ADVANCES IN MICROBIOLOGY TO ENHANCE OIL-RECOVERY

Microbial experiments to study enhanced oil recovery have generally been conducted using vegetative microorganisms and one-dimensional laboratory models. With the financial support of the Alberta Oil Sands Technology and Research Authority (AOSTRA), we have developed a procedure utilizing microorganisms called ultramicrobacteria (UMB) to assist in oil recovery by virtue of their growth properties. UMB or starved bacteria (.2-.3 /μm) have the ability to penetrate deep into model rock cores and respond to nutrient stimulation by effectively plugging these matrices by cell growth and polymer production. Vegetative cells or full-size cells tend to form "skin plugs" at or near the well bore. Initial UMB core studies in 5-cm and 10-cm sandstone cores were one-dimensional with unidirectional flow. To simulate reservoir conditions, UMB experiments were conducted in a pressure vessel, 45 cm in diameter x28 cm in height. In the first experiment a homogeneous sandpack was used, in the second a heterogeneous sandpack was used. Our experiments to date have shown (1) penetration of UMB, resuscitation upon nutrient stimulation, and reduction in permeability in homogeneous sand packs and (2) that resuscitated UMB preferentially plug the high-permeability zone by virtue of their growth properties and extracellular polysaccharide (polymer) production. © 1990 Humana Press Inc.