The Potential for MEOR from Carbonate Reservoirs: Literature Review and Recent Research

Abstract

The potential for MEOR in carbonate petroleum reservoirs was assessed in a review of the relevant literature and further examined in the laboratory. This review showed that MEOR appeared to be applicable in about 40% of the carbonate reservoirs surveyed. Microbial acid, gas, and surfactant production are likely to be the more important mechanisms for MEOR from carbonates. A study of the microbiology of native produced fluids showed that a carbonate reservoir may contain a diverse microbial community; however, the number and activity of microorganisms present would probably be low, due to limiting nitrogen and phosphorous. Microorganisms could change the hydrogeologic properties of carbonate rock. The growth of an acid-producing strain through a carbonate rock core increased the permeability from <0.1 to 4.7 mD and the porosity from 11 to 16%. Laboratory study of MEOR from waterflooded limestone-packed cores showed that >40% of the remaining oil-in-place was recovered after three treatments with an acid-producing or a surfactant-producing microorganism, showing that both of these processes can increase oil recovery from carbonates. While further laboratory research is required, there is enough information to support controlled field trials of MEOR from carbonate reservoirs.