Preliminary Study of In-situ Combustion in Heavy Oil Field in the North of Thailand

A small oil field in the north of Thailand has medium viscous and low gas-content heavy oil. Since conventional production methods are ineffective, thermal recovery is potentially suitable to enhance oil recovery for this reservoir. In -situ combustion is a complex EOR process used for medium to heavy crude oils. The process involves the multi-phase fluid flow through porous media with chemical and physical transition of the crude oil components under high temperature and pressure conditions. The simulation results with STARS were investigated by conducting a number of sensitivity studies with varying the parameters like gridblock sizes, air-injection rates, oxygen concentrations, and injected air temperature. The 0.5m-block size was chosen due to the optimum running time with acceptable accuracy. From the results, it can be concluded that changing injection rate from 100 Mscf/d to 400 Mscf/d does not significantly affect cumulative oil production – less than 6% incremental recovery. Increase oxygen concentration from 29% to 100% shows an increase in 40.67% oil production. Moreover, if the injected fluid temperature is increased from 80˚F to 500˚F, total oil production increases 97.14%. Furthermore, optimal operating conditions to enhance recovery of oil were also studied.