- Simulation run and History-Matching with CMOST
- 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.