Application of alkali-surfactant-polymer ASP flooding for improving viscous oil recovery from Alaskan north slope reservoir

Alkali-surfactant-polymer (ASP) flooding is a chemical EOR method that can be used to improve recovery of heavy oil containing organic acids by increasing sweep efficiency, and reducing interfacial tension. Typically, ASP flooding is followed by extended waterflooding. The concentration of alkali, surfactant, and polymer used in the process depends on oil type, connate water salinity, pressure and temperature of the reservoir, and injection water quality. In this study, an ASP flood was designed to optimize the concentration of alkali, surfactant, and polymer for an Alaskan reservoir using a reservoir simulation model. Also, the effects of waterflooding and improvement with ASP flooding were evaluated and compared. Based on literature review and previously published screening criteria, the Western North Slope (WNS) 1 reservoir was selected for application of the ASP process and a simulation model for this reservoir was generated with 5-spot flood pattern. Reservoir fluid properties were modeled through regression analysis of actual field data. Simulation runs conducted for primary and waterflooding processes showed that the recovery factor increased from 3% due to primary recovery to 45% due to waterflooding at 500 psi drawdown for 60 years with a constant producing gas oil ratio (GOR). ASP flooding was conducted to increase recovery further, and optimum ASP parameters were calculated for maximum recovery. Also, effect of alkali, surfactant and polymer on recovery was observed and compared with ASP flood. If proved effective, the use of ASP chemicals for Alaskan North Slope (ANS) reservoirs to increase the recovery factor could supplement current miscible gas injection with chemical EOR. It will help to develop chemical flooding processes for heavier crude oil produced in harsh environments and create new horizons for chemical industries in Alaska.