Three-dimensional numerical simulation of enhancing shale gas desorption by electrical heating with horizontal wells

Increasing temperature can significantly enhance gas desorption and hence improves gas production in shale gas reservoirs, but there are limited practical techniques that can be used to introduce heat into such low permeability reservoirs. This paper investigates the feasibility of an electrical heating method for shale gas desorption enhancement with a mechanistic numerical model. The model incorporated the mechanisms of shale gas adsorption/desorption as a function of low-frequency conduction heating. We evaluate the gas desorption efficiency of heating by two parallel horizontal electrode wells using this model. The electrodes are placed in the two parallel horizontal wells. The impact of the physical properties of formation, electrode length and distance between electrodes, electrical power, and Langmuir volume on gas desorption are investigated. The results indicate that electrical heating using two parallel horizontal electrodes can be an efficient method to enhance shale gas desorption. The temperature and gas desorption increase when the two horizontal electrodes get closer. However, the electrode length and formation resistivity have insignificant impact on gas desorption as long as the injected electrical power is maintained constant. The reservoir thermal properties (heat capacity and conductivity) have a significant impact on gas desorption. Reservoirs with low conductivity and heat capacity get more benefit from the method. The amount of desorbed gas is proportional to the Langmuir volume, so electrical heating method is more applicable to the shale gas reservoir with high Langmuir volume. Gas desorption is directly proportional to the electrical power, therefore, high enough electrical power is required to make the technique successful.