Mobility control agents

Recent research and field tests have focused on the use of relatively low concentrations or volumes of chemicals as additives to other oil recovery processes. Of particular interest is the use of surfactants as CO (184) and steam mobility control agents (foam). Also combinations of older EOR processes such as surfactant enhanced alkaline flooding and alkaline-surfactant-polymer flooding have been the subjects of recent interest. Older technologies polymer flooding (185,186) and micellar flooding (187-189) have been the subject of recent reviews. In 1988 84 commercial products polymers, surfactants, and other additives, were listed as being marketed by 19 companies for various enhanced oil recovery applications (190). 

The first mobility control agents were partially hydrolyzed polyacrylamides having molecular weights of 1-5x10 (254-259) and... 

The reason for wide-spread interest in the use of surfactants as gas mobility control agents (369) is their effectiveness at concentrations of 0.1%wt (377) or less (364). This low chemical requirement can significantly improve process economics. 

Surfactants have been used as steam mobility control agents in both laboratory and field tests to prevent this gravity override thereby increasing volumetric sweep efficiency. Surfactants that have been... 

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... 

Dispersion and Phase Behavior. The selection of surfactants for high-pressure gas-flood mobility control effectively began in 1978 when Bernard and Holm received a patent on the use of alkyl polyethoxy sulfates SO4M as mobility control agents for... 

These results imply that since residual crude oil composition changes as it undergoes extraction by injected COj, the optimum COj mobility control agent may change during the course of the COj flood. 

Surfactant foaming properties are related to oil phase composition. The composition of the residual oil will change in the course of a COj EOR project. The optimum COj mobility control agent may thus change during the course of the project. 

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. 

Core floods and high pressure sight cell studies are unsuitable for evaluating large numbers of surfactants as mobility control agents because of the long duration of properly designed... 

In these displacement studies it was necessary to limit the presssure drop in the test core to a value comparable to that encountered in reservoir, about 1 psi/ft. Excessive pressure gradients can artiflcially cause oil to flow as a consequence of providing sufficient force to overcome the lowered interfacial tension produced by the surfactants. The swelling of the oil accompanied by a significant decrease in viscosity makes it possible to follow carbon dioxide with water injection to effectively recover additional oil in the immiscible oil displacement process. Tests were performed in this manner to evaluate the effect of mobility control agents on this process. 

Results of Immiscible Displacement Tests. The results of the tests show that immiscible carbon dioxide flooding followed by waterflooding is effective in increasing the oil recovered from a core. The oil recovered by a conventional waterflood was equal to about 30.4% of a pore volume, PV. Immiscible carbon dioxide flooding increased the recovery to a total of 50.5% PV. The addition of a mobility control agent increased the recovery further to 58.3% PV this amounts to 39% additional tertiary oil due to the effectiveness of the mobility control in the carbon dioxide immiscible process. 

It is apparent that the addition of the mobility control agent did not affect the miscibility process, as evidenced by the comparable oil recovery to that of the no mobility control case. At the same time the mobility of carbon dioxide was decreased more than twenty-fold. This important flnding demonstrates that the mobility control method produces effective mobility control without adversely affecting the miscible recovery mechanism. 

Castor, T.P., Edwards, J.B., Passman, E.J., 1981a. Response of mobility control agents to shear, electrochemical, and biological stress. In Shah, D.O. (Ed.), Surface Phenomena in Enhanced Oil Recovery. Plenum, pp. 773—820. 

All the polymers that have been suggested as mobility control agents are pseudoplastic, i.e., they are shear-thinning. The extent of pseudo-plasticity is different for polyacrylamides, polysaccharides, and hydroxy ethyl cellulose. Viscosities of these polymers are plotted against shear rate in Figure 12. One model that describes the shear-thinning behavior observed is the Ost-wald-de Waele relationship ... 

This section describes foam and the variety of foams that are useful as C02 mobility-control agents. 

Molybdenum trioxide mobility control agent, waterflooding enhanced oil recovery Acrylamide... 

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