SU825828A1 - Device for drilling offshore wells with reverse flushing - Google Patents

Description

one

The invention relates to offshore drilling, in particular to drilling with the removal of backwash rock.

A device for drilling in the form of a pulp-raising column with a hydraulic ripper at the bottom is known. Directly above the hydrolayer, a mixer is installed, to the body of which the air duct is connected to the water pipelines, which are laid along the main pulp-lifting column.

The disadvantage of this device is the need to continuously adjust the modes of operation of the projectile as the depth of the well increases, as well as the impossibility of drilling in a rotational way due to the presence of three pipelines.

A device for back-flush drilling of offshore wells is known, comprising a drill string with a bit, a casing and an air supply pipe. The device provides rotational

drilling of solid bottom and with the airlift method of raising the pulp to the surface. The drill column with a chisel at the end is made up of two concentrically arranged pipes: a central pulp-raising and an outer air conductor joined by a mixer above the chisel. The well is cased along the casing as it is drilled. The annulus is filled with water 1.

The disadvantages of the known device are excessive costs.

5 times for tripping due to the fact that the drill pipe sections are not single, but consist of two rows of pipes; low prog-gus ability of a pulp-lifting column due to limited diameter.

Claims (1)

The purpose of the invention is to increase the efficiency of drilling and thinning of pulp removal. This goal is achieved by the fact that the casing string has windows that connect the casing with the external marine environment, and the drill string is made with holes located above the casing windows and below the sea level. The drawing shows the device in section. A device for backwashing drilling of offshore wells consists of a drill string 1 with a bit 2 located concentrically to the casing 3. In the upper part of the casing 3 there are pas: tubes 4 for supplying compressed air, and the annular space between the drill and garden columns is sealed Signals & 1m device 5, for example, rotating preventer. In the lower part, directly above the seabed bottom, the casing string 3 has through-through approx. 6, which imparts an intracavity cavity with the external marine environment. The drill string 1 is formed with holes 7, which are located above the windows of the casing 3 and below the sea level. Preparation for the operation of the device begins with the fact that the casing 3 is lowered to the bottom of the sea, and it is driven into the ground so that the windows 6 remain in the water, as close as possible to the bottom of the sea. Prevento b is installed on the upper end of the casing 3 with a pipe 4 intended for supplying compressed air to the cavity of the casing 3. Then the drill string 1 with a bit 2 consisting of separate pipes, including pipes with holes 7, is lowered into the casing string. The drill pipe with holes is placed in the drill string 1 so that the holes 7 are below the sea level, but above windows 6 of the casing 3 by an amount equal to or greater than the length of the drilling run (the length of the flight does not exceed the length of the lead pipe). The drill pipe with holes must be placed as deep as possible in the sea for the purpose of greater drilling efficiency. The minimum Ae depth of holes 7 beneath the sea level must be greater than the value of the discharge line above sea level. The device starts to work when simultaneously with the rotation of the drill string into the annular space between the casing 3 and the drill string 1, air is supplied iiepes pipe 4. Air pushes the water below the holes 7 of the drill string 1 | enters through the holes 7, into the drill string and is displaced with water located in the upper part of the drill string. At the top of the drill string 3, air-water is formed on the mixture, which is less dense than the water in the annulus. Therefore, from the annular space, water enters through the holes in the bit into the drill string, sucking pulp with broken rock from the intake. At the same time, water from the sea continuously flows into the casing 3 through the windows 6 and, together with the destroyed rock, flows to the surface through the drill string 1. After a well is deepened by a certain amount, depending on the length of the lead pipe, the drill string is expanded. For this, the drill string is raised from the Zabo so as to disconnect the drill pipe with holes 7 from it. Then between the drill string remaining in the well and the drill pipe with holes 7, a new drill pipe is expanded. This build-up allows maintaining a constant amount of hole depth 7 and, that cabOiiM, using a compressor of the same power. After the extension of the next drill string, the drilling cycle is repeated. The technical and economic efficiency of the proposed device is to increase the drilling rate due to better removal of the destroyed rock in the drill string, which is not limited in diameter, as well as to reduce the time for tripping operations. The invention The device for drilling with reverse flushing of offshore wells, containing a drill string with a bit, a casing and an air supply-pipe, is designed so that, in order to increase the efficiency of drilling and