Numerical simulation of enhancing shale gas recovery using electrical resistance heating method

摘要

Gas production from shale gas reservoirs can be enhanced by increasing the temperature of the reservoirs due to the increased desorption of the adsorbed gas. However, limited techniques are currently available for practically introducing heat into such low permeability reservoirs. This paper investigates the feasibility of an electrical resistance heating method to promote shale gas production by increasing the temperature of the reservoirs. To achieve our research goal, a mechanistic numerical model is developed to describe electrical field, temperature field, and pressure field. To capture gas flow in a shale gas reservoir, non-linear flow, diffusion and adsorption/desorption which are all dependent on temperature are incorporated into a dual continuum media model. In our study, the gas production enhancement by electrical heating with two parallel horizontal electrode wells is evaluated using this model. We then assess impacts of the thermal properties of the formation, electrode length, electrical power, Langmuir volume and starting time of heating on gas production. The results indicate that the electrical heating method using two parallel horizontal electrodes can be an efficient method to enhance shale gas production. The heat capacity and conductivity of the formation have significant impacts on gas production. Reservoirs with low conductivity and low heat capacity tend to produce more gas due to heating. Meanwhile, shale gas reservoirs with high Langmuir volume also tend to yield more gas due to heating for. To maximize gas production, electrical power should be optimized based on the properties of shale gas reservoir and heating equipment. Longer electrodes heat more formations of the reservoir and thus lead to higher gas production by using the electrical heating method. In order to efficiently enhance shale gas production, electrical heating should start later in gas production, instead of earlier. (C) 2018 Elsevier Ltd. All rights reserved.