Bacterial Processes for Improved Oil Recovery
Authors: Frick John R. 
Published: December 2007

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There is now, and has been for some 30 years, limited research in the area of bacteriological oil recovery. Several patent have been issued as a result of these works. However, concentrated effort is now being given to the problem of oil spills and their cleanup through bacterial methods. The time is right, therefore, to combine and accelerate our research in bacterial oil degradation, and to apply bacterial recovery methods. In this manner we can not only work toward improving the ecosystem but also derive new and economically feasible bacteriological oil recovery mechanisms. The purpose of this article is to briefly discuss bacteriological oil recovery, to stimulate thought, and to promote research in this area. promote research in this area. In the early 1940's, Zobell discovered that bacteria will release oil from sedimentary materials.'," In Dec., 1946, in conjunction with the American Petroleum Institute, he obtained a patent on a process Petroleum Institute, he obtained a patent on a process that involved the injection of anaerobic bacteria into an oil producing formation to increase oil recovery., He named the bacteria that he had isolated Desulfovibrio hydrocarbonociasticus, These bacteria are strict anaerobes and Zobell noted that they grow actively in salt solutions of 25,000 to 125,000 ppm dissolved solids. Also, they are able to tolerate high temperatures. In laboratory experiments Zobell found that the four mechanisms of bacterial oil release are:(1)production of gaseous carbon dioxide,(2)production production of gaseous carbon dioxide,(2)production of organic acids and detergents,(3)dissolution of carbonates in the rock, and(4)physical dislodgment of the oil.
Zobell found that bacteria preferentially consume normal paraffins. More recently, with gas chromatography and other tools, this finding has been reaffirmed.
Extensive tests of bacteria for oil recovery were made at the Bradford Laboratory of the Pennsylvania Grade Crude Oil Assn. during 1945 and 1946. The results were generally discouraging for bacterial applications in the Bradford area and it was therefore concluded at that time that field tests would not be feasible. However, this finding should now be reviewed and should not be assumed to hold true for present times and different locations. present times and different locations. So far, no results of field tests employing bacterial processes have been published in the U. S. literature. processes have been published in the U. S. literature. However, favorable results have been reported from tests conducted in Poland" and Hungary." The Polish observed oil production increases of 30 to 140 Polish observed oil production increases of 30 to 140 percent with pressure increases from 2 to 25 atm in percent with pressure increases from 2 to 25 atm in several shut-in wells. The pH of the reservoir water dropped from 8.7 to 6.4. There were small decreases in oil viscosity, and in some wells production increases continued for as long as 5 years. Also in Poland, bacteria of the Clostridium type have been isolated; these bacteria reduce heavy hydrocarbons in place to form lighter fractions and gases. Something of this nature could be of great significance to the Athabasca tar sands area. The possibility exists that bacteria can also be used for selective plugging. Since the bacteria and nutrients would be highly concentrated in thief zones, rapid, prolific growth would occur there. prolific growth would occur there. Plugging of the wellbore could be eliminated by separate-stage injection of spores and nutrients followed by a water pad to move the bacteria into the formation. Then a small amount of bactericide could stop the growth at the sand face. In this process the thief zone could be plugged, leaving the wellbore unaffected, and the sweep efficiency could be increased. Another possible application is in the underground production of water-thickening agents. production of water-thickening agents.
JPT
P. 1469