Monday, June 28, 2010

DuPont Identifies Anaerobic Bacteria For Improved Heavy Oil Recovery

E.I. du Pont de Nemours and Company (Wilmington, DE) earned U.S. Patent U.S. Patent 7,740,063  for a method to identify novel anaerobic denitrifying bacteria utilizing petroleum components as sole carbon source

According to inventors Robert D. Fallon, Linda L Hnatow, Scott Christopher Jackson and Sharon Jo Keeler, this invention relates to the field of environmental microbiology and modification of heavy crude oil properties using microorganisms. More specifically, pure anaerobic denitrifying microorganisms are identified and applied to modify the properties of heavy crude oil to make it easier to recover the oil. 

Background

The challenge to meet the ever increasing demand for oil includes increasing crude oil recovery from heavy oil reservoirs. This challenge has resulted in expanding efforts to develop alternative cost efficient oil recovery processes. Heavy hydrocarbons in the form of petroleum deposits and oil reservoirs are distributed worldwide. These oil reserves are measured in the hundreds of billions of recoverable barrels. Because heavy crude oil has a relatively high viscosity, it is essentially immobile and cannot be easily recovered by conventional primary and secondary means.

Microbial Enhanced Oil Recovery (MEOR) is a methodology for increasing oil recovery by the action of microorganisms. MEOR research and development is an ongoing effort directed to developing techniques to use microorganisms to modify crude oil properties to benefit oil recovery.

Methods for identifying microorganisms useful in MEOR processes have been described. These methods require identification of samples drawn from an oil well or reservoir comprising a consortium of microorganisms and enrichment or evolution of populations in the sample, under specific conditions with defined nutrient media

Microbial degradation of hydrocarbons has also been described, under aerobic or mixed (aerobe and anaerobic) conditions, as a mechanism for oil viscosity reduction. Degradation under these circumstances requires evolved microorganisms and particular nutrients which have not been demonstrated as an economic means for improving oil recovery.

Thus, there is a need for developing methods to: 1) identify microorganisms that could be used to enhance oil recovery under economic conditions; 2) identify microorganisms that can grow on oil under anaerobic conditions without the need for nutrient supplementation or long term enrichment of indigenous microorganisms; and 3) use said identified microorganisms, in a cost-efficient way, to improve oil recovery.

 DuPont’s Discovery

DuPont’s methods describe how to identify indigenous bacterial genera, and using phylogenetic identification techniques based on the phylogeny of the indigenous genera to select pure anaerobic bacterial cultures that respire by denitrification and that are capable of growing on oil without complex nutrient supplementation.

Further, the methods are described for using these pure cultures, without enrichment or directed evolution, to economically enhance oil recovery. These pure cultures are used to enhance oil recovery in one or more of the following ways: (1) alter the permeability of the subterranean formation to improve water sweep efficiency; (2) produce biosurfactants which decrease surface and interfacial tensions; (3) mediate changes in wettability; (4) produce polymers which facilitate mobility of petroleum; and (5) generate gases (predominantly CO2) that increase formation pressure and reduce oil viscosity.

Specifically, DuPont’s invention relates to the application of rDNA phylogenetic typing of bacteria found in environmental samples obtained from an oil well or reservoir, followed by identifying and obtaining pure cultures of known bacterial species with similar genetic makeup, then screening these strains for relevant functionalities, such as capability to grow on crude oil under denitrifying conditions. 

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