Suitability of ionic solutions as a chemical substance for chemical enhanced oil recovery – A simulation study

Abstract

Surfactant flooding is one of the important methods applied in chemical enhanced oil recovery (CEOR). Toxicity, high cost, and degradation at harsh conditions are the main issues that face companies during surfactant flooding process. Ionic liquids (ILs), known as liquid organic salts at ambient condition, have been suggested as alternative chemicals due to their superiority over the conventional surfactants. In this paper, we report simulation of core flooding experiments conducted using ionic liquid (Ammoeng 102) on Berea sandstone core samples to study efficiency of the IL on oil recovery. The core flooding experiments were published elsewhere (BinDahbag et al., 2014, 2015). The experiments were simulated using surfactant flood model (SFM), accessible in CMG STARS software. The measured oil recovery and pressure drop were utilized to history match the core flood experiments. First scenario was simulated by injecting 20 wt% salinity brine (83% sodium chloride, NaCl, and 17% calcium chloride, CaCl2) into a core sample initially saturated with 26% irreducible water saturation (Swirr) of the same brine to recover 43% of the original oil in place (OOIP) followed by the ionic solution flooding to recover more than 5% of the OOIP. To study the effect of Swirr on oil recovery using ionic solution, the second scenario was simulated similar to the first one in terms of the injected liquids and sequence except the irreducible water saturation (34% compared to 26%). About 38% of the OOIP was produced during brine flooding whereas more than 6% of the OOIP oil was recovered during ionic solution flooding. To study the effect of brine salinity on oil recovery, a third scenario similar to first one except salinity of brine (10% instead of 20 wt%) was simulated. The result for the third scenario shows recovery of 53% of the OOIP throughout brine flooding followed by 2% incremental recovery during the ionic solution flooding. The results demonstrate that the effect of irreducible water saturation is important during brine flooding stage; however, it is insignificant during ionic solution flooding stage for the runs conducted in this study. In addition, low salinity brine flooding results in higher oil recovery, however, ionic solution flooding was more efficient at higher salinity environment. Simulation of all scenarios showed an acceptable agreement between the experimental and simulation oil recoveries. However, the simulation pressure drops were not matched with the experiments. This may be possible by including the well parameters into the sensitivity analysis. Nevertheless, this has not been conducted in order to isolate the impact of well parameters on the estimated relative permeability parameters.