a device for improving recovery of hydrocarbons through a well by creating , regulating and maintaining under the device a calculated bottomhole pressure at a desired level and creating above the device a two - phase gas - liquid homogenous flow for efficient lifting of hydrocarbons to a surface , the device has a body having a central through - going opening with a shape corresponding a shape of a laval nozzle and with a cross section which changes steplessly and gradually , and a mandrel attachable to a tubing and associated with the body without interfering with a flow of fluids .