Engineering Rhamnolipid Biosurfactants as Agents for Microbial Enhanced Oil Recovery

Venue: 2007 SPE International Oilfield Chemistry Symposium, The Woodlands, TX, Feb. 28-Mar. 2, 2007 (http://www.spe.org/spe/jsp/meetingsearch [external site]).

Authors: Xiangdong Fang, Xi Cai Liu, Patrick J. Shuler, Yongchun Tang, and William A. Goddard III, California Institute of Technology; Qinhong Wang and Baojun Bai, University of Missouri-Rolla.

Abstract: This investigation considered engineered rhamnolipid biosurfactants as microbial enhanced oil recovery (MEOR) agents that potentially could be manufactured at low cost from renewable resources and have lower toxicity than synthetic EOR surfactants. This particular biosurfactant comes mainly from the microbe Pseudomonas aeruginosa. One disadvantage of working with this strain is that the chemical structures of the produced rhamnolipids are not easily controlled. In addition, there is a preference to use instead a completely non-pathogenic microbe. Towards that end, the researchers implanted pieces of the genetic information from a P. aeruginosa strain into E. coli to manipulate systematically the structure of the created rhamnolipids and evaluate their EOR performance by themselves (no cosurfactant or viscosity chemical added). Six E.coli strains (ETRA, ETRAB, ERAC, ETRABC, ETRhl, and ETRhl-RC) that carry different combinations of the genes involved in rhamnolipid bio-synthesis were successfully engineered and tested for their rhamnolipid production. Sand-pack coreflooding tests were run to evaluate and compare the effectiveness of these products as EOR agents. The brine with optimized pH and salt concentration in which a given biosurfactant product has its lowest interfacial tension (IFT) was used to saturate the core, perform a waterflood, and prepare the surfactant solution. Injection of 6 PV of only a 200 ppm rhamnolipid biosurfactant solution and 4 PV of a brine chaser could recover as much as half of the waterflood residual hydrocarbon (n-octane). The engineered E. coli strains that include more of the implanted genetic code had the better performance in these oil displacement tests. The IFT, biosurfactant concentration, and pH of effluents from coreflooding were monitored to address EOR mechanisms and quantify the adsorption of each product in the sand pack.

Related NETL Project: The goals of the related NETL project, “Bio-Engineering High-Performance Microbial Strains for MEOR by Directed-Protein-Evolution Technology” (DE-FC26-04BC15525), are to 1) apply advanced bio-engineering methods—such as genetic manipulation—to induce bacteria that are natural biosurfactants to perform as such at a much higher, commercially useful rate; and 2) implant the genetic information for rapid biosurfactant production into microbes adaptable to an oil reservoir environment. The performer is California Institute of Technology at Pasadena, CA.

NETL Project Contacts
NETL - Virginia Weyland (virginia.weyland@netl.doe.gov or 918 699-2041)
Cal Tech - William Goddard (wag@wag.caltech.edu or 626-395-2731)
Cal Tech - Xiangdong Fang (xdfang@peer.caltech.edu or 626-858-5077)