CRUDE GLYCEROL AS SUBSTRATE FOR SULFATE-REDUCING BACTERIA FROM A MATURE OIL FIELD AND ITS POTENTIAL IMPACT ON SOURING

Abstract

Crude glycerol (CG) is an abundantly available and cheap by-product from biodiesel production. Value-added applications for CG are highly wanted by industry and several processes such as the use of CG for enhanced oil recovery have been proposed. The aim of this study was to evaluate the sulfide production of sulfate-reducing bacteria (SRB) indigenous to oil reservoirs using CG as substrate. The samples of CG were obtained from a biodiesel production plant, processing castor beans, soybeans, cotton, and waste oils and fats. Growth tests were performed in Postgate medium, with different types and concentrations of CG, and a mixed inoculum of SRB isolated from the produced water of a mature oil well of Bahia (Brazil). The experiment was monitored by measuring the concentration of sulfide using a colorimetric method. The results showed that SRB grew and produced more than 250 ppm sulfide at CG concentrations of 2%. However, at CG concentrations of 3% or higher, the biogenic production of sulfide was reduced. The study demonstrates that CG will likely stimulate SRB in oil fields, whenever CG is present at lower concentrations. Maintaining CG concentrations inhibitive to SRB will not certainly be achievable throughout oil reservoirs. Dosing CG to oil fields may lead to problems associated with souring in longer terms. The utilization of CG by SRB could in turn be interesting for other biotechnological processes, e.g. metal recovery processes based on precipitation with biologically formed sulfide.