Data for the high-water-content process portion of the El Dorado Micellar-Polymer Demonstration Project were assessed relevant to evaluation of the project by numerical simulation. The data adequacy was measured against the data requirements for INTERCOMP's Chemical Flooding Ternary Equilibrium simulator.

Two principal types of polymers are currently used for polymer flooding: synthetic polymers called partially hydrolyzed polyacrylamides (HPAM) and a biologically-produced polysaccharide known as xanthan gum (XG). The generalized structures of these two polymers are shown in Figures 1 and 2, respectively. Although both types of materials have been successfully used in field applications, each suffers limitations that result in process inefficiencies or loss of cost effectiveness. Problems common to both polymer types include difficulties encountered with injection of polymers, especially where the reservoir permeability is low; interactions between surfactants and polymers; degradation caused by the presence of oxygen; and availability of bactericides which are compatible with the polymers. Problems specific to the use of XG include bacterial degradation, injection well impairment, and filtration requirements. Problems encountered primarily with HPAM include viscosity loss in brine, especially brines containing calcium and magnesium ions, and the necessity for special handling to prevent degradation by shearing. Although field tests are being conducted with both types of polymers, the majority of the field projects are using HPAM, probably because of economic considerations.

Modeling and Optimizing Surfactant Structure to Improve Oil Recovery by Chemical Flooding at the University of Texas DOE/BC/10841-10

DOE/BC/10841-5

The effects of temperature and of divalent ion concentration on the structure of aqueous surfactant solutions have been determined. As temperature increases, the salinity range where liquid crystalline phases exist is narrowed. At sufficiently high temperatures the liquid crystal "melts" and only isotropic phases are observed. These are an aqueous phase and, when partial immiscibility of alcohol and brine occurs, an alcohol rich phase as well. The effect of divalent ions on aqueous solution structure is basically the same as that of monovalent ions, but smaller quantities of divalent ions are needed to bring about the same phase changes. In the particular system studied addition of one mole of Ca+ was equivalent to addition of about 11.5 moles of Na+. We have extended our model of drop size in microemulsions to include the effect of drop dispersion. A hard sphere model was used to describe dispersion effects. With dispersion, drop size is slightly smaller for both oil-continuous and water-continuous microemulsions than predicted by the previous analysis which considered film properties alone.

DOE/BC/10841-15 Modeling and Optimizing Surfactant Structure to Improve Oil Recovery by Chemical Flooding at the University of Texas--Final Report

Research on Surfactant-Polymer Oil Recovery Systems, Progress status report, April 1-June 30, 1979

Research on Surfactant-Polymer Oil Recovery Systems, Project status report, January 1-March 31, 1979

DOE/BC/10845-15

Surfactant-Enhanced Bicarbonate Flooding, Final Report, October 1986

Surfactant-enhanced alkaline flooding with weak alkalis The objective of Project BE4B in FY90 was to develop cost-effective and efficient chemical flooding formulations using surfactant-enhanced, lower pH (weak) alkaline chemical systems. Chemical systems were studied that mitigate the deleterious effects of divalent ions. The experiments were conducted with carbonate mixtures and carbonate/phosphate mixtures of pH 10.5, where most of the phosphate ions exist as the monohydrogen phosphate species. Orthophosphate did not further reduce the deleterious effect of divalent ions on interfacial tension behavior in carbonate solutions, where the deleterious effect of the divalent ions is already very low. When added to a carbonate mixture, orthophosphate did substantially reduce the adsorption of an atomic surfactant, which was an expected result; however, there was no correlation between the amount of reduction and the divalent ion levels. For acidic oils, a variety of surfactants are available commercially that have potential for use between pH 8.3 and pH 9.5. Several of these surfactants were tested with oil from Wilmington (CA) field and found to be suitable for use in that field. Two low-acid crude oils, with acid numbers of 0.01 and 0.27 mg KOH/g of oil, were studied. It was shown that surfactant-enhanced alkaline flooding does have merit for use with more »these low-acid crude oils. However, each low-acid oil tested was found to behave differently, and it was concluded that the applicability of the method must be experimentally determined for any given low-acid crude oil. 19 refs., 10 figs. 4 tabs.

Surfactant flooding is flexible because of the ability to optimize formulations for a wide range of reservoir conditions and crude oil types. The objective for this work was to determine if the addition of alkaline additives will allow the design of surfactant formulations that are effective for the recovery of crude oil, while, at the same time, maintaining the surfactant concentration at a much lower level than has previously been used for micellar flooding. Specifically, the focus of the work was on light, midcontinent crudes that typically have very low acid contents. These oils are typical of much of the midcontinent resource. The positive effect of alkaline additives on the phase behavior of the surfactant formulations and acidic crude oils is well known. The extension to nonacidic and slightly acidic oils is not obvious. Three crude oils, a variety of commercial surfactants, and several alkaline additives were tested. The oils had acid numbers that ranged from 0.13, which is quite low, to less than 0.01 mg KOH/g of oil. Alkaline additives were found to be very effective in recovering Delaware-Childers (OK) oil at elevated temperatures, but much less effective at reservoir temperatures. Alkaline additives were very effective with Teapot Dome (WY) oil. With Teapot Dome oil, surfactant/alkali systems produced ultralow IFT values and recovered 60% of the residual oil that remained after waterflooding. The effect of alkaline additives on recovering Hepler (KS) oil was minimal. The results of this work indicate that alkaline additives do have merit for use in surfactant flooding of low acid crude oils; however, no universal statement about applicability can be made. Each oil behaves differently, with this treatment, and the effect of alkaline additives must be determined (at reservoir conditions) for each oil. 23 refs., 13 figs., 3 tabs

This report covers research performed through September 1982 on the project, "Vapor Pressure Studies of the Solubilization of Hydrocarbons by Surfactant Micelles". Quarterly reports were also submitted for the periods Sept. 1 - Dec. 31, 1981; Jan. 1 - Mar. 31, 1982; and Apr. 1 to Jun 30, 1982. With the concurrence of the sponsor, research results for the period July to September 1982 will be included here; a separate quarterly report will not be issued.