Heavy oil has attracted global attention due to its huge volume of original oil in place. However, there are numerous operation and economic challenges to the recovery of heavy oil due to its high-viscosity and high-density. Thermal recovery methods such as steam injection is viable and commonly used to recover heavy oil and bitumen primarily by viscosity reduction of heavy oil and improving the displacement of the heavy oil. However, there are significant heat losses before the steam reaches the heavy-oil reservoir, in addition to the concerns of high cost and emission of greenhouse gases. One of the promising new heavy-oil recovery approaches is generating steam with nitrogen gas, in-situ, using thermochemical reaction to reduce oil viscosity, improve the mobility ratio and enhance the heavy-oil displacement. Steam and nitrogen are generated, in-situ, by injecting exothermic reactants downhole with the injected water to create heat and enhance reservoir pressure for mobilizing heavy oil. The exothermic reaction is triggered by either increasing downhole temperature or in the presence of a low pH weak acid.

In this research, a numerical study of the novel heavy oil recovery process using in-situ steam and nitrogen generated by thermochemical reactions in field scale is conducted. Various ratios of nitrogen- steam are studied to identify their effect on the recovery efficiency. In-situ Nitrogen-steam ratio generated by thermochemical is optimized to accomplish the maximum achievable net present value (NPV) after ten years of recovery. The CMG STARS simulator is used to simulate reservoir models with different operational parameters.

The results show that the generated heat from in-situ thermochemical reactions was sufficient to reduce the viscosity of heavy oil, while the generated nitrogen gas provided a good heat insulation effect and reduced steam-oil ratio. Thus, higher NPV was achieved than typical conventional steam-only injection method.

This is the first time NPV and all economic parameters are considered to analyze the performance of an in-situ steam and nitrogen generated by thermochemical reaction. This research shows that the recovery of the proposed method is more suitable and economical for the reservoirs which are not viable for conventional steam flooding methods and it is a step forward to eliminate CO2 emissions associated with thermal recovery process.

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