Evaluation of Emulsified Solvent Flooding For Heavy Oil Recovery (1995)

Abstract Efficient secondary and tertiary recovery a/heavy oil from thin reservoirs Isuch as chose in the Lloydminster area, remains an unsolved challenge to IORresearchers. The primary recovery from these heavy oil reservoirs is generallypoor (often &amp;lt; 5% OOIP) and waterflooding is rather inefficient due tovery adverse mobility ratio which results in severe viscous fingering and earlywater breakthrough. Thermal method are also not viable due to excessive heatlosses to the underlying and overlying formations. Non- thermal techniquesinvolving injection of a miscible solvent are uneconomical due to the high caseof solvent in relation to the market value of the heavy oil recovered.Therefore, there is a need for novel processes designed specifically for suchreservoirs. This paper presents an experimental evaluation of the use of emulsifiedsolvents to recover heavy oil from thin reservoirs. The emulsified solventflooding can potentially provide the high recovery efficiency of misciblesolvents at a fraction of the cost. The process, if successful, would havewideapplication in thin heavy oil reservoirs. Commercially available emulsifiers were used to formulate solvent-in-wateremulsions using natural gas condensate or petroleum naphtha as the solvent. Theoil recovery potential of these emulsions was evaluated in one meter longlinear sand-packs and in a three-dimensional glass-bead packed isual model.Effects of various process variable, including: solvent volume fraction, surfactant concentration; flow velocity, and oil viscosity, on oil recoveryperformance were experimentally evaluated. The results show that the emulsified solvent flooding provides significantlysuperior displacement efficiency compared to straight solvent injection andwaterflooding. The mechanisms responsible for such high efficiency include:reduction in oil viscosity due to dilution by the solvent;mobility controlprovided by the trapping of emulsion droplets at pore throats; andin-situemulsification of the oil being displaced. The relative importance of thesemechanisms was evaluated under different conditions. An economic analysis showed that, although the process can recover a largefraction of the oil in place, it would not be profitable under current priceconditions. Several novel ideas for improving the performance aresuggested. Introduction Vast reserves of heavy oil which can be mobilized at reservoir conditions existin the Lloydminster area of east central Alberta and west central Saskatchewan.Although the oil in these reservoirs is mobile, its production is hampered byhigh viscosity and the primary recovery is typically between five to tenpercent. Enhanced recovery by steam injection is generally not profitable inthese, relatively thin, reservoirs because of excessive heat losses to thesurrounding rock formations. Non-thermal techniques involving injection of amiscible solvent are also uneconomical due to the high cost of solvent inrelation to the market value of the heavy oil recovered. Therefore, newrecovery processes are needed to economically recover the heavy oil from thesereservoirs. One attractive alternative to miscible solvent injection appears to be the Emulsified Solvent Flooding process. It has the potential to provide the highdisplacement efficiency of a miscible f1ood at a significantly lower cost dueto the reduced solvent requirements.