Low-Cost, High-Performance Chemicals for Enhanced Oil Recovery

Abstract

The ability to select low-cost, high-performance surfactants for a wide range of crude oils under a wide range of reservoir conditions has improved dramatically in recent years. We have developed surfactant formulations (surfactant, co-surfactant, co-solvent, alkali, polymer, electrolyte) using a refined phase behavior approach. Such formulations nearly always result in more than 90% oil recovery in both outcrop and reservoir cores when good surfactants with good mobility control are used. Chemical flood residual oil saturations are typically less than 0.04 and surfactant retention between 0.01 and 0.1 mg/g with these formulations using as little as 0.2% surfactant concentration and 30% pore volume ASP slugs. We describe some of the advances that have improved the performance, reduced the cost, increased the robustness, and extended the range of reservoir conditions for these formulations. There are thousands of possible combinations of the chemicals that could be tested for each oil and each chemical combination requires many observations over a long time period at reservoir temperature for proper evaluation, so it would take too long, cost too much and in many cases not even be feasible to test all combinations. In practice we use our scientific understanding of how to match up the surfactant/co-surfactant/co-solvent characteristics with the oil characteristics, temperature, salinity, hardness and so forth. We have synthesized and tested new surfactants with much larger hydrophobes and more branching than previously available. We have tested new classes of co-solvents and cosurfactants with superior performance. These new developments have enabled us to develop good formulations for both oils that react with alkali to make soap and oils that do not. We have significantly lowered the chemical cost needed for waxy crudes with very high equivalent alkane carbon numbers. We have good results for oils with API gravities as low as 17, high temperature, high salinity, and high hardness brines. Many of these developments are synergistic and taken together represent a breakthrough in reducing the cost of chemical flooding and thus its commercial potential in both sandstone and carbonate reservoirs. SPE 129978ordered arrays such as gels or liquid crystals and decreases the reliance on alcohols or other co-solvents for rapid equilibration of microemulsions. Branched co-surfactants with different structures than the primary surfactant can be added to disrupt the orderly arrangement of surfactant molecules at interfaces (

Design of an optimal middle phase microemulsion for ultra high saline brine using hydrophilic lipophilic deviation (HLD) method

“…Most of the suggested formulations for high salinity brines are developed either for brines up to 21 wt % NaCl without hardness [19] or brines containing hardness up to 8,500 mg/l with a total TDS of 165,000 mg/l [23]. In this work, surfactant formulations for reservoir brine having total TDS of over 300,000 mg/l with the total hardness of about 13,000 mg/l are reported.…”

“…Therefore, surfactants having sulfonate or carboxylate head groups are suggested for reservoirs with higher temperature conditions [18]. Another class of surfactant, that is sodium alkyl ethoxy sulfate [19], is also reported to show promising results in high salinity brines. This class of surfactant is usually used as a co-surfactant in a surfactant mixture to enhance the overall hardness tolerance of surfactant mixture.…”

Novel Large-Hydrophobe Alkoxy Carboxylate Surfactants for Enhanced Oil Recovery

“…Yang et al (2010) recently reported numerous alkali/surfactant/ polymer (ASP) coreflooding results for viscous oils. Viscous oils with low gravity (in 8API) are usually active (contain organic acids that react with alkali to form soap).…”

“…All the corefloods were performed vertically in a convection oven at reservoir temperature. One can find more details of the coreflood procedure in Zhao et al (2008), Levitt et al (2009), Flaaten et al (2010, and Solairaj et al (2012). One can find the procedure for measuring the surfactant concentration with high-performance liquid chromatography (HPLC) (including the procedure for preparing the effluent samples before the HPLC measurements) in Solairaj (2011).…”

“…A better understanding of the relationship between the surfactant structure and performance has improved the process of screening and identifying suitable high-performance surfactants for EOR (Solairaj 2011;Solairaj et al 2012). The use of microemulsion phasebehavior observations used in this study is a very efficient way to screen surfactants (Jackson 2006;Zhao et al 2008;Levitt et al 2009;Flaaten et al 2010;Solairaj et al 2012). Adkins et al (2010) demonstrated that Guerbet alkoxy sulfates made with large hydrophobes exhibited good performance under a wide range of conditions.…”