Steam flooding and stimulation processes have proven to be the most promising method for commercial in situ recovery of heavy oil. For high quality and thick oil reservoirs, these processes can achieve oil recovery of over 30% OOIP. However, for thin, deep and offshore oil reservoirs, they are uneconomic due to excessive heat loss to overburden and great requirement to heat the reservoir rock.
A new process, Steam and Multiple Fluids (SMF), is being developed to improve efficiency of the steam stimulation process for offshore heavy oil reservoirs. It involves the addition of non-condensable gases to the injected steam. Injected gases accumulate in the region away from the well and lower the temperature. Only the region’s temperature near the well is close to the temperature of steam. Heat loss to the overburden and the heat requirement to heat reservoir rock can be significantly reduced due to the lower temperature requirement. Considerable saving can be achieved from reduction in 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 rate from SMF is the highest. The application of this process makes 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 reported.