Morgantown, W.Va. — A new generation of high-performance surfactants has proven successful in mobilizing residual oil in two mature fields in Oklahoma through a project supported by the U.S. Department of Energy’s National Energy Technology Laboratory (NETL).
The University of Oklahoma, in partnership with a small independent producer, demonstrated the use of a novel surfactant formulation on two high-water-cut stripper wells—wells that produce less than 10 barrels of oil per day and produce significantly more water than oil—located in the Bartlesville formation in northeast Oklahoma. The Bartlesville formation, which to date has produced more than a billion barrels of oil, was targeted because it has thousands of active wells and hundreds of active water floods.
The investigators completed two single-well tests in the fall of 2011. The first step in each was a tracer test to measure the amount of existing residual oil—oil that remains in the ground after the easy-to-produce oil has been recovered. The next step was a chemical flood using three different surfactants combined with a polymer at 2,000 parts per million. Surfactant and polymer were mixed with reservoir brine, rather than fresh water, to reduce costs and minimize risk to the environment. Following the injection of additional brine to help the chemicals flood the reservoir, another tracer test was performed on each well to measure any change in residual oil due to the chemical flood.
In the first well, a chemical flood with a total surfactant concentration of 0.5 percent mobilized 75 percent of the residual crude oil. In the second well, with the total surfactant concentration of the chemical flood lowered to 0.23 percent, approximately 80 percent of the residual crude oil was mobilized. Subsequent laboratory experiments showed that surfactant concentrations could be reduced to 0.11 percent and still effectively mobilize crude oil, which could further reduce costs and improve environmental performance. Investigations also indicated that polymer costs may be reduced by up to 50 percent by mixing various polymers.
Based on these results, two pilot projects in Northeast Oklahoma are being designed for implementation in the fall 2012, after the NETL-sponsored project ends. It is estimated that widespread application of these techniques could result in economic production of an additional billion barrels of oil from the Bartlesville formation.