A method of reducing wax deposition in an oil wellbore tubing includes providing an aqueous bioslurry comprising at least one microbe capable of degrading paraffin wax at about 20-45° C. and a nutrient medium containing one or more carbon source and an oxygen slow-releasing compound. The method further includes providing an oil wellbore completion having a production tubing with an interior surface including a zone that is susceptible to wax deposition when the well is operated to produce oil. The method further includes, while oil production from the well is stopped, incubating the biological slurry in the wax-deposition zone tubing for a sufficient time to multiply the microbe(s) and form a biofilm on at least the wax-susceptible zone.