Heavy-Oil Recovery by In-Situ Emulsion Formation

Abstract

The aim of this work is to evaluate alkaline/surfactant (AS) methods to improve recovery from heavy-oil reservoirs. Alkali/surfactant/oil phase-behavior experiments were conducted to determine conditions under which oil-in-water (O/W) emulsions form. The viscosity (and its shear dependence) was measured for some of these emulsions. Reservoir sand was assembled in sandpacks. Waterflood and AS floods were conducted at several salinities. Several relatively hydrophilic surfactants were identified, which formed O/W emulsions with the reservoir oil at a low concentration in the presence of sodium carbonate. O/W emulsions were favored at low salinity and high water/oil ratio (WOR). Viscosity of these emulsions was low compared with the oil viscosity. Waterflood recovery was on the order of 25 to 40% of the original oil in place (OOIP) in corefloods, and it decreased as the injection rate increased. Following the waterflood, the AS flood gave an incremental oil recovery of 10 to 35% of OOIP. The incremental post-breakthrough oil recovery during the waterflood is likely because of the imbibition of the water from viscous fingers into the unswept oil-saturated zone; this recovery is directly proportional to the square root of time.

Wettability Alteration in Carbonate Rocks by Implementing New Derived Natural Surfactant: Enhanced Oil Recovery Applications

“…The anionic surfactants have a different mechanism for wettability alteration. Two mechanisms have been proposed for wettability alteration of these surfactants by Standnes and Austad (2000a, b) and Kumar et al (2012). The two mechanisms are formation of bi-layer between surfactant and adsorbed polar compound and micellar solubilization.…”

Use of Cosolvents To Improve Alkaline/Polymer Flooding

“…The flood did produce some incremental oil and was considered a technical success; however, the result overall was discouraging because little oil was produced (Leach et al 1962). In the Harrisburg field, Nebraska, engineers attempted to alter the wettability of a carbonate reservoir from oil-wet to water-wet in three wells by use of a 2.0 wt% sodium hydroxide (NaOH) slug in a watered-out zone.…”

“…Such light cosolvents tend to reduce the microemulsion viscosity, which is particularly important with heavy crude oils (Walker et al 2012, Kumar et al 2012. ACP flooding has all the advantages of the ASP flooding: polymer for mobility control, high displacement efficiency in properly designed and executed floods, and fully customizable phase behavior, with acceptable optimal salinity and broad regions of ultralow IFT.…”

Use of Co-Solvents to Improve Alkaline-Polymer Flooding

“…The light co-solvents used in this study are small, non-ionic molecules showing no issues with adsorption and/or chromatographic separation. Such light co-solvents tend to reduce the microemulsion viscosity, which is particularly important with heavy crude oils (Walker et al, 2012, Kumar et al, 2012.…”