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- Title
Enhanced oil recovery via dissolution of low molecular weight PDMS in CO2 during immiscible gas injection in matrix-fracture system.
- Authors
Gandomkar, Asghar; Torabi, Farshid; Enick, Robert M.
- Abstract
Oil recovery in natural fracture reservoirs can be improved by reducing the capillary force during the gravity drainage process in matrix-fracture system. In the current study, a modified gas was generated via dissolution of low molecular weight poly(dimethyl siloxane) (PDMS, average M w 3780 g/mol, 10000 – 50000 ppm) in CO 2 to enhance oil recovery at 50 °C or 70 °C and 3000 psi. Cloud point measurements indicated that PDMS dissolved in CO 2 at pressures less than 3000 psi, which was below the minimum miscibility pressure (MMP) of ∼3600 psi at 70 °C determined with the vanishing interfacial technique. The solution density increased from 669.6 kg/m3 for pure CO 2 to 780.3 kg/m3 for CO 2 /PDMS (50000 ppm) at 70 °C and 3000 psi, thereby reducing the density difference between the CO 2 -rich fluid and crude oil (ρ o =865.2 kg/m3) in matrix-fracture system. Also, CO 2 -oil interfacial tension (IFT) was reduced from 65 to 15 dyn/cm via the dissolution of 50000 ppm PDMS in CO 2. Therefore, it led to the CO 2 diffusion coefficient increased in both reservoir-fluid saturated porous media and bulk oil scenarios 3–4 fold and 4–7 fold respectively in comparison to pure CO 2 injection. These PDMS-induced changes reduced the capillary effects in gas-invaded zone, which consequently led to an increase in oil recovery of 25% points (from 31% to 56%) compared to pure CO 2 injection in the case of capillary continuity during gravity drainage tests. For the field-scale, because the PDMS can dissolve in CO 2 at pressures and temperatures which are commensurate with CO 2 EOR, it is a promising CO 2 -philic chemical for increasing CO 2 density and improving CO 2 diffusion coefficient in gas invaded zone compared to conventional CO 2 injection. • The effect of CO 2 -soluble polymers on oil recovery in gas invaded zone. • PDMS is soluble in CO 2 at pressure commensurate with CO 2 -EOR. • The density difference reduced in matrix-fracture system during CO 2 /PDMS injection. • The gas diffusion coefficients increased (4-7 fold) during CO 2 /PDMS injection. • 25% additional oil recovery was achieved during CO 2 /PDMS in the gas invaded zone.
- Subjects
ENHANCED oil recovery; GAS injection; MOLECULAR weights; POROUS materials; CARBON dioxide
- Publication
Chemical Engineering Research & Design: Transactions of the Institution of Chemical Engineers Part A, 2024, Vol 203, p18
- ISSN
0263-8762
- Publication type
Article
- DOI
10.1016/j.cherd.2024.01.022