Microbiology In the Oil Patch: A Review

Abstract With the reality of our depleting natural resources, scientists and engineers are working to maximize the potentials of existing oil fields while minimizing ecological impacts. All divisions within the oil patch are currently investigating the diverse and vast potential bacteria have for industry. Current applications include: oil and gas exploration microbial enhanced secondary oil recovery techniques minimization of microbial induced corrosion and reservoir souring, bioprocessing of fossil fuels and environmental applications. This paper will discuss recent advances and reference pertinent sources. Introduction Biological systems have a significant role in the petroleum industry. An understanding of the positive and negative impacts of these systems can drive management decisions in all levels of the industry from exploration through production refining and eventual site closure and reclamation. This document provides an overview of some important impacts biotic systems are having in the oil-patch and how these systems are being harnessed or controlled. In addition several innovative applications for biological systems are reviewed. Some of the topics addressed include: microbial enhanced oil recovery (MEOR), bacterial contribution to reduced fluid injectivity, biological exploration techniques, reservoir souring, sour produced water treatments, microbial induced corrosion bioprocessing of fossil fuels, and environmental remediation and site reclamation applications. Exploration Microbial surveys have been successfully used to predict locations of oil and gas reserves (1.2). In general these techniques measure signature microbial populations which are often associated with anomalous hydrocarbon micro seepage from oil and gas reservoirs. One method used is called the Microbial Oil Survey Technique (MOST) developed by Phillips Petroleum. In this method anomalous hydrocarbon seeps are identified by observing fluctuations in microbial population and distribution within a survey area (I). Injectivity Problems In the late 50's and early 60's a great deal of literature was published on wellbore plugging as a result of bacterial growth. Bacteria produce high molecular weight polysaccharide polymers which are deposited by biofilms growing on the surface of a formation. This polymer deposition can cause a tremendous reduction in well injectivity. Several earl' publications link biofilm growth to reduced fluid iniectivity of wells (3.4.5). Out of this de"e1oped the popular but impractical theory that reservoirs should be formaldehyde flushed to kill the bacteria particularly the Sulfate Reducing Bacteria (SRB). Microbial Enhanced Oil Recovery There are four primary processes that contribute to Microbial Enhanced Oil Recovery (MEOR): 1) Production of Gases- These gases include CO2. H2, . N2 and CH4 Microorganisms down-hole produce these gases as a result of their natural metabolic processes. These gases can enhance oil recovery by increasing the wells internal pressure and decreasing the viscosity of crude oil due to solubility effects (6.7). 2) Organic Acid Production- Low molecular weight fatty acids are one of the byproduct of microbial metabolism. These compounds have application to MEOR b' their capabilities to increase rock dissolution and enhance permeability (predominantly in carbonate formations) (6). 3) Biosurfactant Production- Surfactants are often extracellular organic molecules produced by bacteria.