EXPERIMENTAL AND SIMULATION STUDIES ON STEAM STIMULATION WITH MULTIPLE FLUIDS FOR OFFSHORE HEAVY OIL RESERVOIRS

Abstract. Steam flooding and stimulation processes have proven to be the most promising method for the commercial in situ recovery of heavy oil. For high quality and thick oil reservoirs, these processes can achieve an oil recovery factor of over 30 % OOIP. However, for thin, deep and offshore oil reservoirs, they are uneconomic due to the excessive heat loss to the overburden and great heat requirement to heat the reservoir rock. A new process, Steam and Multiple Fluids (SMF), is being developed to improve the efficiency of the steam stimulation process for offshore heavy oil reservoirs. It involves a combination of steam and non-condensable gases. The injected gases accumulate in the region away from the well and lower the temperature. Only the regions temperature near the well is close to the temperature of steam. The heat loss to the overburden and the heat requirement to heat the reservoir rock can be significantly reduced due to a lower temperature requirement. Considerable saving can be achieved from the reduction in the quantity of steam required for the process. This process is studied by using laboratory experiments and numerical simulations via a 3D thermal model for an offshore heavy oilfield. The results show that, compared to the cold production and standard steam stimulation processes, the oil recovery factor from the SMF is the highest. The application of this process makes the production of offshore heavy oil economic and should extend the range of reservoirs that can be produced economically. A pilot test for calibrating this new process is also reported