Microbial enhanced oil recovery and compositions therefor

A method for recovering oil from an oil-bearing reservoir, said reservoir having at least one injection well and at least one production well, said method comprising the steps of:

• (a) introducing into an injection well of said reservoir substantially only (A) a microbial formulation comprising (i) a substantially pure culture of Bacillus licheniformis, strain JF-2 (ATCC #39307) and (ii) a substantially pure culture of a solvent-secreting species of microorganism from the genus Clostridium which is selected from the group consisting of ATCC #53797 and ATCC #53798, said cultures of microorganisms being injected sequentially, in an order which is reverse to the ordering according to motility;
• and (B) a nutrient composition which consists essentially of an aqueous solution of nutrients capable of supporting growth of the microorganisms of said formulation, the species of microorganisms in said formulation being capable, upon incubation after injection with a nutrient into said reservoir, of surviving in said reservoir and said formulation being capable of displacing oil present at a concentration not substantially greater than waterflood residual oil saturation, said nutrients being injected before each of said sequential injections of said cultures of microorganisms;
• (b) shutting-in said injection well for an amount of time sufficient for the species of microorganisms of said microbial formulation to acclimate to said reservoir;
• (c) after step (b) injecting a fluid into said injection well to drive said displaced oil to said production well.

A method for recovering oil from an oil-bearing reservoir by sequentially injecting substantially pure cultures of microorganisms, said reservoir having at least one injection well and at east one production well, said method comprising the steps of:

• (a) introducing into an injection well of said reservoir a substantially pure culture of Bacillus licheniformis, which species of microorganism secretes a surfactant;
• (b) introducing into an injection well of said reservoir a substantially pure culture of a species of microorganism from the genus Clostridium, which species secretes a solvent selected from the group consisting of alcohols, ketones and acids, said cultures being injected sequentially in a predetermined order;
• (c) introducing into said injection well a nutrient composition which consists essentially of an aqueous solution of nutrients capable of supporting growth of the microorganisms, a species of said sequentially injected microorganisms being capable, upon incubation after injection with a nutrient into said reservoir, of surviving in said reservoir and said sequentially injected microorganisms being capable of displacing oil at a concentration not substantially greater than water flood residual oil saturation;
• (d) shutting-in said injection well for an amount of time sufficient for said sequentially injected species of microorganisms to acclimate to said reservoir;
• and
• (e) after step (d) injecting a fluid into said injection well to drive said displaced oil to said production well.