RU2468181C1 - Casing pipe centraliser - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: casing pipe centraliser comprises centralising metal plates fixed on rings and a stop ring for fixation of a centraliser on a casing string. On the inner surface of centralising plates there are hollow elements fixed, made of an elastic semipermeable material, the inner cavity of which is filled with a water-swellable polymer, at the same time the stop ring is arranged with rounded edges.

EFFECT: minimum diametre of a centraliser as a string is lowered into a well and maximum diametre after its lowering, and when cementing an inclined or horizontal borehole, efficient centralising of a casing string, reduced risk of centraliser damage in process of lowering.

2 dwg

Description

The invention relates to the construction of wells and can be used in the layout of the casing or liners for fastening oil and gas wells, as well as sidetracks.

To improve the quality of well attachment, especially in directional wells, casing must be centered.

Rigid centralizers can be used to center the casing, fixed to the casing [L.N. Shadrin. Technology and organization of well fixing. M., Nedra, 1975, p. 255]. The disadvantage of rigid centralizers is the deterioration of the casing patency during its descent, especially in places of narrowing or kinking of the well profile.

Closest to the proposed technical essence and the achieved effect is a spring centralizer [Reference for mounting oil and gas wells. M., Nedra, 1977, p. 98], in which metal plates mounted on rings are used as a centering element. The centralizer is fixed to the casing using a special retaining ring, which ensures a safe casing descent through the narrowing points due to the compression of the centering plates and the reduction of the centralizer diameter.

The disadvantage of the centralizer prototype is the low efficiency in centering casing strings.

The invention is directed to the creation of a centralizer for a casing string having a minimum diameter when lowering the string into the well and maximum after lowering it and when cementing an inclined or horizontal wellbore.

The problem is achieved in that in the casing centralizer, including centering metal plates fixed to the rings, and a retaining ring for fixing the centralizer to the casing, according to the invention, hollow elements made of elastic semipermeable material are fixed on the inner surface of the centering plates, the inner cavity of which filled with water-swelling polymer, while the retaining ring is made with rounded edges.

The design and principle of operation of the casing centralizer is illustrated by drawings, where in Fig.1 shows a General view of the device, Fig.2 is a section along the line aa.

The casing centralizer includes rings 1 on which the centering metal plates 2 are fixed, a retaining ring 3 is placed between the rings 1. Hollow elements 4 are made on the inner surface of the centering metal plates 2, made of elastic semi-permeable material, the inner cavity of which is filled with water-swelling polymer 5.

Centralizer casing works as follows.

In the process of lowering the casing string into the well, centralizers are installed on the casing so that, after the casing string is lowered, the centralizers are located at predetermined intervals of the well. The presence of rounded edges of the retaining ring will prevent the destruction of the elastic semipermeable material when the centralizer is moved relative to the retainer ring when the casing is lowered.

In the process of lowering the casing, the centralizer is in the transport position and secured to the casing with a retaining ring 3. The internal cavities of the elements 4 of elastic semi-permeable material are filled with water-swelling polymer 5, so the centering metal plates 2 have a minimum outer diameter, which ensures unhindered casing running into the well to design depth. In this case, the metal plates 2 protect the hollow elements 4 from destruction during friction of the casing string against the well walls. After the column is lowered during washing of the well and preparing it for cementing, the liquid diffuses through the semi-permeable faces of the hollow elements 4 from the elastic semi-permeable material into the elements and, interacting with the water-swelling polymer 5, causes it to swell. The swelling pressure is transmitted to the metal plates 2, which go into working condition and center the casing. Thus, by the beginning of cementing, the casing will be centered in the well with any angle of inclination, including wells with horizontal laying.

The use of this device in comparison with existing centralizers allows you to more efficiently center the casing and improve the quality of cementing of the casing due to:

- forced centering of casing strings adjacent to the wall of the well;

- better centering of casing strings in wells with any trajectory and more complete replacement of drilling fluid with cement mortar.

In addition, the use of the proposed centralizers will reduce the risk of destruction of the centralizers during their descent.

Claims (1)

A casing centralizer, including centering metal plates fixed to the rings, and a circlip for securing the centralizer to the casing, characterized in that hollow elements made of elastic semipermeable material are fixed on the inner surface of the centering plates, the inner cavity of which is filled with a water-swelling polymer, this retaining ring is made with rounded edges.

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