<p>The invention pertains to the oil and gas industry and can be used in the development of producing formations. A producing string (6) together with a sealing device (7) are lowered into a well (1) and the well (1) is divided into an upper cavity (8) and a lower cavity (9) with the aid of said sealing device (7) to establish a hydraulic connection between the well opening and the producing formation. The installation of equipment (10) and a check valve is carried out step by step. A washer fluid (4) is replaced by a washer fluid (15). The equipment (10) is passed through the sealing device (7) and the hydraulic connection between the well opening and the producing formation is re-established along the annular channel. The well (1) is deepened using the equipment (10) until an inflow of formation fluids occurs, the differential pressure in the well being adjusted during the process using the check valve and a blowout preventer. The equipment (10) is withdrawn from the lower cavity (9) of the well and the sealing device is closed so as to cut off the hydraulic connection between the well opening and the producing formation. The method increases the efficiency and quality with which technical operations can be carried out and prevents the undesired inflow of formation fluids.</p>
