Experimental investigation of the effect of water-based drilling mud on the wettability of dolomite in contact with CO2 and hydrogen
Author Identifier (ORCID)
Alireza Keshavarz: https://orcid.org/0000-0002-8091-961X
Abstract
Wettability governs multiphase flow, trapping and leakage risk in subsurface hydrogen (H2) and carbon-dioxide (CO2) storage. Yet little is known about how drilling-fluid filtrates modify rock–fluid–gas interactions under storage conditions. This study quantifies the impact of a conventional water-based mud (WBM) (hereafter Base Mud) and a poly-vinyl-alcohol (PVA) nanomodified WBM (hereafter PVA Mud) on the wettability of dolomite, a representative carbonate reservoir mineral. Dolomite slabs were aged for 3 and 12 weeks at 30 °C in either base or PVA Mud, then placed in a high-pressure captive-bubble cell. Static contact angles between water and H2 or CO2 were measured across a range of pressures. All tests included 500 psi (3.4 MPa) and 1500 psi (10.3 MPa), with maximum pressures reaching 2000 psi (13.8 MPa) for CO2 and 2500 psi (17.2 MPa) for H2.Each datum is the mean of three replicates (±4°). Clean dolomite was strongly water-wet, exhibiting contact angles of 16–18° for H2 and 18–20° for CO2. Aging in base mud induced a pronounced CO2–mud synergy: after 12 weeks the CO2/water angle rose to 39–41°— ∼20° above the pristine value—while the H2 angle increased more modestly to 26–29°. Regression analysis confirmed a strong pressure dependence for CO2 in base mud (R2 = 0.933) but the small sample size limited statistical significance (p = 0.167, n = 3). In contrast, the PVA-modified mud damped the CO2 shift (28–30°) yet, over the same aging period, allowed H2 angles to climb to 36–38°, indicating progressive polymer adsorption that preferentially affects H2 wettability. Across all scenarios the angles remained below 45°, so the rock stayed nominally hydrophilic, but even these moderate increases may lower capillary entry pressures and reduce storage security. The results provide the first systematic database of H2- and CO2-water contact angles on mud-aged dolomite. They show that (i) drilling mud chemistry can differentially alter carbonate wettability to each gas, (ii) base WBM promotes a stronger hydrophobic shift in the presence of CO2, whereas (iii) PVA nanomodification offers a more balanced, pressure-insensitive response. These insights help refine mud-system selection and near-wellbore management strategies for emerging H2 and CO2 geo-storage projects.
Keywords
Carbon dioxide, contact angle, dolomite, hydrogen, polyvinyl alcohol, water-based mud
Document Type
Journal Article
Date of Publication
4-23-2026
Volume
228
Publication Title
International Journal of Hydrogen Energy
Publisher
Elsevier
School
School of Engineering
Copyright
subscription content
Comments
Safari, R., Aghaei, H., Shahsavani, B., Toorajipour, A., Darzi, H. H., & Keshavarz, A. (2026). Experimental investigation of the effect of water-based drilling mud on the wettability of dolomite in contact with CO2 and hydrogen. International Journal of Hydrogen Energy, 228, 154690. https://doi.org/10.1016/j.ijhydene.2026.154690