Surfactants in enhanced oil recovery

Mobility control, issues in, 18 626 Mobility control agents polyacrylamides as, 18 625 in polymer flooding, 18 622 Mobility control surfactants, in enhanced oil recovery, 18 625-628 Mobilizable vectors, for genetic manipulation, 12 471 Mobilization, of ascorbic acid, 25 771 Modacryhc fibers, 9 192 11 188, 189, 190 dyesite content of, 11 195 flame resistance of, 11 214 flammability of, 11 194 pigmented, 11 213 U.S. production of, 11 220t Mode conversion phenomenon, 17 422 Model agreements, 24 373-374 Model-based methods, for reliability, 26 1044... 

Multicomponent phase ecjuilibria involving three or more coexisting fluid phases is frequently encountered in liquefied natural gas processes (1), tertiary oil recovery by miscible gas displacement (2), and the use of surfactants in enhanced oil recovery (3). 

Petroleum sulfonates are widely used as solubilizers, dispersants (qv), emulsifiers, and corrosion inhibitors (see Corrosion and corrosion inhibitors). More recentiy, they have emerged as the principal surfactant associated with expanding operations in enhanced oil recovery (66). Alkaline-earth salts of petroleum sulfonates are used in large volumes as additives in lubricating fluids for sludge dispersion, detergency, corrosion inhibition, and micellar solubilization of water. The chemistry and properties of petroleum sulfonates have been described (67,68). Principal U.S. manufacturers include Exxon and Shell, which produce natural petroleum sulfonates, and Pilot, which produces synthetics. 

The use of AOS and other surfactants as steam-foaming agents has been studied by several oil companies in laboratories and in the field [55-62]. In the next section we will view olefinsulfonate structure-property relations [40] that have helped design optimum surfactants for enhanced oil recovery applications. 

Wetting is an absolute condition for detergency. However, wetting plays an important role in other applications as well. A special case is the penetration of fluids in porous material. That may be a bundle of fibers in the dying process or the stone matrix in enhanced oil recovery. One of the steps of lubrication is wetting of surfaces by lubricant liquids. Because other conditions must also be considered, the use of phosphorus-containing surfactants is beneficial. 

Solubilizing activity are also used in enhanced oil recovery. Tar and extremely viscous hydrocarbons are recovered by the injection of an aqueous solution of an anionic orthophosphate ester surfactant into a petroleum formation, retaining the surfactant in the formation for about 24 h, and displacing the solubilized hydrocarbons toward a recovery well. The surfactant forms an oil microemulsion with the hydrocarbons in the formation. An anionic monoorthophosphate ester surfactant which is a free acid of an organic phosphate ester was dissolved in water. The input of surfactant solution was 2-25% of the pore volume of the formation [250]. To produce a concentrate for the manufacture... 

B. Bubela. In situ biological production of surfactants for enhanced oil recovery. Australia Dep Resources Energy End of Grant Rep 151, March 1983. 

Petroleum recovery typically deals with conjugate fluid phases, that is, with two or more fluids that are in thermodynamic equilibrium. Conjugate phases are also encountered when amphiphiles fe.g.. surfactants or alcohols) are used in enhanced oil recovery, whether the amphiphiles are added to lower interfacial tensions, or to create dispersions to improve mobility control in miscible flooding 11.21. 

Surfactant-polymer flooding, 13 628 Surfactant precipitation, in volumetric sweep efficiency, 13 621 Surfactant propagation, in enhanced oil recovery, 13 629... 

Recent years have seen a revival of interest in the study of surfactants and their properties, in part due to their potentialities for use in enhanced oil recovery. In addition, greater awareness of the effects of impurities, the availability of a variety of high-purity surfactants from a number of commercial sources, and improved methods for characterizing and purifying materials have resulted in an increased number of investigations containing data on surfactant properties from which reliable conclusions can be drawn. 

The important role of the structure of the surfactants in determining adsorption is evident. Some of the surfactants discussed above can produce low interfacial tension and some others have excellent salt tolerance. A knowledge of the structure of such surfactants in adsorption can be helpful in developing surfactants that will meet different requirements simultaneously for special applications such as in enhanced oil recovery. 

The point at which, supposedly, 50% of the acid species is transformed in salt corresponds to the half-neutrahzation, i.e., when half the alkahne required to reach the equivalence point has been added. This position corresponds to a buffer zone in which the variation of pH is small with respect to the amoimt of added neutralization solution (Fig. 14 left plot). Hence, in this region a very slight variation of pH can produce a very large variation of neutralization (Fig. 14 right plot), i.e., a considerable alteration of the relative proportion of AH and A . Far away from this pH, the opposite occurs. Consequently, the pH could be used to carry out a formulation scan, but the scale is far from hnear and the variation of pH does not render the variation of the characteristic parameter of the actual surfactant mixture that is at interface [77,78]. The appropriate understanding of the behavior of this kind of acid-salt mixture is particularly important in enhanced oil recovery by alkaline flooding [79,80] and emulsification processes that make use of the acids contained in the crude oils [81-83]. 

This brief review has attempted to discuss some of the important phenomena in which surfactant mixtures can be involved. Mechanistic aspects of surfactant interactions and some mathematical models to describe the processes have been outlined. The application of these principles to practical problems has been considered. For example, enhancement of solubilization or surface tension depression using mixtures has been discussed. However, in many cases, the various processes in which surfactants interact generally cannot be considered by themselves, because they occur simultaneously. The surfactant technologist can use this to advantage to accomplish certain objectives. For example, the enhancement of mixed micelle formation can lead to a reduced tendency for surfactant precipitation, reduced adsorption, and a reduced tendency for coacervate formation. The solution to a particular practical problem involving surfactants is rarely obvious because often the surfactants are involved in multiple steps in a process and optimization of a number of simultaneous properties may be involved. An example of this is detergency, where adsorption, solubilization, foaming, emulsion formation, and other phenomena are all important. In enhanced oil recovery. 

Lignosulfonates - pULP] (Vol 20) - [SULFONATION AND SULFATION] (Vol 23) - [SURFACTANTS] (Vol 23) -drilling mud thinner PETROLEUM - DRILLING FLUIDS] (Vol 18) -in enhanced oil recovery PETROLEUM - ENHANCED OIL RECOVERY] (Vol 18)... 

Micro-foam, or colloidal gas aphrons have also been reportedly used for soil flushing in contaminated-site remediation [494—498], These also have been adapted from processes developed for enhanced oil recovery (see Section 11.2.2.2). A recent review of surfactant-enhanced soil remediation [530] lists various classes of biosurfactants, some of which have been used in enhanced oil recovery, and discusses their performance on removing different type of hydrocarbons, as well as the removal of metal contaminants such as copper and zinc. In the latter area, the application of heavy metal ion complexing surfactants to remediation of landfill and mine leachate, is showing promise [541]. 

Austad, T. Milter, J. Surfactant Flooding in Enhanced Oil Recovery in Surfactants, Fundamentals and Applications in the Petroleum Industry, Schramm, L.L. (Ed.), Cambridge University Press Cambridge, 2000, pp. 203-249. 

The stability of emulsion and foam films have also been found dependent upon the micellar microstructure within the film. Electrolyte concentration, and surfactant type and concentration have been shown to directly influence this microstructure stabilizing mechanism. The effect of oil solubilization has also been discussed. The preceding stabilizing/destabilizing mechanisms for three phase foam systems have been shown to predict the effectiveness of aqueous foam systems for displacing oil in enhanced oil recovery experiments in Berea Sandstone cores. 

Foam exhibits higher apparent viscosity and lower mobility within permeable media than do its separate constituents.(1-3) This lower mobility can be attained by the presence of less than 0.1% surfactant in the aqueous fluid being injected.(4) The foaming properties of surfactants and other properties relevant to surfactant performance in enhanced oil recovery (EOR) processes are dependent upon surfactant chemical structure. Alcohol ethoxylates and alcohol ethoxylate derivatives were chosen to study techniques of relating surfactant performance parameters to chemical structure. These classes of surfactants have been evaluated as mobility control agents in laboratory studies (see references 5 and 6 and references therein). One member of this class of surfactants has been used in three field trials.(7-9) These particular surfactants have well defined structures and chemical structure variables can be assigned numerical values. Commercial products can be manufactured in relatively high purity. 

Achievement of low mobility ratios at the fronts between displacing and displaced fluids is of even greater concern in enhanced oil recovery than in waterflooding owing to the high costs and/or low viscosities of the injected fluids. One response to this concern has been the continuing effort to develop a fundamental understanding of so-called foam flow, which employs aqueous solutions of properly chosen surfactants at relatively low capillary numbers to reduce the effective mobility of low viscosity fluids (see 5,6 and papers on foam flow in this volume). 

A critical literature review on foam rheology is given elsewhere (6). The injection of foam-like dispersions or C02 foams is a useful method in enhanced oil recovery ( 7). This method of decreasing the mobility of a low-viscosity fluid in a porous rock requires the use of a surfactant to stabilize a population of bubble films or lamellae within the porespace of the rock (8). The degree of thickening achieved apparently depends to some extent on the properties of the rock itself. These properties probably include both the distance scale of the pore space and the wettability, and so can be expected to differ from reservoir to reservoir, as well as to some extent within a given field (9,10). 

---