RU2773489C1 - Retractable casing centralizer - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the oil and gas industry and can be used for cementing casing strings during the construction of wells having a variable diameter. The casing string centralizer includes centering metal plates fixed evenly around the perimeter on the upper and lower rings, restrictive upper and lower rings installed on the casing string above and below the centralizer, with cavities. The upper restrictive ring is made with an annular inner recess facing towards the centralizer ring, which is inserted into the annular recess of the upper restrictive ring with the possibility of longitudinal movement under the action of expanding metal plates and fixation in this position. The upper ring has a thickening in which a radial groove is made, in which the retaining ring is installed. In the central part of the centering metal plates, a recess is made with the possibility of installing a steel ring into it.

EFFECT: increased reliability of operation of the casing string centralizer and expansion of its operational capabilities due to the possibility of free passage in narrow sections and exit in the working position in the extended section of the wellbore, isolated by the presence of shafts with varying diameters.

1 cl, 7 dwg

Description

The invention relates to the oil and gas industry and can be used for cementing casing strings during the construction of wells having a variable diameter.

Known casing centralizer with variable geometry (patent RU No. 2473777, IPC E21B 17/10, publ. spirals on the body surface, wherein the inner cavity of the centering elements is filled with a water-swellable polymer, and the outer side faces of the elastic centering element are made semi-permeable.

The disadvantages of this design are the difficulty in manufacturing hollow semi-permeable faces, the high cost of materials, both the centralizer itself and the swelling materials. Due to the uncontrolled expansion of the water-swellable material, there is no guaranteed casing centering.

Also known is a casing centralizer (patent RU No. 2468181, IPC E21V 17/10, publ. 27.11.2012, bull. No. 33), including centering metal plates fixed on the rings, and a retaining ring for fixing the centralizer on the casing, while on the inner surface of the centering plates, hollow elements are fixed, made of an elastic semi-permeable material, the inner cavity of which is filled with a water-swellable polymer, while the retaining ring is made with rounded edges.

The disadvantages of this design are also the difficulty in manufacturing hollow semi-permeable elements, the high cost of materials, both the centralizer itself and the swelling materials. Due to the uncontrolled expansion of the water-swellable material, there is no guaranteed casing centering.

The closest in technical essence and achieved technical result is the casing string centralizer (patent RU No. 2640849, IPC E21V 17/10, 17/1042, 14/1078, publ. 12.01.2018, bull. No. 2), including centering metal plates, fixed evenly around the perimeter on the rings, retaining (restrictive) rings fixed on the casing, and cavities filled with water-swellable polymer, moreover, retaining (restrictive) rings are installed above and below the centralizer, and cavities for water-swellable polymer are made in the form of annular internal selections in the retaining rings facing the rings of the centralizer, which are inserted into the annular selections of the retaining rings with the possibility of longitudinal movement under the action of an expanding water-swellable polymer.

The disadvantages of this centralizer are the high cost of materials, both the centralizer itself and the swelling materials, as well as the presence of a water-swellable polymer that sets the centralizer blades in motion, which requires a sufficiently long time to activate and swell, and therefore there is a possibility of incomplete opening of the centralizer blades to required diameter in the process of running and cementing the wellbore.

The technical objectives are to increase the reliability of the casing string centralizer and expand its operational capabilities due to the possibility of free passage in narrow sections and exit in the working position in the expanded section of the wellbore, isolated by the presence of shafts with varying diameters.

Technically, the tasks are solved by a sliding centralizer for the casing string, including centering metal plates fixed evenly around the perimeter on the upper and lower rings, restrictive upper and lower rings installed on the casing string above and below the centralizer with cavities.

What is new is that the upper restrictive ring is made with an annular internal selection facing the centralizer ring, which is inserted into the annular selection of the upper restrictive ring with the possibility of longitudinal movement under the action of expanding metal plates and fixation in this position, and a thickening is made on the upper ring, in which a radial groove is made, in which a locking ring is installed, while in the central part of the centering metal plates a recess is made with the possibility of installing a steel ring into it.

In FIG. 1, 2 shows the casing centralizer in the transport position.

In FIG. 3, 4 shows the casing centralizer in working position during cementing.

In FIG. 5, 6, 7 shows the operation of the centralizer inside the well.

The retractable casing centralizer consists of centering metal plates 1 (Fig. 3), evenly fixed along the perimeter on the upper 2 (Fig. 1, 3) and lower 3 rings, restrictive upper 4 and 5 (Fig. 3) lower rings installed on the casing string 6 (Fig. 1, 3) and located above and below the centralizer, for example, using locking screws 7 (Fig. 1, 2). In the upper restrictive 4 (Fig. 1) ring, a cavity 8 (Fig. 3) is made in the form of an annular inner sample facing the upper ring 2 (Fig. 1) of the centralizer. The upper ring 2 of the centralizer is inserted into the cavity 8 (Fig. 3) of the restrictive ring 4 with the possibility of longitudinal movement under the action of expanding centering metal plates 1 made of spring steel and tending to assume a curved position, and fixing in this position.

Moreover, on the upper ring 2 (Fig. 1) there is a thickening (not marked in Fig. 1-4), in which a radial groove 9 (Fig. 4) is made, in which, in turn, a retaining ring 10 is installed. centering metal plates 1 (Fig. 3) a recess 11 (Fig. 1) is made with the possibility of installing a steel ring 12 into it, which holds the centering metal plates 1 (Fig. 3) in the transport position (compressed) up to a certain point.

Sliding centralizer for casing works as follows.

In the process of lowering the casing string 6 (Fig. 5) into the well, centralizers are installed on it with a steel ring 12 pre-dressed on the centering metal plates 1, which keeps the plates 1 from straightening until the required section of the wellbore is reached, at a calculated distance and are fastened with restrictive 4 and 5 rings, for example, using locking screws 7. At this time, the centralizer is in the transport position, the diameter along the centering metal plates 1 is equal to - d1, which allows you to freely lower the casing string into the well to the narrowed section. After reaching the centralizer on the casing 6 (Fig. 5) to the point of narrowing, the centering metal plates 1 of the centralizer are compressed and the steel ring 12 comes out of the recess 11. Thus, the steel ring 12 remains in the narrowed area, and the casing 6 with the centralizer continues to move down (Fig. 5). After passing the narrowed section, the casing string 6 with the centralizer reaches the expanded section of the wellbore (Fig. 6), getting into the expanded section of the wellbore, the centering metal plates 1 of the centralizer are straightened to a diameter - d2, equal to the diameter of the wellbore in this section. In this case, the upper ring 2 of the centralizer extends in the direction opposite to the restrictive ring 4 until the stop ring 10 exits the radial groove 9, thereby fixing the centering metal plates 1 in the expanded state, which in turn reliably centers the casing string 6 relative to the walls of the well in extended section of the trunk. Thus, the casing string 6 (Fig. 7) by the beginning of cementing will be centered in a well with varying diameters, with any angle of inclination, including in horizontal wells.

The proposed retractable casing centralizer is easy to manufacture, allows you to freely lower the casing string into the well and ensure its centering during casing string cementing. Also, the sliding centralizer allows you to expand the operational capabilities due to the possibility of free passage in narrow sections and exit in the working position in the extended section of the wellbore, isolated by the presence of shafts with varying diameters.

Claims (1)

Sliding centralizer for casing, including centering metal plates fixed evenly along the perimeter on the upper and lower rings, restrictive upper and lower rings installed on the casing at the top and bottom of the centralizer, with cavities, characterized in that the upper restrictive ring is made with an annular inner a selection facing towards the centralizer ring, which is inserted into the annular selection of the upper restrictive ring with the possibility of longitudinal movement under the action of expanding metal plates and fixation in this position, moreover, a thickening is made on the upper ring, in which a radial groove is made, in which the retaining ring is installed, at the same time, a recess is made in the central part of the centering metal plates with the possibility of installing a steel ring into it.

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