Rock Wettability Control and Chemical Loss Reduction in EOR Process
Lu, Shaohua1, Ponisseril Somasundaran1 (1) Columbia University, New York, NY
Chemical reagent loss due to adsorption and precipitation is a critical issue in chemical flooding for improved oil recovery. Adsorption and precipitation profiles also play a governing role in determining the mineral wettability and sweep efficiency. The mechanisms that control both the extent of adsorption and the nature of the nanostructure of the adsorbed layer on relevant minerals were investigated in this work using mixtures of a series of surfactants of different charge and structure (nonionic alkyl ethoxylates, environmentally benign dodecyl-â-D-maltoside (DM), anionic sodium dodecyl sulfonate and cationic single chain and Gemini amines) under various conditions of pH, salinity and, most importantly, mixing ratio of the surfactants. To obtain information on rock surface, hydrophobicity of alumina particles was monitored along with the charge of the particles and interfacial tension. It was revealed that optimum conditions for low chemical loss and high oil-sweep efficiency by using mixtures with one surfactant as an active adsorbate and the other as passive (only coadsorbing with the passive one). It is proposed that the active species act as “anchors” for passive molecules to adsorb due to hydrophobic chain-chain interaction but with the hydrophilic head groups oriented toward the bulk solution, making the mineral water wetted. On the basis of these results, it is proposed that active/ passive systems with a low fraction of active component be chosen to minimize adsorption and maximize the performance of surfactants in chemical flooding.
AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana