THE USE OF BACTERIA TO REDUCE WATER INFLUX IN PRODUCING OIL-WELLS

This paper reports the results of a laboratory investigation evaluatin g the use of bacteria to reduce water production from oil wells. The o bjectives are to show that bacteria can be used to form in-depth stabl e plugs in porous media, to show that the bacterial plug can reduce ef fectively the amount of water being produced in oil wells by preferent ially reducing the relative permeability of water, and to report brief ly on the economic value of such a treatment. Bacterial strains for te sts in a physical model of a producing well and near-wellbore region w ith flow in two dimensions were selected based on results in linear-fl ow sandpacks. Results from the linear sandpacks showed that in-depth p lugs can be formed in porous media by the injection of one pore volume of nutrient. The pretreatment sandpack permeability of 6,600 md was r educed to a stable 200 md after one treatment. Bacterial injection and incubation in the two-dimensional physical model resulted in a 47% de crease in water cut (from 95% pretreatment to 50% post-treatment). The experiments also show that the bacterial plug preferentially reduces the relative permeability of water in the presence of both oil and wat er. A preliminary economic evaluation was performed using field data a nd laboratory results. Although no attempt was made to economically op timize the laboratory system, an extrapolation to field values shows e conomic potential.