Performance of Fractured Geothermal Reservoirs: Utilizing Water Jet Drilled Laterals

Abstract

Utilizing the Radial Jet Drilling (RJD) technology in the existing geothermal wells has been considered recently for improving the productivity or injectivity of the wells. In this study, the application of RJD in naturally fractured reservoirs with an injection well and a production well is explored using a coupled THM three-dimensional DFM (discrete fracture-matrix) model. To this end, several cases of fracture models with different fracture spacing are employed to explore the impact of the RJDs on the performance of the geothermal doublet. Results show that for most cases, the required pressure differences are decreased due to the application of RJD laterals. We also observe that the produced temperature is affected by the application of RJD in high and low fracture spacing. The observed adverse effect on the high fracture spacing cases can be attributed to linking the producer well to fractures between both wells by the RJD laterals. On the other hand, the favorable impact on the produced temperature observed in the low fracture spacing case is due to connecting the wells to the fractures outside the area between the wells. Different key performance indicators are considered for featuring the conditions under which the application of RJD is favorable. By comparing different injection rate, fracture spacing, and rock matrix permeability, we find that in order to gain the best performance of RJD it is important to direct RJD laterals in the direction outside the area between the wells aiming at increasing the effective volume of the reservoir.