Numerical simulation on the in situ upgrading of oil shale reservoir under microwave heating

Microwave heating shows great potential in pyrolyzing oil shale with fast heating rate in many laboratory experiments. There are few studies based on numerical simulations to investigate the technical and economic feasibility of microwave on the in situ upgrading of oil shale reservoir. In this study, the mathematical models including electromagnetic field, heat transfer, chemical engineering, mass transfer and fluid flow were presented to simulate the temperature distribution, kerogen decomposition, and production efficiency of oil and gas under microwave heating. The effects of output power level and thermal conductivity of oil shale on the reservoir temperature distribution were investigated to fully understand the mechanism of microwave exploitation. To avoid the superheat region around the heaters, the intermittent heating and stepwise heating modes were proposed and proved to be practical. Also, stepwise microwave heating mode showed better performance than electrical heating in terms of production efficiency and energy consumption. Under microwave irradiation, both porosity and permeability of oil shale can be highly enhanced. Moreover, the seepage channels of the reservoir can also be improved by hydraulic fracturing. Eventually, the time for opening the production well is optimized in order to reduce the secondary oil cracking. The flowing field added into the existing model highly influences the reservoir temperature distribution, kerogen decomposition, and production yield. The results from this study can provide comprehensive understanding of microwave exploitation for oil shale upgrading and valuable guideline for optimizing engineering parameters.

Automated summary

This study presents mathematical models to simulate the temperature distribution, kerogen decomposition, and production efficiency of oil and gas under microwave heating, with a focus on the effects of output power level and thermal conductivity of oil shale on reservoir temperature distribution. The study suggests that intermittent and stepwise heating modes can effectively prevent superheating and improve production efficiency compared to electrical heating.