Ion Chromatography Analysis of Advanced Ion Management Carbonate Coreflood Experiments

Abstract

Abstract Advanced Ion Management (AIM) is an enhanced oil recovery (EOR) process where waterflood injection water is modified by the addition, removal, or dilution of ions. AIM can yield an increase in oil recovery compared to waterflooding using formation brines. To better understand the oil recovery mechanism of AIM in carbonates, ion chromatography studies and salt solubility measurements were conducted on AIM brines used in floods of Middle Eastern core. The ion composition of the brines – upon mixing after extended time, at reservoir temperature and pressure, and after core flooding - were compared to elucidate the ion composition changes during an AIM waterflood and how those changes could lead to additional oil recovery. That knowledge could potentially be used to screen reservoir rock types and available water sources to determine which would be best suited for EOR from AIM waterflooding. AIM technology encompasses a wide range of injection brines, and thus this ion chromatography analysis covers a range of modified brines, including brines for which analyses have not been previously published. Analysis of the results has implications for how ion composition may be correlated with oil recovery and what facilities are required to obtain the desired composition. The study finds that neither rock dissolution nor ion exchange alone is sufficient to explain oil recovery with modified brine injection, and neither mechanism is a guarantee of additional oil recovery. It also finds that sodium phosphate, borax, and sodium sulfate all precipitate divalent cations from seawater at field operating conditions.