Surfactant-Polymer Flooding: Chemical Formulation Design and Evaluation for the Raudhatain Lower Burgan RALB Reservoir in Kuwait

Abstract

Abstract Surfactant-Polymer (SP) flooding is an Enhanced Oil Recovery (EOR) process that can lead to incremental oil recovery through two mechanisms: reducing oil/water interfacial tension (IFT) to decrease residual oil saturation and increasing the viscosity of the displacing fluid to improve overall sweep efficiency. IFT reduction allows better oil recovery by overcoming capillary effects while the increased viscosity of the displacing fluid allows a more homogeneous sweep of reservoir oil. Implementing chemical flooding in reservoirs with relatively high temperature and in-situ salinity (> 200 g/L) is somewhat challenging. This paper describes the extensive laboratory work performed for the light oil Raudhatain Lower Burgan (RALB) reservoir (180°F/82°C) in Kuwait. Reservoir fluids were thoroughly characterized to preselect the most suitable chemicals for the SP process. Reservoir crude oil was analyzed and recombined with gases (C1-C3) based on reported Gas-to-Oil (GOR) ratio to reproduce the oil in-place at original reservoir conditions in terms of pressure, temperature and oil composition. A shift of the live oil Equivalent Alkane Carbon Number (EACN) was noticed compared to dead oil EACN. Numerous surfactants were screened based on three main criteria: solubility in the envisioned injection brine, ultra-low oil/water interfacial tension and chemical adsorption on reservoir rock. Different brine types were considered and the use of adsorption inhibitors was also investigated. Furthermore, polymer screening, involving temperature resistant polymers, was conducted by means of viscosity, long-term aging and adsorption tests. Polymer compatibility with the selected surfactants was also evaluated. The selected SP formulation was further evaluated through a series of coreflood experiments mainly based on chemical adsorption on reservoir rock and incremental oil recovery and an injection strategy was designed thereof. Laboratory results obtained thus far are encouraging and provide a systematic methodology to design surfactant-polymer injection in high temperature, high salinity and light oil reservoirs that are similar to the RALB reservoir. Additional techno-economic evaluation is in progress in preparation for field-scale deployment of surfactant polymer injection at the RALB reservoir in Kuwait.