Oil Reservoir & Environmental Technologies
Bioreactor Design and Demonstration for Microbial Oxidation of Sulfides
The presence of sulfides in reservoirs and produced fluids is a function of microbial, electrochemical, and geochemical processes. Problems presented by sulfides include environmental compliance, toxicity, corrosion, reduced well performance, offensive odor, reduced monetary value of products, and increased operating costs. Technologies for removing and controlling sulfides include the use of biocides, scavenging agents, corrosion inhibitors, Claus reactors, amine plants, etc. Problems with these technologies include ineffectiveness, use of toxic chemicals, cost, and generation of toxic wastes requiring disposal.
To overcome some of these problems, biocontrol strategies (generally termed biocatalysis) are being developed that rely on bacteria that oxidize sulfides in the presence of oxygen or nitrates to produce elemental sulfur or sulfate. These bacteria can out-compete sulfate-reducing bacteria (SRB) for nutrients needed for generating sulfides, thereby further controlling sulfide production. These biocatalytic processes are less costly and more acceptable since they use inexpensive, nonhazardous chemicals and generate low-toxicity products. The goal of this project is to develop and demonstrate biocatalysis of sulfides in discrete bioreactor elements. Specific objectives are to optimize the growth and sulfide scavenging capacity of a proven nitrate-reducing, sulfide oxidizing consortium of microorganisms and develop bioreactors for field-scale design and technology demonstrations. A field trial for the process on a gas well is scheduled for summer 2001.