DEVELOPMENT AND FIELD EVALUATION OF A NEW MICROBIAL EOR CONCEPT

Abstract

For over 40 years it has been speculated that bacteria can facilitate, increase or extend oil production from petroleum reservoirs. This speculation was supported in the laboratory by dramatic increases in oil recovered from experimental systems and in the field by anecdotal accounts of improvements in oil production. Most of these studies were poorly conceived and inadequately controlled. This drew industry criticism and created an environment where proposals to implement microbiologically enhanced oil recovery (microbial EOR) were summarily dismissed. The program implemented for the Alton Field, Surat Basin, was designed to overcome industry scepticism and document unambiguously in the field the effectiveness of a new microbial EOR strategy called Biological Stimulation of Oil production (BOS). An approximate 40 per cent increase in oil production has been sustained, compared to control operations on the same well, for eighteen months.

The thrust to introduce pilot and field programs of BOS is compelling. BOS shares the advantages common to all biotechnologies in exploiting the extraordinary growth potential of microorganisms, providing flexibility through the extreme diversity of microbial metabolites and using cheap feedstocks. The BOS process generates ultramicrocells from those bacteria present naturally in the reservoir to be treated. This promotes injectivity, dispersion and persistence of the BOS system in the extreme environments which characterise petroleum reservoirs. The nutrients injected with the ultramicrocells result in metabolites forming within the bacterial cell surface. These metabolites cause re-profiling of the formation through the generation of emulsions and the development of concentrated surfactants at the oil-water interface.

Ecological strategies designed to negate previously documented problems in the application of microbial EOR have been shown to be effective in laboratory experiments and field applications. Overcoming environmental extremes and developing persistence of beneficial organisms have been given special attention.