Geochemical Modelling of Carbonated Low Salinity Water Injection CLSWI to Improve Wettability Modification and Oil Swelling in Carbonate Reservoir

Abstract

Conventional carbonated water injection (CWI) induces oil swelling and reduction of oil viscosity and density. The CO2 solubility in carbonated water is a key factor to determine these effects and is sensitive to pressure, temperature, and salinity. The CWI has another aspect of CO2 storage due to solubility trapping mechanism. Low saline water is a favorable condition to solubilize CO2 into brine due to salting-out phenomenon. As well, the low saline water injection (LSWI) has potential to enhance oil recovery originated from wettability modification in a carbonate reservoir. In terms of geochemical aspect, low saline brine introduces higher CO2 solubility and wettability modification effect. It has triggered the evalution of hybrid process, which integrates LSWI with CWI. The CO2 dissolution and wettability modification effects are highly related to geochemical reactions in brine/oil/rock system. This study has constructed the numerical modelling of carbonated low salinity water injection (CLSWI) coupled with geochemical reaction and evaluated the performance in terms of oil production and CO2 storage. In core and pilot systems, the wettability modification effect of CLSWI contributes to 9% and 15% increased oil recovery over CSWI. In both systems, more CO2 has been captured up to 17% and 45% due to salting-out phenomenon, respectively. CLSWI enhancing oil swelling and oil viscosity reduction has also improved injectivity up to 31% over CSWI in pilot system. The results from this study has demonstrated that CLSWI is a promising water-based hybrid EOR.

Mechanistic study of the carbonated smart water in carbonate reservoirs

“…10,11 CLSW takes advantage of the high CO 2 solubility in the low salinity water (salting-in phenomenon), which ensures a high mass transfer of CO 2 from the CW to the oil, based on 3-7 times higher affinity of CO 2 to be dissolved in oil than in water. [3][4][5] CW had an enhanced sweep efficiency compared to the other CO 2 -EOR methods such as CO 2 injection and water-alternating-gas (WAG) due to oil viscosity reduction and CW's ability to overcome the shielding effect. 6,12 The shielding prevents the CO 2 (free phase) from being in contact with the oil, but in the carbonated water, the CO 2 is dissolved in the water as an aqueous phase.…”

“…20 In the CLSW injection, some experiments showed that up to 17-45% CO 2 volume was captured in the formation due to the salting-in phenomenon. 5 When the CO 2 is dissolved in the water, water will have lower mobility due to the higher viscosity. Therefore, the stored CO 2 in the remaining water will eliminate the risk of buoyancy-driven leakage, thus securing storage.…”

“…UTCOMP simulator was recently developed by the University of Texas at Austin (Sanaei et al, 2019). Lee et al 5…”

“…Original Research Article: Mechanistic study of the carbonated smart the formation. [3][4][5] One of those cooptimization methods is carbonated water (CW) injection, where the injected water is enriched with CO 2 at the surface and injected as one fluid. However, CW injection proved significant in the enhancement of the oil recovery and typical decrease in the residual oil saturation over the traditional seawater injection.…”

“…The limited published studies regarding carbonate water in carbonate reservoirs are mainly related to experimental and modeling core data, where the fractures are not considered. 5 Besides, the low salinity water used in the previous studies are based on the dilution of formation or sea water. Therefore, further studies are required to examine the fracture effect and related mechanisms on the process' overall performance and the low salinity water composition.…”