1. Simulation run and History-Matching with CMOST
  2. Oil saturation images/maps at different stages of simulation
Core-scale simulation runs were conducted to investigate the potential of secondary and tertiary recovery processes in qualitative aspects. Based on history matching of experimental data conducted during different flooding techniques, maps showing oil saturation (soi) were generated at different time intervals, as presented in Figs. 9(a), 9(b) and 9(c). As mentioned earlier, case scenarios I, II and III refer to flooding studies in the presence of {0.10% 14-6-14 GS}, {0.10% 14-6-14 GS + 0.05% PHPA} and {0.10% 14-6-14 GS + 0.05% PHPA +0.025% SiO2} respectively. At initial time (t = 0), the porous rock model was saturated with crude oil. At this stage, initial oil saturation (soi) percentages were measured as 79.76% for case I, 80.08% for case II, and 80.25% for case III. This represents the original oil in place (OOIP). In each case scenario, same brine solution containing 1.0% NaCl was injected at constant flow rate (0.00024 m3/day or 10 ml/h) as a form of secondary recovery process. During this process, the oil saturation within porous model gradually decreased over time [17,27,64]. This is evident from the evolution of Cartesian grid images from brown/red (previously) to a yellow/green hue, which is indicative of decreasing oil saturation. For case I, oil saturation values decreased from 79.76% (initial time) to 59.12%, 53.44% and 43.97% at the end of 30 min, 60 min and 208 min respectively. Similarly, respective oil saturation percentages after 30, 60 and 208 min were observed to be 59.78%, 54.13% and 44.69% for case II; and 59.79%, 54.07% and 44.35% for case III. Time-dependent data at 208 min represents the end of secondary (water-flood) recovery. It is pertinent to note that water-flooding exhibited oil saturation levels in the 43-45% range, thereby resulting in similar saturation profiles. However, main findings of the study lie in the evaluation of enhanced oil recovery results, during which {aqueous chemical fluid + chase water} were injected successively [18,64,65]. Aqueous chemical flooding was introduced at the onset of 208 and was stopped at 294 min. During the 86 min time-period of the first stage of EOR, oil saturation percentages were found as 36.93%, 35.62% and 35.06% for cases I, II and III respectively. This was followed by chase water (with 1.0% NaCl) injection until a cumulative time-period of nearly ~7 h 22 min, wherein the residual oil saturation (sor) was investigated. The sor values corresponding to I, II, and III were determined from history-match results as 31.96%, 30.68% and 29.30% respectively. In summary, analyses of oil saturation profiles prove that analyzed chemical fluids improve the sweep efficiency by moving the oil far away from the injector well, and extract oil from producer well.