This research was designed to develop an efficient micellar/polymer flooding process for the tertiary recovery of selected light oils in Alberta. Two systems, specifically for Bonnie Glen crude and Provost crude, were developed to mobilize the waterflood residual oil. The effect of various types of preflushes on tertiary recovery and the process efficiency* was investigated. Effect of the multiplicity of micellar slugs as well as the graded micellar slugs on tertiary recovery were also studied.
Over 100 core displacement tests were carried out in 5 cm diameter × 61 cm long Berea sandstone cores using a series of carefully formulated micellar slugs, with and without a preflush. A frontal velocity of ~1.3 m/day was employed.
Tertiary recovery was sensitive to the type and slug size of the preflushes used. Significant increase in tertiary recovery was achieved by utilizing a suitable preflush such as sodium carbonate or EDTA. Suitably "tailored" composite micellar slugs were found to be far more effective than single slugs to enhance tertiary oil recovery. A graded composite slug proved to be superior to all other slug/polymer combinations employed, in improving the efficiency as well as the economics in both the systems developed.
Micellar flooding is one of the very few processes, which have been shown to be successful in recovering oil from a watered-out light oil reservoir. Many large field tests conducted in the U.S. support the effectiveness of the micellar flooding process. The economics of the process remain dubious in view of the cost of the chemicals used and the small spacing usually employed in field tests.
The purpose of this investigation was to develop micellar solutions for two Alberta crude oils (Bonnie Glen and Provost crudes). The emphasis was on improving process efficiency (i.e. volume of oil recovery per unit mass of sulphonate) by means of a number of strategies, including the use of preflushes and graded micellar solutions.
Much work has been reported on the micellar flooding process by various investigators. The earliest papers by Gogarty and Tosch3, Davis and Jones9 provide insight into the process mechanism. Recent work by Healy and Reed4,5, Pope6, Sayyouh and Farouq Ali7, Enedy and Farouq Ali8, Novasad et al.10 have been instrumental in finding ways of improving process efficiency. A current review of these and other papers on the subject is provided by Daharu2.
Process efficiency of the micellar/polymer process can be defined as the tertiary oil recovery per unit volume of slug injected.
The micellar/polymer flooding process as an enhanced oil recovery method for a watered-out reservoir is increasingly being employed by the industry. Hydrocarbon, water/brine and surfactant are the basic components of a micellar solution. A small amount of alcohol is often used to improve solution stability, to adjust the viscosity, and to reduce surfactant loss due to adsorption on the reservoir rock. A suitably formulated micellar slug miscibly displaces the residual oil and improves tertiary recovery.
