Volume 64

Multi-physics simulation of fracture evolution under wind-solar fluctuation energy supply with oil shale electric heating-thermal steam synergy Xu Lou, Jing Wang, Huiqing Liu

Abstract

Oil shale has abundant reserves and is an important alternative resource for traditional oil and natural gas. In situ mining is the most promising method for oil shale, which mainly includes electric heating and steam injection heating methods. However, both methods have obvious drawbacks. Electric heating methods typically require huge amounts of electricity consumption, while steam injection results in significant heat loss from the surface to the ground. This article combines two methods organically and uses wind and solar complementary power to drive an electric heater, thereby heating steam. By introducing the volatility index complementarity rate, the supplementary energy effect of electric heating wells in the all-weather wind solar complementary process can be optimized. Then it is substituted into the in-situ transformation model of oil shale. The results show that during the process of simultaneous electric heating and steam injection, the complementary fluctuation of wind-solar energy supply will generate additional secondary seepage channels. This is mainly due to the instantaneous temperature change, which leads to local thermal stress concentration effect. From the perspective of temperature field, fluctuating temperature changes lead to periodic rapid heating in local areas and also trigger the “thermal stress fatigue” effect. At this point, the permeability mainly increases significantly along the path of the main damage fracture evolution. This provides a new technological approach for efficient in-situ upgrading and development of oil shale.

Keywords Oil shale, heating-steam synergistic, wind-solar energy supply, complementary fluctuation, fracture evolution