METHOD OF MODIFICATION IN OIL RESERVOIRS USING RESIDENT MICROORGANISMS AND NUTRIENT SUPPLEMENTATION THROUGH BIOLOGICAL WETTABILITY ALTERATION

Abstract

A method for improving oil recovery includes determining a specific nutrient package or formulation for stimulating and altering resident microorganisms to increase wettability of reservoir rock formations in oil reservoirs. Once determined, the specific nutrient package is applied to the oil reservoir to stimulate the resident microorganisms. The stimulating application is followed by a period of nutrient limitation where the physiology and surface characteristics of the resident microorganisms are altered. Once altered, the resident microorganisms interact with the reservoir rock formations to change the adhesion tension of the reservoir rock formation to a more water wet condition so that oil will flow more freely rather than be bound to the rock surface.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/33 6,353 filed Jun. 18, 2013

BACKGROUND OF THE INVENTION

This invention relates to the process of using resident microorganisms to change the wettability of oil field reservoirs. More particularly this invention contemplates a mechanism for recovering otherwise unrecoverable oil using a method of manipulating resident microorganisms in a reservoir through nutrient supplementation and then nutrient limitation to induce physical and metabolic changes that lead to an increase in oil recovery by changing the wettability in the impacted portions of the reservoir to a more water-wet condition.

SUMMARY OF THE INVENTION

A method for improving oil recovery includes determining a specific nutrient package or formulation for stimulating and altering resident microorganisms to change wettability of reservoir rock formations in oil reservoirs. Once determined, the specific nutrient package is applied to the oil reservoir to stimulate the resident microorganisms. The stimulating application is followed by a limiting period where the physiology and surface characteristics of the resident microorganisms are altered. Once altered, the resident microorganisms interact with the reservoir rock formations to change the adhesion tension of the reservoir rock formation to a more water wet condition so that oil will flow more freely rather than continue being hound to the rock surface.

BRIEF DESCRIPTION OF THE FIGURE

The FIGURE is a flow diagram of a method of enhancing oil recovery.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method is disclosed to increase oil recovery from oil reservoirs of all types including, but not limited to, sandstone, carbonate, conglomerate, shale, siltstone or other rock-type exhibiting oil-wet or mixed wettability characteristics. The method contemplates the recovery of oil from subsurface oil reservoir by modifying the characteristics of resident microorganisms found in the oil reservoir.

The method includes the application of a specific nutrient formulation to modify and/or stimulate some of the resident microorganisms to interact with oil contained In reservoir rock formations. Preferred is the application of a specific package of nutrients in a liquid form that can be diluted to produce a range of concentrations from 100 grams per liter to 0.0001 grams per liter in the treated volume. The delivery of the nutrient formulation occurs via water injection wells or producing wells. In one embodiment the nutrient is a digest or extract of protein and/or an organic cell extract of prokaryotic or eukaryotic ceils. In one form, the nutrient formulation stimulates desirable resident microorganisms and suppresses some undesirable resident microorganisms.

Specific nutrient formulations facilitate microbe-mediated oil release in reservoirs over a wide range of temperature and salinity that are compatible with biological life. In one embodiment, the invention contemplates use of a series of analyses that lead to formulation of a specific nutrient package to perform a microbiological response analysis under actual reservoir conditions of the resident population of microorganisms with the intent of refining the treatment of a reservoir to optimize changes in the resident microorganisms to take advantage of hydrophobic properties that induce the recovery of oil though altered wettability.

The step of stimulation of targeted resident microorganisms is followed by specific nutrient limitation that alters the physiology and surface characteristics of the targeted microorganisms. This cycle of nutrient supplementation and depletion may be repeated. In one embodiment this modification of the resident microorganisms includes changes in cell size or hydrophobic properties of reservoir fluids that alter surface-active properties. Typical reductions in the microorganism cell volume is 50% or more, The steps of stimulation and modification of the oil interactive properties of the resident microorganisms is to a level, which enhances oil recovery. The surface active properties are such that associated wettability is changed such that adhesion tension is changed so the water more readily spreads and adheres to the reservoir rock surfaces. In one embodiment a genetic analysis of resident microorganisms in produced water is included in the method to aid in the determination of the presence of the oil interactive microorganisms with the capacity to alter wettability.

DEFINITIONS

“Wettability” is described as the adhesion tension. It is a function of the interfacial tension and determines which fluid (oil or water) will preferentially wet (adhere to) the solid surface of the reservoir rock. If the adhesion tension is large, the denser phase liquid will readily spread out and tend to coat the surface of the reservoir rock. If the adhesion tension is small, the denser fluid will only be weakly attracted to the surface. By changing the reactive character to a more water wet condition, oil will flow more freely rather than being bound to the rock surface. (Amyx, Bass and Whiting, Petroleum Engineering Principles, McGraw-Hill, 1960)

“Resident Microorganisms” are defined as microorganisms that occur in oil reservoirs, prior to the envisioned treatment, irrespective of the microorganism's origin or where they occur within the oil-bearing strata.

Claims

1. A method of improving oil recovery, comprising the steps of:

applying a specific nutrient formulation to stimulate resident microorganisms in oil reservoir rock formations;

limiting availability of the specific nutrient formulation to alter the physiology and surface characteristics of the resident microorganisms; and

allowing the altered microorganisms to interact with the reservoir rock formations to change adhesion tension of the reservoir rock formations to a more water wet condition to allow oil to flow more freely.

2. The method of claim 1 further comprising the step of conducting a series of analyses to determine the contents of the specific nutrient package.

3. The method of claim 1 wherein surface-active properties of the resident microorganisms are modified.

4. The method of claim 1 wherein cell volume of the resident microorganisms are reduced by fifty percent or more.

5. The method of claim 3 wherein interfacial tension and relative permeability of the surface-active properties are changed.

6. The method of claim 1 wherein the specific nutrient package is in liquid form and diluted in a treated volume in a concentration range between 100 grams per liter and 0.0001 grams per liter.

7. The method of claim 1 wherein the specific nutrient formulation facilitates a microbe-mediated oil release in reservoirs up to 130 c and 150,000 ppm total dissolved solids.

8. The method of claim 1 wherein the specific nutrient formulation stimulates desirable resident microorganisms and suppress undesirable resident microorganisms.

9. The method of claim 1 wherein the delivery of the specific nutrient formulation is selected from a group consisting of water injection wells, producing wells, and disposal wells.

10. The method of claim 1 further comprising the step of conducting genetic analysis of the resident microorganisms to determine whether oil interactive microorganisms capable of altering wettability are present.