The main objectives of our present series of study are (1) selection of useful anaerobes for MEOR, (2) estimation of bacterial growth and their metabolic activities at reservoir conditions, (3) establishment of quantitative evaluation techniques of capabilities of anaerobes in improving oil recovery, and (4) investigation of recovery mechanisms. This paper describes methods and results of sampling and screening of enrichment anaerobic microbes, as a first stage of our fundamental studies on MEOR. Consequently, we selected possibly useful anaerobes and investigated their abilities.
Samples were collected from formation waters, soils in oil fields, lakes and rivers. We obtained 22 kinds of microbes from these samples, and discovered 20 anaerobes among them through enrichment culture. The number of anaerobes selected for further experiment was 14, as a result of screening with the medium of 4% molasess with 0.8% Nutrient Broth at 30°C. Then, we investigated the effects of microscopic environment and presence of minerals on their activities. As a result, we obtained 6 useful anaerobes (3H, 4D, 6B, 7A, 8L, 9A) which had productivity of effective metabolites, though some other microbes were obstructed to grow under such conditions, which implied that both factors, inorganic salts and (porous) media, must be taken into account in screening. In addition, the microscopic observation showed that regarding some enrichment anaerobes, the kind of anaerobe having the predominant multiplication changed with media. Therefore, the isolation was carried out, and 2 isolated microbes from enrichment anaerobe 3H and 4 from 7A were obtained.
