Investigations of mechanisms of microbial enhanced oil recovery by microbes and their metabolic products

Abstract

Experiments at NIPER have demonstrated that oil mobilization by microbial formulations is not merely the result of the effects of the metabolic products from the in situ fermentation of nutrient. A combination of two microorganisms, Bacillus licheniformis, NIPER and a Clostridium species (NIPER 6) was determined to be an effective microbial formulation for the recovery of residual crude oil in porous media. Flask tests with various nutrients and environmental conditions were used to evaluate the growth and metabolite production of NIPER 1 and 6. Several interfacial tension (IFT) measurements were conducted using certain metabolic products from the combined microbial cultures NIPER 1 and NIPER 6. Nonane was used as the oil for these experiments, since crude oil from Delaware-Childers field emulsifies very easily. The IFT of a selected microbial formulation were measured with two different crude oils using brines of varying salinities. Comparisons were made with saline brines containing only the nutrient and with microbial metabolite solutions from which the active cells have been removed by filtration to isolate the specific effects of the microbial cells. Etched-glass micromodel studies showed that the microbial formulation effectively mobilized crude oil trapped after waterflooding. Wettability alteration and unsteady-state relative permeability tests were performed in Berea Sandstone cores. 16 refs., 17 figs., 12 tabs.