Chemical and Microbial Characterization of North Slope Viscous Oils to Assess Viscosity Reduction and Enhanced Recovery

• Main Authors: Patil, Shirish, Dandekar, Abhijit, Leigh, Mary Beth
• Other Authors: United States. Department of Energy.
• Format: Report
• Language: English
• Published: University of Alaska 2008
• Subjects: Alaskan North Slope; 02 Petroleum; Microorganisms; Genetics; Testing; Chemical Composition; Petroleum; Bacillus Licheniformis; Enhanced Recovery; Surface Tension; Strains; Oil Fields; Surfactants; Viscosity; Bacteria; Oil Spills; Communities; Milne Point; Alaska North Slope; north slope; Alaska
• Online Access: https://doi.org/10.2172/963366; https://digital.library.unt.edu/ark:/67531/metadc933863/

A large proportion of Alaska North Slope (ANS) oil exists in the form of viscous deposits, which cannot be produced entirely using conventional methods. Microbially enhanced oil recovery (MEOR) is a promising approach for improving oil recovery for viscous deposits. MEOR can be achieved using either ex situ approaches such as flooding with microbial biosurfactants or injection of exogenous surfactant-producing microbes into the reservoir, or by in situ approaches such as biostimulation of indigenous surfactant-producing microbes in the oil. Experimental work was performed to analyze the potential application of MEOR to the ANS oil fields through both ex situ and in situ approaches. A microbial formulation containing a known biosurfactant-producing strain of Bacillus licheniformis was developed in order to simulate MEOR. Coreflooding experiments were performed to simulate MEOR and quantify the incremental oil recovery. Properties like viscosity, density, and chemical composition of oil were monitored to propose a mechanism for oil recovery. The microbial formulation significantly increased incremental oil recovery, and molecular biological analyses indicated that the strain survived during the shut-in period. The indigenous microflora of ANS heavy oils was investigated to characterize the microbial communities and test for surfactant producers that are potentially useful for biostimulation. Bacteria that reduce the surface tension of aqueous media were isolated from one of the five ANS oils (Milne Point) and from rock oiled by the Exxon Valdez oil spill (EVOS), and may prove valuable for ex situ MEOR strategies. The total bacterial community composition of the six different oils was evaluated using molecular genetic tools, which revealed that each oil tested possessed a unique fingerprint indicating a diverse bacterial community and varied assemblages. Collectively we have demonstrated that there is potential for in situ and ex situ MEOR of ANS oils. Future work should focus on lab and field-scale testing of ex situ MEOR using Bacillus licheniformis as well as the biosurfactant-producing strains we have newly isolated from the Milne Point reservoir and the EVOS environment.