Field Pilot Test Results for a Permeability Modification Treatment Using a Gelled Surfactant Chemical System
Authors: Gall Bonnie , Dobson Randy , Llave Feliciano , Bryant Rebecca , French Troy , Stafford Mike 
Published: December 2007

Bonnie Gall, BDM-Petroleum Technologies; Randy Dobson, Sr., Akzo Nobel Chemical Co., Feliciano Llave, SPE, Associated Western Universities; Rebecca Bryant, SPE, BDM-Petroleum Technologies; Troy French, SPE, BDM-Petroleum Technologies; Mike Stafford, SPE, RDT Properties, Inc.

Abstract
Four injection wells in the Plant #5 area of the Cushing Field Bartlesville Sand Waterflood project, Creek Co., OK, were treated with a surfactant/alcohol chemical system for in-depth permeability modification. The objectives of this treatment were to plug a well-swept, high permeability zone and to divert injected water into unswept portions of the reservoir.
The chemical system is designed with low viscosity for easy injection in the wellbore region. As alcohol and surfactant chromatographically separates in the reservoir, a highly viscous surfactant gel forms at some depth from the wellbore The depth of injection can be controlled by the amount of alcohol injected with the surfactant. This highly-salt-tolerant chemical system is not environmentally hazardous and requires minimal on-site injection equipment.
A tracer survey was conducted in May 1995, followed by injection of the chemical system in November 1995. Economic evaluation of the treatment indicated that the chemical costs were within 5 to 6 months payout based on an increase in incremental oil production. The oil production decline for the unit has been altered. In addition, the oil production pattern has been altered. Production in the principle flow direction before the treatment has declined, and production in offset wells has increased. Effects of the treatment can be observed up to 15 months after the test.

Introduction
Reservoir heterogeneities can affect sweep efficiency of oil recovery processes. Significant effort has been expended to develop methods to reduce permeability in high permeability zones, thereby forcing sweep fluid to contact and produce bypassed oil in the reservoir.
Emphasis has been placed on polymer systems that develop high viscosity using delayed crosslinking chemistry to create gels in situ. The chemistry and kinetics of these systems are complex. Technical difficulties can include: loss of injectivity; failure to propagate the chemicals far enough into the reservoir. control of the kinetics of gelation; adverse reservoir conditions such as excessive shear or salinity; or environmental concerns associated with toxic crosslinking agents.
Surfactant/alcohol chemical systems have been developed to provide low viscosity fluids for easy handling and injection in the field. These mixtures separate in the reservoir, leaving high viscosity chemicals in the more permeable matrix. Subsequent water injection fluids can then be diverted to zones of lower permeability and higher oil saturation. Laboratory evaluation of these systems has been described previously. A single well treatment was conducted in the Stone Bluff field, Wagoner Co., Oklahoma. Results indicated that the waterflood injection profile was altered by the treatment, and a slight decline in water production was observed. Production operations in the field were discontinued, however, before long term effects could be evaluated.
These results suggested that multi-injector treatments would be required to evaluate in-depth surfactant/alcohol permeability modification systems for fluid diversion and oil production. This paper will describe pre-test characterization of the reservoir, treatment design, injection procedures, and post-test production monitoring for an in-depth profile modification treatment of 4 injection wells in the Cushing Field in Creek Co., Oklahoma.
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