•A down hole method for ultrasonic treatment is developed to enhance oil recovery on failing oil wells.•The method increases the permeability of the bottom hole zone and reduces blockages.•The method is simple, environmentally safe and is successful in up to 85% of cases.•The effect due to ultrasonic treatment lasts for 3–12months. A new method for the ultrasonic enhancement of oil recovery from failing wells is described. The technology involves lowering a source of power ultrasound to the bottom of the well either for a short treatment before removal or as a permanent placement for intermittent use. In wells where the permeability is above 20mD and the porosity is greater than 15% ultrasonic treatment can increase oil production by up to 50% and in some cases even more. For wells of lower permeability and porosity ultrasonic treatment alone is less successful but high production rates can be achieved when ultrasound is applied in conjunction with chemicals. An average productivity increase of nearly 3 fold can be achieved for this type of production well using the combined ultrasound with chemical treatment technology.