The overall objective of this project is to understand the role of mineralogy of reservoir rocks in determining interactions of reservoir minerals and their dissolved species with externally added reagants (surfactants/polymers) and their effects on solid-liquid and liquid-liquid interfacial properties, such as adsorption, wettability, and interfacial tension. A further goal is to devise schemes to control these interactions in systems relevant to reservoir conditions. Particular emphasis will be placed on the type and nature of different minerals in oil reservoirs.

Columbia University, New York, NY

Chemical EOR can be an effective method for increasing oil recovery and reducing the amount of produced water; however, reservoir fluids are chemically complex and may react adversely to the polymers and surfactants injected into the reservoir. While the goal is to alter rock wettability and interfacial tension between oil and water, rock-fluid and fluid-fluid interactions must be understood to maximize recovery and reduce costly mistakes.

Results 
The adsorption behavior of mixed polymer/surfactant and surfactant/surfactant systems on typical reservoir minerals (quartz, alumina, calcite, dolomite, kaolinite, gypsum, pyrite, etc.) is correlated to their molecular structure, intermolecular interaction and the solution conditions such pH. Predictive models have been developed and a guideline for the use of polymer/surfactant in EOR is being developed from these models.

Benefits 
This research will improve understanding of rock-fluid interactions that will help to identify reagants and operating conditions that are optimal for improved oil recovery using surfactants and polymers. This information can be applied to improve recovery from waterflooded reservoirs.

Summary 
The scope of work for this project includes:

• Study of the interactions among typical reservoir minerals (quartz, alumina, calcite, dolomite, kaolinite, gypsum, pyrite, etc.) and surfactants/polymers in terms of adsorption properties that include both macroscopic (adsorption density, wettability) and microscopic (orientation/conformation of the adsorbed layers), as well as precipitation/abstraction characteristics.
• Investigation of the role of dissolved species, especially multivalent ions, on interactions between reservoir minerals and surfactants/polymers leading to surfactant precipitation or activated adsorption. Presence of multivalent ions such as calcium, magnesium, and iron from minerals such as limestone, gypsum, and pyrite can cause catastrophic loss of reagents.
• Exploration of these interactions under simulated oil reservoir conditions. Adsorption/precipitation of surfactants under relevant conditions such as temperature, salinity, and presence of oil or emulsion are studied.
• Development of predictive models that include minerals, surfactants/polymers, and reservoir conditions such as temperature and salinity. A guideline for the use of surfactants/polymers in enhanced oil recovery is to be developed.

Mineral characterizations—SEM, BET, size, surface charge, and point zero charge—have been completed. Solution behavior tests—surface tension, interaction, ultrafiltration, and other tests—have been completed. Surfactant-mineral interactions relative to adsorption, wettability, and electrophoresis have been tested and completed. Work continues on adsorption of surfactant/polymer mixtures.

Work on the effects of multivalent ions on adsorption is approximately 50 percent complete. Investigation of variables leading to precipitation reduction—pH, temp, salinity, mixing ratio—is partially completed, as are potential optimal formulations. Modeling of the mechanisms of adsorption, precipitation, and surfactant/polymer/mineral interactions is about 80 percent complete. A guidebook for surfactant/polymer formulations is still to be developed.

(December 2008) 
This project is completed and the final report is listed below under "Additional Information".

Funding 
This project was selected in response to DOE solicitation DE- PS26-01NT41613.

$799,605 

$199,901 (20 percent of total)

NETL - Chandra Nautiyal (chandra.nautiyal@netl.doe.gov or 918-699-2021)
Columbia U. - P. Somasundaran (ps24@columbia.edu or 212-854-2926)

Final Project Report [PDF]

Publications 
Shaohua Lu, Yu Bian, Lei Zhang and P. Somasundaran, “pH dependence of adsorption of n-dodecyl-ß-D-maltoside on solids”, Journal of colloid and interface science, 316 (2007) 310–316

Qiong Zhou and P. Somasundaran, “Synergistic Adsorption of Cationic Gemini and Sugar-Based Nonionic Surfactant Mixtures on Silica”, submitted to Langmuir.

Shaohua Lu and P. Somasundaran, “Tunable synergism/antagonism in mixed nonionic/anionic surfactant layers at solid/liquid interface”, Langmuir, in press

Shaohua Lu and P. Somasundaran, Characterization of nanostructures of mixed surfactant aggregation using Analytical Ultracentrifugation. The 81st ACS Colloid & Surface Science Symposium (June 24-27, 2007).

Shaohua Lu and P.Somasundaran, Synergy among Surfactants in Solution and on Particles in Suspensions. The 81st ACS Colloid & Surface Science Symposium (June 24-27, 2007).

Lu, S. and P. Somasundaran, “Solution Behavior of Nonionic/Anionic Surfactant Mixtures,” presentation, 16th International Symposium on Surfactants in Solution, South Korea, June 2006.

Lu, S. and P. Somasundaran, “Rock Wettability Control and Chemical Loss Reduction,” proceedings, AAPG Rocky Mountain Section Annual Meeting, Billings, MT, June 2006.

Lu, Shaohua and Somasundaran, P., “Analytical Ultracentrifuge Study of Micellization of Surfactant Mixtures,” presentation, 231st ACS National Meeting, Atlanta, GA, March 2006.

Lu, S. and P. Somasundaran, “Synergy among Surfactants in Solution and on Particles in Suspensions,” poster, industrial advisory board meeting, University of Florida, February 2006.

Lu, Shaohua, Somasundaran, P., and Zhang, R., “Prediction of the Aggregate Nanostructures of Binary Surfactant Mixtures on Hydrophilic Solids,” at the 230th American Chemical Society National Meeting, Washington, D.C., August 28-September 1, 2005.

Lu, Shaohua and Somasundaran, P., “Controllable synergistic or antagonistic adsorption of surfactant mixture on solids,” 230th American Chemical Society National Meeting, Washington, D.C., August 29, 2005.