Abstract
Carbonated water injection (CWI) induces oil swelling and viscosity reduction. Another advantage of this technique is that CO2 can be stored via solubility trapping. The CO2 solubility of brine is a key factor that determines the extent of these effects. The solubility is sensitive to pressure, temperature, and salinity. The salting-out phenomenon makes low saline brine a favorable condition for solubilizing CO2 into brine, thus enabling the brine to deliver more CO2 into reservoirs. In addition, low saline water injection (LSWI) can modify wettability and enhance oil recovery in carbonate reservoirs. The high CO2 solubility potential and wettability modification effect motivate the deployment of hybrid carbonated low salinity water injection (CLSWI). Reliable evaluation should consider geochemical reactions, which determine CO2 solubility and wettability modification, in brine/oil/rock systems. In this study, CLSWI was modeled with geochemical reactions, and oil production and CO2 storage were evaluated. In core and pilot systems, CLSWI increased oil recovery by up to 9% and 15%, respectively, and CO2 storage until oil recovery by up to 24% and 45%, respectively, compared to CWI. The CLSWI also improved injectivity by up to 31% in a pilot system. This study demonstrates that CLSWI is a promising water-based hybrid EOR (enhanced oil recovery).
Highlights
Waterflooding has been deployed to pressurize depleted reservoirs for oil recovery when primary recovery becomes inefficient
This study assessed the performance of hybrid carbonated low salinity water injection (CLSWI) in terms of oil production and CO2 storage
The process behind hybrid CLSWI depends on geochemical reactions in the brine/oil/rock system
Summary
Waterflooding has been deployed to pressurize depleted reservoirs for oil recovery when primary recovery becomes inefficient. Economic and practical enhanced oil recovery (EOR) technologies have been developed to recover the oil remaining after waterflooding. One such technique is carbonated water injection (CWI), which is CO2-enriched waterflooding. When carbonated water (CW) comes into contact with oil, the CO2 dissolved in CW moves into the oil, resulting in oil viscosity reduction and swelling [1] These effects depend on the CO2 solubility of brine. The CWI phenomenon has been visualized in glass micromodels [1, 3, 4] These studies confirmed oil swelling, oil viscosity reduction, and the generation of CO2enriched gas during CWI. Sohrabi et al [1] and Kechut et al [4] have conducted coreflooding experiments to observe whether oil production is enhanced and performed numerical simulations
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