Numerical analysis of characteristics of reaction in hydrothermal jet drilling for geothermal energy

Hydrothermal jet technology is a drilling method, which is potentially suitable for the exploitation of geothermal energy in deep hard formations. The generation of a stable hydrothermal jet via combustion in the reaction chamber is an important subject for successful applications. In this paper, the Peng-Robinson equation of state and four combustion models are applied to simulate the reaction in the downhole chamber. Simulation results are compared with experimental data to obtain a suitable model. The reaction flow field and effects of several factors (i.e., fuel and oxygen flow rate, mass fraction, and wall temperature) are studied. Results show that under the conditions of this paper, the finite rate model is more suitable. It may be better to inject the maximum fraction of fuel for complete reaction to obtain the highest jet pressure and temperature simultaneously. The cooling water flow rate and temperature can be adjusted over a broad range to control the temperature of the reaction chamber within a suitable range. Results in this paper could provide guidance for further research on hydrothermal jet drilling.