths and geothermal gradients.The simulation results show that when the diameter of the wellbore is constant,the higher the injection flow rate,the lower the outlet water temperature,and the higher the heat exchange amount.In order to ensure the maximum water exchange temperature while the outlet water temperature is high,the injection fluid flow rate should be between 0.5-1 m/s.Under the condition of constant flow rate,the larger the diameter of the wellbore,the lower the outlet water temperature and the higher the heat exchange capacity.In order to ensure the maximum water exchange temperature while the outlet water temperature is high,the diameter of the wellbore is about 200mm;the horizontal wellbore is increased by 400 m.The outlet water temperature increases by 7 ?;for every 2 ? increase in the geothermal gradient,the outlet water temperature increases by 5 ?.