Effect of underground seepage field on heat extraction performance of coaxial casing in middle-deep horizontal wells
To improve the heat extraction efficiency of middle-deep geothermal wells,a horizontal well coaxial casing heat exchanger is designed.The influence of factors such as seepage velocity,seepage direction,and length of horizontal segment on the heat extraction performance of the coaxial casing heat exchanger in horizontal wells is studied considering the effect of underground seepage field.The results show that the outlet temperature and heat extraction power of the horizontal well coaxial casing heat exchanger are 12.6％and 42.9％higher than that of the traditional coaxial casing heat exchanger.Under the intermittent mining condition,the decrease in outlet temperature of the heating system is relatively small,and the formation temperature recovery is better.When the seepage velocity of the aquifer is greater than 5×10-8 m/s,the outlet temperature of the system is higher than that without an aquifer.Too low seepage velocity is not conducive to the heat extraction performance of geothermal wells.The seepage direction perpendicular to the horizontal segment has a stronger effect on improving the heat extraction performance of the system than that in the same direction as the horizontal section.Increasing the injection flow rate,decreasing the injection temperature,and increasing the length of the horizontal segment can effectively improve the heat extraction performance of geothermal wells.
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