Feasibility Study of In Situ Combustion Huff and Puff for EOR in Super Deep Heavy Oil Reservoir

LKQ oil field is a super-deep heavy oil reservoir with the dead oil viscosity of 9,680~12,000mPa.s at 50, the depth at 2,100 m~3,200 m and the reservoir temperature at 60~95°C. High oil viscosity and low flowability result in low production and rapid decline of primary development. The steam injection, as its low thermal efficiency, is not suitable for the super-deep heavy oil reservoir. In situ combustion is a promising oil recovery process in which thermal energy is generated inside the reservoir. However, the LKQ oil field has a reservoir depth of more than 2000m, no heavy oil field with such a high reservoir depth has applied high pressure in situ combustion all over the world. For the reasons, it is decided to study the feasibility of producing the field by in-situ combustion huff and puff (ISCHF) to enhance oil recovery. In this paper, the mechanism of ISCHF was analyzed firstly, and then a 3-D numerical model was constructed using STARS reservoir simulator to study the operating parameter and the economical efficiency of the ISCHF. As oxygen and natural gas may be produced together which may result in explosion, the security measures were researched by using numerical simulation. According to the simulation results, the fire line can advance symmetrically toward radial direction after the ignition; the oil was displaced to production well by steam, water and flue gas in the back production process; the accumulative air-oil ratios is below 1,000; and the oxygen content in the production gas is blow 3% if a nitrogen slug was injected after air injection stopped. The results can be used to ISCHF design and has great instruction meaning for the super-deep heavy oil reservoir development.