Microbial enhanced oil recovery method
The present invention provides methods for increasing the viscosity of the drive fluid for displacing oil from a subterranean formation by the use of microorganisms selected or modified for the ability to produce cell free polymers without the formation of any significant bioplugging biofilm or capsule.
1. A method of enhancing oil recovery comprising:
(a) introducing into an oil reservoir a microorganism capable of growing in an environment of waterflood fluid;
wherein said oil reservoir comprises indigenous bioplug-forming microorganisms; and
wherein said microorganism is genetically modified to (i) be deficient in its ability to produce a flow-restricting bioplug and (ii) to produce soluble cell free biopolymers in situ within the oil reservoir; and
(b) water-flooding said reservoir with a drive fluid containing a compound toxic to said indigenous bioplug-forming microorganisms to reduce the concentration of said indigenous bioplug-forming microorganisms in the oil reservoir.
2. The method of claim 1 wherein the oil reservoir is selected from the group consisting of underground reservoirs, producing wells, non-producing wells, experimental wells, exploratory wells, oil sands and other sources of heavy oil.
3. The method of claim 1 wherein the microorganism is an archaeon or a bacterium.
4. The method of claim 1 wherein the microorganism is present in a culture of microorganisms comprising a plurality of microorganisms that are genetically modified to be deficient in their ability to produce said flow-restricting bioplug, and to produce said soluble cell free biopolymers in situ within the oil reservoir.
5. The method of claim 4 wherein said microorganism is present in a culture of microorganisms comprising a plurality of microorganisms that are able to produce surfactants.
6. The method of claim 1 wherein said microorganism is able to produce surfactants.
7. The method of claim 1 wherein said microorganism is able to utilize simple carbons selected from the group comprising glucose, sucrose, mannose, starch, glycerin, organic acids, and other simple sugars.
8. The method of claim 1 wherein said soluble cell free biopolymers comprise a polysaccharide.
9. The method of claim 1 wherein said microorganism is further characterized by (i) containing functional genes for carbohydrate metabolism and conversion of carbohydrates into high molecular weight polysaccharides; (ii) lacking functional genes for formation of a biofilm; (iii) containing functional genes for production of surfactants; and (iv) being regulated to express the functional genes of steps (i) and (iii), and grow in the waterflood fluid.
10. The method of claim 1 further comprising a step of injecting a nutrient mixture into said reservoir.
11. The method of claim 1 , wherein said microorganism is further naturally deficient in its ability to produce said flow restricting bioplug.
12. The method of claim 1 , wherein said microorganism is selected for its ability to penetrate 0.2 μm filters or sandstone cores of 50 mD or less permeability.