جستجوی مقالات مرتبط با کلیدواژه « Enhanced Oil Recovery » در نشریات گروه « برق »

Low salinity water (LSW) flooding is one of the emerging EOR methods which has recently attracted lots of attention. Wettability alteration from oil-wet to water-wet triggered by ion exchange between low salinity water and rock surface is one of the dominant mechanisms to increase oil recovery by LSW. This paper studied the performance of LSW flooding in a sandstone oil reservoir where wettability alteration was investigated by coupling two-phase flow equations and geochemical reactions between water and rock surface. A wettability alteration index based on the ion equivalent fraction of sodium was introduced that mainly consists of the effects of ion exchange and clay properties on oil/water relative permeability functions. Also, the effect of calcite mineral dissolution was investigated by the relevant geochemical reactions. Results showed that salinity difference between injected and formation water caused ion exchange processes between water and rock surface. Also, calcite dissolution enhanced ion exchange processes and thus led to wettability alteration to more water-wet conditions. Results showed that the presence of dissolved CO2 in water increased the rate of calcite dissolution. It was also found that the rate of ion exchange and calcite dissolution reactions decreases far from the injection well. The results of this study revealed that LSW flooding provided incremental oil recovery of 8% of the oil initially in place as compared to high salinity water flooding.

According to the positive results of low salinity water (LSW) flooding to recover incremental oil, different studies have been performed to investigate the combination of LSW and other enhanced oil recovery (EOR) methods. Combination of polymer flooding and LSW could be one of the most effective EOR methods. Taking into account the strength and weakness of each individual method, one can take advantage of the synergism between polymer and LSW: presence of polymer improves oil sweep efficiency and LSW decreases polymer adsorption and alters rock wettability to more water-wet. In this paper, we applied fractional flow theory to investigate the performance of polymer-associated low salinity water (LSP) flooding as an EOR method in sandstone reservoirs. Also, application of LSP flooding to recover incremental oil was compared to that of high and low salinity water flooding. The results showed that as LSP was injected into the given sandstone reservoir, there is a delay in water breakthrough time to as much as 0.75 PV. Also, oil recovery duet to the LSP injection increased from 38% to 77% as compared to high salinity water flooding after 1 PV injection. Fractional flow analyses showed that the incremental oil obtained by LSP is mainly due to the presence of two distinct water saturation shock front.