Enhanced oil recovery, application

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. 

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). 

In 1988, Terry and coworkers attempted to homopolymerize ethylene, 1-octene, and 1-decene in supercritical C02 [87], The purpose of their work was to increase the viscosity of supercritical C02 for enhanced oil recovery applications. They utilized the free radical initiators benzoyl peroxide and fert-butyl-peroctoate and conducted polymerization for 24-48 h at 100-130 bar and 71 °C. In these experiments, the resulting polymers were not well studied, but solubility studies on the products confirmed that they were relatively insoluble in the continuous phase and thus were not effective as viscosity enhancing agents. In addition, a-olefins are known not to yield high polymer using free radical methods due to extensive chain transfer to monomer. 

Although the contacting experiments were performed with surfactant systems typical of those used in enhanced oil recovery, application of the results to detergency processes may be possible. For example, the growth of oil-rich intermediate phases is sometimes a means for removing oily soils from fabrics. Diffusion path theory predicts that oil is consumed fastest in the oil-soluble end of the three-phase regime where an oil-rich intermediate microemulsion phase forms. 

FIGURE 20.2-4 Schematic representation of enhanced oil recovery application of membranes for COj-CRi separation from gas recovery from a production well after injection of CO ,... 

Many of the important applications for the separation of COj and CH correspond to C02 partial pressures well above 20 aim (e.g., cases 1-3 in the previous discussion of enhanced oil recovery applications). In such cases, competiiiou for umelaxed volume should be of recond-order importance, since the condensable" nature of C02 causes it to dominate the microvoid environments in the polymer even in the face of substantial methane panial pressures. At high COj partial pressures, plasticizing behavior nich as that illustrated in Fig. 20.4-4 may he obeerved. On the other hand, at relatively low C02 pressures (20 atm) (cases 4 and 5 in the discussion of enhanced oil recovery applications), competition effects would be anticipated for most glassy polymers. These effects could be mesked in the case of cellulose acetate because or iis strong tendency to internet with C02 and exhibit plasticization at low penial pressures. 

S. Linder, Ph.D, Dissertation, "Solution Properties of Water Soluble Macromolecules for Enhanced Oil Recovery Applications, Mississippi State University (1985). 

Unsal, E., Evaluation of Flow Properties of Dilute Aqueous Polymer Solutions For Enhanced Oil Recovery Applications, Ph.D. thesis, the Pennsylvania State University (1978). 

Surfactants are used extensively in enhanced oil recovery. Applications include micellar floods or flooding in conjunction with polymers, alkalis, steam or carbon dioxide. Another apphcation is the generation of foams for mobility control or blocking and diverting. For each of these applications care must be taken in selecting the surfactants. Surfactants tend to be a major portion of the costs associated with FOR, and losing surfactant to adsorption leads to substantial economic losses. 

A highly active bactericide for oil field drilling and completion fluids, fracturing fluids and enhanced oil recovery applications. 

Pengrowth has targeted East Bodo (Alberta side) and Cosine (Saskatchewan side) for waterflood optimization and subsequent enhanced oil recovery applications. Currently, the most practical EOR technology for this heavy oil reservoir seems to be the polymer flood technology in combination with horizontal weUs. Several investigatorsri-4) have demonstrated the potential of the polymer flood fechnology for improved oil recovery in heavy oil reservoirs. 

---