A Study of Branched Alcohol Propoxylate Sulfate Surfactants for Improved Oil Recovery
- Yongfu Wu (California Institute of Technology) | Patrick J. Shuler (California Institute of Technology) | Mario Blanco (California Institute of Technology) | Yongchun Tang (California Institute of Technology) | William A. Goddard (California Institute of Technology)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 9-12 October, Dallas, Texas
- Publication Date
- Document Type
- Conference Paper
- 2005. Society of Petroleum Engineers
- 1.6.9 Coring, Fishing, 4.1.5 Processing Equipment, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 2.5.2 Fracturing Materials (Fluids, Proppant), 6.5.2 Water use, produced water discharge and disposal, 5.4.1 Waterflooding, 5.3.2 Multiphase Flow, 5.2.1 Phase Behavior and PVT Measurements, 4.1.2 Separation and Treating
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This investigation considers one class of anionic surfactant, a series of branched alcohol propoxylate sulfate surfactants, as candidates for chemical EOR applications.This experimental results show that these surfactants may be preferred candidates for EOR as they can be effective at creating low interfacial tension (IFT) at dilute concentrations, and without requiring an alkaline agent or cosurfactant.In addition, some of the formulations exhibit a low IFT at several percent sodium chloride concentrations, and hence may be suitable for use in more saline reservoirs.
Adsorption tests onto kaolinite clay indicate that the loss of these surfactants can be comparable to or greater than other types of anionic surfactants.
Surfactant performance was evaluated in oil recovery core flooding tests.Selected formulations could displace most of the waterflood residual oil in place even with dilute, 0.2 wt% surfactant solutions from Berea sandstone cores.
Surfactant enhanced oil recovery (EOR) has been investigated for many years, especially starting in the 1970's and 1980's when the technology was put on a sound scientific basis.Unfortunately, the economic reality of the process performance as experienced in early field trials largely precluded widespread deployment of this technology.However, the recent surge in crude oil process has provided new impetus to consider employing chemical EOR.
The basic physics behind the surfactant flooding EOR process is that the residual oil dispersed as micron-size ganglia is trapped by high capillary forces within the porous media.Increasing the fluid flow viscous forces or decreasing the capillary forces holding the oil in place are required before the oil can be pushed through the pore throats and sent on to a production well.The rule of thumb for a successful surfactant flood is that the interfacial tension between the crude oil and the aqueous phase needs to be reduced to ultra-low values, (target 0.001 mN/m), several orders of magnitude below that of a typical reservoir brine-oil system.
Besides the requirement to achieve a low in-situ IFT, another major factor that determines the technical and economic success of a surfactant flood project is to minimize the depletion of the injected surfactant, with the major sink usually from solid adsorption onto clays in the reservoir.
A wide variety of surfactant has been investigated for their potential efficacy for chemical EOR applications.With this renewed interest in surfactant EOR, there is now the opportunity to investigate surfactants not available or not previously investigated during this earlier development of chemical EOR technology.In part, for this reason, branched alcohol propoylated sulfates were selected for this study.
Branched alcohol propoylated sulfates have emerged as an effective type of surfactant for the removal of nonaqueous phase liquids (NAPLs) from near surface, aquifer contaminated sites[1,2].This application to remediate shallow subsurface aquifers by injecting a surfactant solution is a relatively recent technology.This investigation considers these same surfactants as EOR agents for oilfield applications.
Propoxylated sulfate surfactants have been shown to create middle-phase micoemulsions versus crude oils, and presumably achieve low interfacial tensions.Another study demonstrated surfactants as mixtures of ethoxylated and propoxylated products could be formulated to provide optimum performance for different oils and process conditions.Another motivation for this research is the need for high performance surfactants and that surfactants with branched-chain alkyl groups are shown in a recent study to have lower IFT than those with straight-chain alkyl groups.The specific surfactants selected for this study are 18 different branched alcohol propoxy sulfates, of the Alfoterra® mn (m=1, 2, 3, 4, 5, 6; n=3, 5, 8) series supplied by Sasol Corporation.
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