Wettability Alteration Mechanism for Oil Recovery from Fractured Carbonate Rocks

• Published in: Transport in porous media Vol. 87; no. 2; pp. 635 - 652
• Main Authors: Gupta, R., Mohanty, K. K.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.03.2011; Springer; Springer Nature B.V
• Subjects: Alterations; Calcite; Calcium ions; Carbonate rocks; Civil Engineering; Classical and Continuum Physics; Contact angle; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Electrolytes; Ethoxylation; Exact sciences and technology; Geotechnical Engineering & Applied Earth Sciences; High temperature; Hydrocarbons; Hydrogeology; Hydrology/Water Resources; Imbibition; Industrial Chemistry/Chemical Engineering; Limestone; Magnesium; Oil recovery; Optimization; Plates; Salinity; Sedimentary rocks; Surfactants; Wettability; United States; Texas; Imbibition; Wettability alteration; Anionic surfactants; Optimal salinity; Divalent ions; Fractured carbonates; reservoir rocks; carbonate rocks; reservoirs; calcite; recovery; electrolytes; North America; drill cores; limestone; magnesium ion; temperature; wettability; petroleum; models; salinity; hydrocarbons; calcium ion; magnesium; concentration; transport; carbonates; high temperature; sulfate ion; fractured environment; sedimentary rocks; alteration; porous media
• ISSN: 0169-3913; 1573-1634
• DOI: 10.1007/s11242-010-9706-5

Oil can be recovered from fractured, initially oil-wet carbonate reservoirs by wettability alteration with dilute surfactant and electrolyte solutions. The aim of this work is to study the effect of salinity, surfactant concentration, electrolyte concentration, and temperature on the wettability alteration and identify underlying mechanisms. Contact angles, phase behavior, and interfacial tensions were measured with two oils (a model oil and a field oil) at temperatures up to 90°C. There exists an optimal surfactant concentration for varying salinity and an optimal salinity for varying surfactant concentration at which the wettability alteration on an oil-aged calcite plate is the maximum for anionic surfactants studied. As the salinity increases, the extent of maximum wettability alteration decreases; also the surfactant concentration needed for the maximum wettability alteration decreases. IFT and contact angle were found to have the same optimal salinity for a given concentration of anionic surfactants studied. As the ethoxylation increases in anionic surfactants, the extent of wettability alteration on calcite plates increases. Wettability of oil-aged calcite plates can be altered by divalent ions at a high temperature (90°C and above). Sulfate ions alter wettability to a greater extent in the presence of magnesium and calcium ions than in the absence. A high concentration of calcium ions can alter wettability alone. Magnesium ions alone do not change calcite plate wettability. Wettability alteration increases the oil recovery rate from initially oil-wet Texas Cordova Cream limestone cores by imbibition.