Summary
We report results for a number of promising enhanced-oil-recovery (EOR)
surfactants based upon a fast, low-cost laboratory screening process that is
highly effective in selecting the best surfactants to use with different crude
oils. Initial selection of surfactants is based upon desirable surfactant
structure. Phase-behavior screening helps to quickly identify favorable
surfactant formulations. Salinity scans are conducted to observe equilibration
times, microemulsion viscosity, oil and water-solubilization ratios, and
interfacial tension (IFT). Cosurfactants and cosolvents are included to
minimize gels, liquid crystals, and macroemulsions and to promote rapid
equilibration to low-viscosity microemulsions. Branched alcohol propoxy
sulfates (APS), internal olefin sulfonates, and branched alpha olefin
sulfonates (AOS) have been identified as good EOR surfactants using this
screening process. These surfactants are available at a low cost and are
compatible with both polymers and alkali, such as sodium carbonate and, thus,
are good candidates for both surfactant-polymer and alkali-surfactant-polymer
EOR processes. One of the best formulations was tested in both sandstone and
dolomite cores and found to give excellent oil recovery and low surfactant
retention with a west Texas (WT) crude oil.
Introduction
Recent advances, including the development of new synthetic surfactants and
increased understanding of the structure/performance relationship of
surfactants, have made it possible to rapidly identify promising
high-performance surfactants for EOR. This process involves laboratory
screening using knowledge of the molecular structure and cost of the
surfactants as well as pertinent reservoir-specific information (i.e.,
temperature, salinity, and crude-oil properties).
This paper describes a process for identifying and evaluating potential EOR
surfactants. The surfactant selection process starts with the screening of
surfactants by phase-behavior experiments and progresses to corefloods with
formulations that may incorporate cosurfactants, cosolvents, alkali, polymers,
and electrolytes. We illustrate the application of this approach to the
selection of a surfactant formulation for use in both a sandstone outcrop and a
WT dolomite reservoir, but focus mostly on the dolomite application because
very few studies have been reported for carbonate (Adams and Schievelbein 1987)
or dolomite reservoirs. These laboratory data were used in a parallel
simulation study of the same reservoir and are described by Anderson et al.
(1976) in a companion paper.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
17 February 2006
- Meeting paper published:
22 April 2006
- Revised manuscript received:
25 July 2008
- Manuscript approved:
11 August 2008
- Published online:
15 April 2009
- Version of record:
15 April 2009
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