Oil & Natural Gas Projects
Exploration and Production Technologies
Dilute Surfactant Methods for Carbonate Formations
This project was selected in response to DOE's Oil Exploration and Production
solicitation DE-PS26-01NT41048 (July 2001).
The goal of this research is to evaluate dilute (hence relatively inexpensive)
surfactant methods for carbonate formations and identify conditions under which
they can be effective.
University of Houston
Surfactants have been identified that alter wettability of calcite minerals
aged with a crude oil and that lower interfacial tension. Surfactant adsorption
can be minimized by the use of an alkali. Laboratory imbibition tests show about
61% oil recovery with an anionic surfactant and 37% in the case of a cationic
surfactant. A numerical model has been developed that fits the rate of imbibition
of the laboratory experiments. Field-scale fracture-block simulation shows that
as the fracture spacing increases, so does the time of recovery.
The waterflood recovery in fractured carbonate reservoirs is typically very
low. This dilute surfactant method can be used to improve the oil recovery in
high-permeability reservoirs by almost 60%.
There are many carbonate reservoirs in the United States (and the world) with
light oil and fracture pressure below its minimum miscibility pressure (or the
reservoir may be naturally fractured). Many carbonate reservoirs are naturally
fractured. Waterflooding is effective in fractured reservoirs, if the formation
is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet, and
recoveries with conventional methods are low (less than 10%). Thermal and miscible
tertiary recovery techniques are not effective in these reservoirs. Surfactant
flooding is the only hope, yet it was developed for sandstone reservoirs in
the past. This project is aimed at developing an inexpensive, surfactant-based
process for improved oil recovery.
The major achievements of this project are:
- Identification of anionic surfactants that alter wettability and reduce surface
- Reduction of adsorption by the use of an alkali.
- Laboratory demonstration of high oil recovery by surfactant solution imbibition.
- Mechanistic simulation showing the scale-up of the process.
This project is aimed at developing a dilute surfactant flooding process
for fractured carbonates. Researchers have conducted laboratory tests with
a West Texas crude oil. They have matched the experiments with mechanistic
simulations. More than 60% of the oil can be recovered by spontaneous imbibition
of a 0.05 percent by weight surfactant solution.
Current Status (August 2005)
The five tasks for the project are 1) adsorption, 2) wettability alteration,
3) gravity and viscous mobilization, 4) imbibition, and 5) simulation. Researchers
have finished the first three tasks and are currently working on the last
two tasks, which will be completed in the next four months.
Seethepalli, A., Adibhatla, B. and Mohanty, K.K., Physicochemical Interactions
During Surfactant Flooding of Carbonate Reservoirs, SPE J., 9 (4), 411-418,
Kumar, K., Dao, E., and Mohanty, K.K.,Atomic Force Microscopy Study of Wettability
Alteration, SPE 93009, Proceedings of SPE Intl. Symp. on Oil Field Chemistry,
Woodlands, Feb. 2-5, 2005.
Project Start: June 24, 2002
Project End: November 23, 2005
Anticipated DOE Contribution: $592,661
Performer Contribution: $150,000 (20% of total)
NETL - Betty Felber (firstname.lastname@example.org or 918-699-2031)
U. of Houston - K.K. Mohanty (email@example.com or 713-743-4331)
Spontaneous imbibition with different surfactant brines (about 58% OOIP).
The sample on the far right has no imbibition because of the absence of surfactants.