The program supported the development, engineering, and application of biotechnology for exploration and production of petroleum as well as for the mitigation of field conditions detrimental to the environment. The purpose of the program was to research more cost-effective and environmentally acceptable methods of microbial enhanced oil recovery (MEOR). This research involved elucidation and quantification of microbial mechanisms responsible for oil displacement. The project also sought to develop MEOR systems and to apply them in field demonstrations whose cost was shared with industry.

Program
The Idaho National Laboratory (INL) Biotechnology for Oilfield Operations program (DPR5AC312) was funded under the National Laboratory Partnership Program as a Field Work Proposal at the discretion of the Office of Fossil Energy.

Idaho National Laboratory
Idaho Falls, ID

New Mexico Tech Petroleum Recovery Research Center
Socorro, NM

University of Wyoming
Laramie, WY

ConocoPhillips
Bartlesville, OK

Chevron Petroleum Technology Company
La Habra, CA.

MEOR processes historically have been recognized as offering the potential for being more cost-effective and environmentally friendly than existing chemical EOR processes. The original objectives of this research program were to determine the mechanisms of oil recovery by microbial systems in terms of variables such as interfacial tension, fluid viscosities, wettability alteration, and adsorption that are well-known in EOR technology to control recovery effectiveness. There is a widespread interest in MEOR processes in the oil industry as well as continuing skepticism because of the lack of information, identification, and quantification of the controlling mechanisms. Independent operators have a significant interest in MEOR because of its promise of less capital-intensive but more cost-effective processes and as a potential process for remediation of reservoir souring.

Biosurfactants-surface-active molecules produced by microorganisms-have numerous desirable properties for application as EOR agents, including a fairly broad range of pH and salt tolerance, low toxicity profiles, and potentially low production cost. The use of biosurfactants, as with many other biological products, is limited due to high costs associated with the media required to grow the microorganisms and to separate the product from the spent culture.

Project Results
INL successfully produced surfactin from potato-process effluents for possible use as an economical alternative to chemical surfactants for improving oil recovery. INL research demonstrated the feasibility of producing surfactin in cultures of Bacillus subtilis grown on soluble starch as well as the utility of applying biosurfactants to EOR. The project also demonstrated the ability to produce surfactin from agricultural-process effluents, described the impact of effluent pretreatment, and evaluated the application of novel reactor configurations for production and separation from actual process effluents.

Benefits
The project demonstrated progress toward developing an alternate technology for modifying permeability, thus extending the life of a reservoir and preventing premature abandonment. The program supported the development, engineering, and application of biological systems for EOR, environmental remediation, improved processing for utilization of natural resources, creation of new markets for existing commodities, and advanced industrial processes with lessened environmental impact and increased energy efficiency. Further, the program was consistent with the US DOE mission to "promote activities and policies through its oil technology and natural gas supply programs to enhance the efficiency and environmental quality of domestic oil and natural gas exploration, recovery, processing, transport, and storage." Additionally, this project directly supported the focus areas of Reservoir Life Extension; Advanced Drilling, Completion, and Stimulation Systems; Effective Environmental Protection; and Cross-Cutting Areas.

Project Summary
The project:

• In early stages documented the applicability of microbial surfactants that either were generated in situ or applied after ex situ generation and that microbial surfactants (specifically those produced by Bacillus licheniformis) were not inactivated by reservoir conditions or oil composition.
• Developed instrumentation to evaluate interfacial tensions by video image analysis of inverted pendant drops to measure the changes caused by microbial surfactants.
• Undertook research to evaluate wettability with the New Mexico Petroleum Recovery Research Center (NMPRRC) and the University of Wyoming, which led to the documentation of brine composition as a key element in oil recovery.
• Investigated several flow conformance entities, including large molecular weight (dextran), small molecular weight (cyclodextrin), and reservoir-reactive (curdlan).
• Evaluated the production and gelling characteristics of dextran produced naturally from Leucononstoc mesenteroides using fishmeal and fish solubles as a nutrient source. Determined that phosphate promotes gelling of dextran.
• Investigated the production and application of reactive microbial polymers from Agrobacterium sp. Determined that curdlan, a soluble biopolymer, interacted with Berea sandstone to cause a decrease in pH leading to gel formation and a reduction in permeability.
• Characterized surfactants produced by Bacillus subtilis for brine compatibility and application in reservoir environments.
• Compared the EOR potential of surfactants produced by Bacillus licheniformis and Bacillus subtilis.

Early work demonstrated that surfactin could be produced from an inexpensive low-solids potato process effluent with minimal amendments or pretreatments. Research also established that surfactin could be produced by Bacillus subtilis ATCC 21332 cultures and recovered by foam fractionation in an airlift reactor. Results using both purified potato starch and unamended low-solids potato process effluent as substrates for surfactin production indicated that the process was oxygen-limited and that recalcitrant indigenous bacteria in the process effluent hampered continuous surfactin production. This limitation was addressed by use of a chemostat reactor operated in batch mode for producing surfactin with concomitant use of an antifoam to prevent surfactant loss. The antifoam did not interfere with the surfactin's recovery (by acid precipitation) or its efficacy. Surfactants enhance the recovery of oil through reduction of the interfacial tension between the oil and water interfaces or by effecting changes in the wettability index of the system. Experimental variables included sodium chloride (0 to 10%, w/v), pH (3 to 10), and temperature (21 to 70°C). Each of these parameters-and selected combinations-resulted in discreet changes of surfactin activity.

Polymer injection has been used in reservoirs to alleviate contrasting permeability zones. Current technology relies on cross-linking agents to initiate gelation. Use of biological polymers is valuable because they can block high-permeability zones, are environmentally friendly, and have potential to form reversible gels without the use of cross-linkers. The production of a reactive alkaline soluble biopolymer from Agrobacterium sp. ATCC 31749, which gels upon decreasing the pH of the polymer solution, was evaluated. The focus of the study was to determine the impact of an alkaline-soluble biopolymer on permeability. Permeability modification was investigated by injecting the alkaline biopolymer into Berea sandstone cores and defining the contribution of pH, salt, temperature, and crude oil on gelation. The biopolymer was soluble at a pH above 11 and gelled at pH below 10.8. The interaction of the soluble biopolymer with the geochemistry of a Berea sandstone core decreased the pH sufficiently to form a gel, which subsequently decreased permeability. Effluent pH of control cores injected with 0.01M KOH (pH 12.0) and 0.1M KOH (pH 13.0) decreased to 10.6 and 12.7, respectively. Despite the reduction of pH in the control cores, permeability increased. In contrast, when biopolymer was injected, the buffering capacity of the core caused the biopolymer to form a gel and subsequently reduce permeability. Permeability of the sandstone core injected with biopolymer decreased greater than 95% at 25°C in the presence of 2% NaCl, and crude oil; however, permeability increased when the temperature of the core increased to 60°C. Residual resistance factors of Berea cores treated with biopolymer increased 800-fold compared to cores without biopolymer. Therefore, internal sandstone core buffering of an alkaline biopolymer yielding a stable gel could potentially lead to an alternate technology for modifying permeability.

(October 2005)
Program execution enabled and initiated technical growth in other important areas in research projects at NMPRRC, University of Wyoming, University of Tulsa, Montana State University, University of Kansas, ConocoPhillips, ChevronTexaco Corp., and Halliburton.

Publications
"Surfactin Production from a Potato-Process Effluent by Bacillus subtilis in a Chemostat," Noah, K.S., Bruhn, D.F., and Bala, G.A., 2004. Pending publication: Applied Biochemistry and Biotechnology.

"Characterization of Surfactin from Bacillus subtilis for Application as an Agent for Enhanced Oil Recovery," Schaller, K.D., Fox, S.L., Bruhn, D F., Noah, K.S., and Bala, G.A. Applied Biochemistry and Biotechnology, pp. 827-836, Vol. 113-116, 2004.

"Permeability Modification Using a Reactive Alkaline-Soluble Biopolymer," Fox, S. L., Xie, X., and Bala, G.A., Paper 592b, 2004 AIChE Annual Meeting.

"Microbiological Production of Surfactant From Agricultural Process Residuals for IOR Application," Bala, G.A., Fox, S.L., and Thompson, D.N., SPE Paper 75239, Proceedings of the 13th Annual DOE/SPE Symposium on Improved Oil Recovery, 2002.

"Development of Continuous Surfactin Production from Potato-Process Effluent by Bacillus subtilis in an Airlift Reactor," Noah, K.S., Fox, S.L., Bruhn, D.F., Thompson, D.N., and Bala, G.A. Applied Biochemistry and Biotechnology, pp. 803-813, Vols. 98-100, 2002.

$4,372,000 (including subcontracts to universities)

$1,359,000 (24% of total)

NETL - Sue Mehlhoff (sue.mehlhoff@netl.doe.gov or 918-699-2044)
INL - Gregory A. Bala (gregory.bala@inl.govor 208-526-8178)