Injection Well Stimulation with Micellar Solutions
Authors: Gogarty W.B. , Kinney W.L. , Kirk W.B. 
Published: December 2007

Laboratory and field tests show that micellar solutions are effective in stimulating injection wells. Wellbores are effectively cleaned, skin damage is reduced, and rates of water injection at constant pressure are increased by as much as 368 percent.

Introduction
Fundamental to the waterflood process is that water be injected into the reservoir through numerous wells. It is critical, also, to maintain the injection capabilities of the wells over the life of the project. Many well known techniques, such as fracturing and acidizing, have been developed over the years to achieve this result and are common in most waterflood operations. One limitation on the water injection capacity of a well is the residual oil saturation in the vicinity of the wellbore. Techniques have been described in recent years for removing this residual oil, thus increasing the water injection capability. Micellar solutions have been tried as injection well stimulants to see if changes in relative permeability could be obtained by injecting small volumes of these fluids. We shall present here the results of two field testing programs, as well as theoretical aspects and laboratory data supporting the conclusion that micellar solutions do indeed improve injection well capabilities. Patents defining injection well stimulation with micellar solutions have been issued, and this technology has been licensed to Dow Chemical Co., who make it commercially available through their Dowell Div. In their development program they have treated more than 100 wells, most of them randomly selected from many different sandstone reservoirs. By using the micellar solutions, Dowell successfully stimulated 72 percent of the 90 wells in sandstone reservoirs. (Ref. 5 describes the results from some of the treatments.) Development in carbonate reservoirs is now under way.

Well Stimulation Benefits
Laboratory studies in conjunction with theoretical studies indicate the injectivity improvements that will occur from well stimulations with micellar solutions. Both types of results are presented in this section. The theoretical results are based on a computer model study of a repeated five-spot pattern. Cores and fluids from reservoirs in the Big Horn basin of Wyoming were used to obtain the laboratory results.

Model Studies
In the model studies, injectivities were calculated by using the Higgins-Leighton approach for a waterflood. Well stimulation was accounted for by reducing the oil saturation to zero at various radii (depth of treatment) from the wellbore. The relative permeability to water was taken as 1 from the sandface in the permeability to water was taken as 1 from the sandface in the well to the indicated radius. Calculations were based on a net pay thickness of 1 ft, with a permeability and porosity of 229 md and 20 percent, respectively. A porosity of 229 md and 20 percent, respectively. A 10-acre repeated five-spot pattern was used in these studies. Saturations before waterflooding were taken as 80 percent oil and 20 percent water. The relative permeability curves used in the calculations are shown permeability curves used in the calculations are shown in Fig. 1. Mobility values were determined with the curves, using a water viscosity of 1 cp and oil viscosities of 7, 14 and 28 cp. Printout from the Burroughs 5500 computer program of the Higgins-Leighton model gives the injection rate as a function of the pore volume of water injected. Calculations were made with a constant pressure differential between injection and producing wells.
JPT
P. 1577