Pore-scale imaging and analysis of secondary surfactant flooding in a heterogeneous carbonate rock
File(s)
Published version
Author(s)
Alzahrani, Hussain M
Bijeljic, Branko
Foroughi, Sajjad
Blunt, Martin J
Type
Journal Article
Abstract
We investigate if improved oil recovery by surfactant injection in carbonate rocks is caused by the interplay of wettability alteration from oil-wet to mixed-wet conditions and reduced interfacial tension (IFT). High-resolution micro-CT imaging coupled with high-pressure and temperature flow apparatus were used to investigate fluid displacement, oil recovery, pore and throat occupancy, and to quantify in situ changes in wettability when the surfactant was injected. We used a concentration of cationic surfactant above the critical micelle concentration, CMC, with no co-solvent, with a resultant oil/water interfacial tension which although lowered to 6.3 mN/m, was not negligible. The rock sample underwent crude oil injection for 3 weeks at a high temperature to reach a representative reservoir wettability state. Then, the surfactant was injected as a secondary recovery method. The phase behaviour and nature of any emulsion formed was also quantified. The surfactant recovered a remarkable 79% of the initial oil. Analysing pore and throat occupancy revealed an initially oil-wet system. The surfactant first invaded and displaced oil from medium-sized and large pores with radius greater than 15 μm, with minimal impact in small pores. While subsequent injection further recovered oil from smaller pores, the tiniest ones, with radii smaller than 5 μm, remained unaffected. In addition, observations of contact angles, mean curvatures and capillary pressures indicated a transition from a weakly oil-wet to a mixed-wet state throughout surfactant injection. The analysis confirmed that a combination of wettability alteration and lowered IFT leads to improved recovery.
Date Issued
2025-05-01
Date Acceptance
2025-01-26
Citation
Geoenergy Science and Engineering, 2025, 248
ISSN
2949-8910
Publisher
Elsevier
Journal / Book Title
Geoenergy Science and Engineering
Volume
248
Copyright Statement
© 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Subjects
Carbonate reservoirs
CONTACT-ANGLE
EMULSIFICATION
Energy & Fuels
Engineering
Engineering, Petroleum
Enhanced oil recovery
ENHANCED OIL-RECOVERY
Interfacial tension
Micro-CT imaging
MICROEMULSIONS
SALINITY
Science & Technology
SPONTANEOUS IMBIBITION
Technology
TENSION
WATER
WET
Wettability alteration
WETTABILITY ALTERATION
Publication Status
Published
Article Number
213728
Date Publish Online
2025-01-31