Aerobic enhanced oil recovery: analysis of the mechanisms and a pilot study

Abstract

The technique that uses microorganisms to improve oil production in petroleum reservoirs is known as microbial enhanced oil recovery (MEOR). Aerobic microbial enhanced oil recovery is a method which is based on stimulating indigenous oil degrading bacteria by introducing oxygen (air) and nutrients into the injection water in an existing water flood. The primary emphasis is to promote biological growth in the oil/ water interface, which reduces the interfacial tension and mobilizes the oil. This process is proven to work in laboratory studies, and successful field tests have been reported in USSR. A pilot test on AMEOR has been initiated in the North Brock field in Oklahoma. The treatment, which consists of a continuous injection of air together with an appropriate nutrient supply, has been going on for seven months. So far no increase in oil production has been observed in the full field scale. However, well tests performed on each production well show an increase in oil production from two wells. This increase does not have any effect on the total oil production due to decline periods in the other wells. The most positive observation in the field test is an increase in the differential pressure observed right after the start of oxygen injection. This may be a result of reduced permeability to water in the oil bank, indicating an oil mobilization process in the reservoir. The same effect has also been observed in the laboratory core studies. The process is also proven to be time dependent and independent of the number of pore volumes flooded. It is concluded that it is too early in the process to experience any incremental oil production. The pressure increase may indicate that a mobilization process is going on and that it will only be a matter of time before any additional oil will be experienced in the field. This research involves an analysis of the pilot study in the North Brock field, in addition to a description of the AMEOR technique, effects and limitations. A comparison to other conventional MEOR techniques is also given.