Evaluation of Commercial, Microbial-Based Products to Treat Paraffin Deposition in Tank Bottoms and Oil Production Equipment

Period Covered by Report: June 1, 2003 through September 30, 2003
EPA Agreement Number: R 827015-01-0
Title: Evaluation of Commercial, Microbial-Based Products to Treat Paraffin
Deposition in Tank Bottoms and Oil Production Equipment
Investigators: L. M. Gieg, M. J. McInerney, and J. M. Suflita
Institution: University of Oklahoma
EPA Project Officer: Bala Krishnan
Project Period: June 1, 2002 through May 31, 2004
Project Amount: $150, 000 + cost extension
Research Category: Well-Bore Cleanout

Keywords:

Petroleum, bioremediation, microbiology

Objective:

We aimed to determine the mechanism(s) of action of commercially available, microbial formulations used to treat paraffin deposition in the oil field. Because there are many conflicting reports by producers on the efficacy of microbial treatments to remedy paraffin deposits, it is not known why microbial treatments work under some conditions but not others. Knowledge of the mechanism(s) used by microorganisms to remediate paraffin deposits is a critical first step to understanding how the application of microbial treatments for paraffin removal can be optimized in the oil field. The results of this study will benefit the domestic oil industry because understanding the mechanisms of action of these products will allow the independent producer to determine the conditions under which they are likely to succeed and to determine if and when the purchase of commercial microbial paraffin treatments represents a wise expenditure of investment dollars. <>

Progress Report/Accomplishments:

As summarized in the previous Annual Report, we have completed the preliminary screening experiments for two crude oils (Alaska Oils A & B) selected by ConocoPhillips for this research project. Using the wax appearance temperature (WAT) test, which uses cross- polarized microscopy in order to measure the temperature at which paraffin crystals begin to form when a given oil is cooled under controlled conditions, we found that the addition of a commercial microbial formulation to Alaska Oil A did not have any substantial reduction in the WAT relative to microbe-free controls under a variety of conditions. In contrast, we did observe a statistically significant difference in the WAT value of Alaska Oil B incubated at 60°C under aerobic conditions relative to controls. We calculated a 7.2% reduction in the WAT value relative to controls. For the purposes of this research, microbial paraffin treatments that lowered the WAT by a minimum of 5% over that of the parallel microbial- free controls were considered successful for the preliminary screening assays. A lowering of the WAT values suggested that troublesome long-chain hydrocarbons have been "treated" by the microbial formulations. These positive results observed at 60°C with Alaska Oil B led us to establish Stage II experiments in order to pinpoint the mechanism of action of the microbial formulation which caused the significant reduction in the WAT values of this oil.

Thus, during this reporting period, detailed mechanism experiments were established with Alaska Oil B incubated at 60°C. Incubations were set up under 6 different conditions with the following amendments: (1) whole formulation; (2) cells only; (3) supernatant only; (4) whole formulation plus chloramphenicol; (5) heat-killed whole formulation; and (6) no microbes added (sterile control). All incubations were done in triplicate under both aerobic and anaerobic conditions. Surface tension measurements and emulsification assays were performed at time 0 and after 35 and 62 days of incubation to determine whether added microbial cells were treating paraffin by producing either biosurfactants or bioemulsifiers. Even after 62 days, surface tension measurements made on microbe-amended incubations did not differ significantly from microbe-unamended controls (e.g. sterile controls, and those incubations only receiving culture supernatant). Further, very little emulsifying activity was observed. These results suggested that biosurfactant nor bioemulfisifier production is a predominant mechanism occurring during paraffin treatment of Alaska Oil B at 60°C under aerobic or anaerobic conditions. Work is ongoing to examine oil profiles and analyze culture supernatants to determine whether paraffin biodegradation is occurring in these incubations.