RU162489U1 - DRILL RIG ELECTRICAL SEPARATOR - Google Patents

Abstract

Drill string electric separator, including upper and lower sub, interconnected by a special conical thread with an electrical insulation coating, characterized in that an unloading groove is made on the coupling part of the electric separator, and the conical thread has a taper of 1: 8 and is made in 12 mm increments, the radius of the troughs of the thread is 3 mm, and the radius of the vertices of the thread is 1.4 mm.

Description

The invention relates to the field of geophysical research of wells and is intended for use as part of cableless telemetry systems for electrical isolation of the drill string and to provide two-way communication of the telesystem with ground equipment.

Currently used electric pipe drill pipe splitters include upper and lower sub, interconnected by a special tapered thread with an insulating gasket. Inside and outside the dividers are covered with electrical insulation material (ed. St. USSR No. 994704, MKI E21B 47/02, application form 31.12.80; patent for PM No. 17196, IPC E21B 47/00, application form 23.10.00; patent for PM No. 37138 IPC E21B 17/12, claimed July 15, 03; patent for PM No. 54397, IPC E21B 44/00, claimed 08.02.06, etc.).

Due to the fact that even the most high-strength dielectrics are inferior to high-strength steels used in the dividers in terms of the set of mechanical characteristics (strength, hardness, ductility, impact strength), the special thread of the separator remains the weakest link in the layout of the bottom of the drill string.

Attempts to modernize special threads by changing its parameters are made in the patents for inventions No. 2333356 IPC E21B 47/12, decl. September 13, 2008, No. 2425214 IPC E21B 47/12, declared 04.25.2007, No. 2307931 IPC E21B 47/12, declared 01/27/2006, No. 2250994 IPC E21B 47/12, declared 01/15/2004, etc.

In these patents, designers try to optimize the taper and thread profile to increase the strength and reliability of the separator.

In patent No. 2307931 IPC E21B 47/12, decl. January 27, 2006 proposed the use of tapered threads with a rectangular profile of turns. Profile height decreases with increasing thread diameter.

In this design, the transmission of torsion moment and axial loads occurs only through the end surfaces of the threads, the area of which is several times smaller than the interface, and the bending stresses arising in such a connection when drilling curved wells will be concentrated in the area of the outlet of the nipple from the coupling, which reduces the strength and separator reliability.

The closest technical solution to the proposed one is the electric separator of the drill string, described in the patent for utility model No. 136085, IPC E21B 47/12, decl. 08/28/2013. The electrical separator sub is screwed on a special conical thread with a pitch of 10 mm, taper 1: 6, while the radius of the troughs and vertices of the thread profile is 1.5-2 mm.

The manufacture of the radii of the vertices of the thread profile of the same size with the radius of the depressions leads to a decrease in the height of the thread profile, and most importantly reduces the width of the overlap of the thread profile. Accordingly, the interface area of the metal elements of the nipple and the coupling is reduced, which increases the load on the dielectric gasket and reduces the bearing capacity of the separator. In addition, the radius of the hollows of the thread of 1.5-2 mm creates a concentration of stresses in the nipple, especially in the last turn associated with the coupling. When drilling curved wells, bending stresses will be concentrated in this last turn in the zone of exit of the nipple from the coupling, where a sharp change in the rigidity of the node occurs, which reduces the strength and reliability of the separator.

The problem solved by the creation of a utility model is to increase the strength and reliability of the separator.

The required technical result is achieved by the fact that on the coupling part of the electric separator, including the upper and lower sub, interconnected by a special conical thread with an electrical insulating coating, an unloading groove is made, and the conical thread has a taper of 1: 8 and is made in increments of 12 mm, with the radius of the troughs of the thread is 3 mm, and the radius of the vertices of the thread is 1.4 mm.

In FIG. 1 shows an electrical isolator.

The electrical separator includes sub 1 and 2 connected by a tapered thread 3 with an electrical insulating coating 4. An unloading groove 5 is made on the coupling sub 1 in the end zone of the mating nipple part of the sub 2.

Unloading groove 5 allows you to reduce stress in the area of a sharp change in the rigidity of the node in the place of exit of the nipple from the coupling. When assembling the separator in the layout of the bottom of the drill string, the unloading groove 5 can play the role of a groove under the clamp or elevator.

The use of the discharge groove 5 on the coupling and the increase in the radius of the troughs of the thread to 3 mm reduces the stress concentration in the nipple in the clipping zone of the coupling and increases the endurance of the separator.

Reducing the radius of rounding of the threads to 1.4 mm increases the overlap size of the metal elements of the profile and the coupling of the nipple and provides increased tensile strength. Reducing the taper of the thread from 1: 6 (in the prototype) to 1: 8 and increasing the pitch of the thread to 12 mm, allows to increase the surface area of the dielectric gasket between the contacting elements by 20-25% and, accordingly, increase the shear strength of the splitter joint.

An example of a specific implementation of the proposed technical solution is a dielectric pipe separator for the well complex SOTEKS-178. This separator with an outer diameter of 178 mm consists of two sub-units connected through a dielectric gasket on a tapered thread with a 1: 8 taper, made in 12 mm increments. The radius of the troughs of the thread is 3 mm, and the radius of the vertices of the thread is 1.4 mm. An unloading groove is made on the coupling sub, which allows bending loads in the nipple to be reduced when drilling curved wells. This groove is also used to install the clamp during assembly of the BHA.

The selected thread parameters are determined by the restrictions on the geometric and operational characteristics of the separator.

Geometric constraints are:

- the diameter of the inner flow part of the separator should provide a drilling fluid flow rate of not more than 10-12 m / s. A decrease in diameter causes a quadratic increase in flow velocity and leads to an increase in the fourth degree of abrasive and cavitation wear of the internal tract;

- the outer diameter of the separator, as determined by the BHA design for well drilling;

- the thickness of the inner insulating layer necessary to ensure operational resistance to waterjet wear and pressure and temperature drops;

- the thickness of the outer insulating layer, determined by the requirements for ensuring operational reliability during friction against the walls of the well.

Operational restrictions are the loading conditions of the separator:

- axial loads up to 300 kN during drilling, up to 1000 kN when lowering and raising the string, and up to 2000 kN during emergency tacking;

- rotor torsion moment up to 30 kN · m;

- jet downhole torque up to 2.5 kN · m;

- bending in a curved well up to 3 deg / 10 m or with a bending radius of the well less than 200 m;

- tensile loads from the action of drilling fluid pressure up to 20 MPa.

The size ratio (pitch 12 mm, radius of the cavity of the profile 3 mm, radius of the tip of the profile 1.4 mm, taper 1: 8) allows you to optimize the stresses that occur in the special thread unit of the separator with a diameter of 178 mm in accordance with operating loads.

A further increase in thread pitch to 13 or more millimeters is impractical, because this will increase the difference in the thicknesses of the parts in the thread area and decrease the rigidity of the bending unit as a whole. In addition, in this case, the number of threads will decrease and, accordingly, the load on each thread will increase.

A further decrease in the taper of the joint to 1: 9 or less is impractical due to technological difficulties when threading, due to the lack of holders for threading inserts on the market with the required length and rigidity. The manufacture of special holders of the required cantilever length (more than 350 mm) leads to a decrease in their rigidity and deformations during thread processing, since the diameter of the mandrel is limited by the initial minimum diameter of the tapered thread. Errors appearing when threading the coupling and the nipple will lead to uneven loading of the turns along the length of the threaded part.

The operating experience of the dielectric tube separator for the SOTEKS-178 downhole complex has shown its high performance and reliability.

Claims (1)

Drill string electric separator, including upper and lower sub, interconnected by a special conical thread with an electrical insulation coating, characterized in that an unloading groove is made on the coupling part of the electric separator, and the conical thread has a taper of 1: 8 and is made in 12 mm increments, the radius of the troughs of the thread is 3 mm, and the radius of the vertices of the thread is 1.4 mm.

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