A new express method aimed to evaluate the necessity and order of converting existing wells into injection is proposed. The calculated time required to compensate oil production loss due to well conversion by oil production increase from a nearly wells as a result of water injection is used as a ranking criterion. The method is adapted to the development of reservoirs without an active aquifer and could be widely applied to the oil fields under high rate of drilling. The results of the method application were compared with reservoir simulation data and showed high level of convergence, that proves the efficiency of the technique proposed.