Visualisation of bacterial degradation and mobilisation of oil in a porousmedium

Bacterial interaction with oil and sea water, in a porous medium, was studi ed using a transparent micro model mounted on a cybernetic-controlled posit ioning board of an inverted microscope. This was interfaced with computer-o perated image analysis and surveillance equipment. Consecutive flooding of the model allowed oil to become trapped by capillary forces. Hydrocarbonocl astic bacteria were inoculated. The interaction of biofilm and oil was moni tored during a period of 25 days, while mineral salts were supplied intermi ttently A unique feature of biofilm behaviour was discovered. The phenomeno n is discussed, and calculations are presented. A possible explanation of t he phenomenon appears to be local reductions of the surface tension. The ph enomenon helps explain why bacteria are able to mobilise oil trapped by cap illary forces without reducing the interfacial tension to a level that lead s to an increase in the capillary number sufficient to explain incremental oil recovery. The experimental design is believed to be suitable for studyi ng biofilm behaviour on the pore level.