FIELD: earth or rock drilling.
SUBSTANCE: group of inventions relates to oil and gas industry and can be used in drilling and repair of wells with abnormally low formation pressure (ALFP). When implementing the method, a drill string with a working tool is lowered into the well, into which a device is installed, which includes a jet pump and a cup-type self-sealing packer element configured to rotate about the axis of the device while providing tightness and dividing the annular space of the well into a top and a bottom, active fluid flow is supplied to the device. One part of flow is directed into lower annular space for circulation in area of works, other part is directed to the jet pump, which lifts the passive medium along the lower part of the string from the work area and directs it to the surface, face is cleaned by moving the string downward, drilled and milled by rotating the string with the tool and moving it up or down. Active flow is supplied through the upper annular space, and the passive medium for carrying to the surface is directed to the upper part of the string, at that, providing the borehole fluid free circulation between the upper and lower annular spaces during the lowering and lifting operations and limiting it during the jet pump operation. Device comprises a valve for controlling circulation of well fluid above packer element, additional channel connected to the bypass channel, which begins on the outer surface of the device above the packer element, which is open during lowering and lifting operations and shut off with a valve when pressure increases in the upper annular space.
EFFECT: use of the invention reduces the labour input of the process while simultaneously reducing accident rate and minimizing the loss of drilling mud during operations in oil and gas wells with abnormally low formation pressure.
5 cl, 12 dwg
