Influences of geological heterogeneity on heat extraction from deep high water cut oil reservoirs by flue gas recycling: Insights from numerical simulations

Abstract

Heat extraction from high temperature oil reservoirs featured with high water cut is a promising way for geothermal exploitation. Heat mining via flue gas recycling is considered as an alternative way for water or CO2 circulation. However, how permeability heterogeneity and flue gas composition impact the heat extraction efficiency are not clearly understood. In this work, heat extraction from high water cut oil reservoirs via flue gas recycling based on existing inverted five-spot well pattern is systematically investigated through geostatistical modelling and numerical simulations. The influences of horizontal autocorrelation length, global permeability heterogeneity (in terms of Dykstra-Parsons coefficient), averaged permeability, and flue gas composition on the heat extraction performance are comprehensively explored. The simulation results indicate that the increase of horizontal autocorrelation length can improve the heat mining rate to a certain degree. The enhancement of global permeability heterogeneity can obviously deteriorate the heat mining performance. High water cut oil reservoirs with a moderate mean permeability (e.g., 100 mD) may be more feasible for heat extraction via flue gas recycling. Flue gas with higher CO2 contents is more suitable for being as working fluids for heat extraction. The findings of this research can provide meaningful guidance for the selection of feasible high temperature post waterflooded oil reservoirs for heat production via flue gas circulation.