RU2684626C1 - Sectional separating plugs for cementing of stepped casing strings - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to sectional separating plugs for cementing of stepped casing strings. Sectional separating plug for cementing of stepped casing string consists of a core and a ferrule connected to it and elastic collars having sealing and conical separating parts. Collars from inside are spring-loaded outwards by plates. Tip is equipped with elastic centralizers. Axis distance between upper collar and bottom centralizer is larger than maximum inner diameter of casing string.EFFECT: technical result is increase in reliability.1 cl, 2 dwg

Description

The invention relates to the field of construction and operation of oil and gas wells, in particular to devices for cementing casing strings.

Known cementing plug E.M. Suleymanova (copyright certificate SU No. 1500763, IPC Е21В 33/16, published in bulletin No. 30 of 08/15/1989), including an elastic case with a blind axial hole made in it and cuffs fixed to the outer surface of the case, with the aim To increase the reliability of its operation in stepped columns, the casing is made in the form of a cone, the base of which is located on the side of a blind axial hole, and the diameters of the cuffs are successively reduced from top to bottom for different diameters of the columns.

The disadvantages of this design are:

- lack of centering relative to the walls of the casing string of large diameter, which leads to skewing of the cork and mixing squeezing fluid with cement mortar, which in turn will lead to incomplete pushing of cement into the annulus;

low-quality cleaning of the walls of the casing from cement;

- the probability of non-receipt of the “stop” pressure if the plug approaches the shoe of the column with a bias.

Known dividing cementing plug (copyright certificate SU No. 1673727, IPC ЕВВ 33/16, published in Bulletin No. 32 of 08/30/1991), containing a housing with elastic sealing cuffs installed on it, having blind recesses on its surface, while In order to increase the efficiency of liquid separation in the casing of two-dimensional casing pipes, the cuffs are made of the same diameter and have through the wedge-shaped grooves on the peripheral part, the tops of which are located on the circumference of a larger sealable size, while the blind recesses are made They are wedge-shaped on both sides of each cuff, their vertices are located on the circumference of a smaller compacted diameter, and the arched bases are on a circle whose length corresponds to a smaller compacted size, increased by the length of these arcuate bases.

The disadvantages of this design:

- the presence of wedge-shaped grooves can lead to mixing squeezing fluid with cement mortar;

- wedge-shaped grooves also reduce the centering of the cork relative to the walls of the column.

Closest to the technical nature of the invention is a sectional separation plug for cementing stepped casing strings (copyright certificate SU No. 1408052, IPC ЕВВ 33/16, published in bulletin No. 25 dated 07/07/1988), consisting of a core and associated tip and elastic cuffs of different diameters, having a sealing and conical dividing part, while in order to increase the reliability of the cork by eliminating skew when the cuffs exit into the column section of a smaller diameter by folding the cuffs into uniform corrugations in the areas of the cuffs intended to form a local deflection towards the cork axis when the cuff exits into the column section of a smaller diameter, blind grooves are made on the outer surface of the cuff separation part along the cone generatrices.

The disadvantage of this design is the lack of centering relative to the walls of the casing of large diameter, which leads to skewing of the cork and mixing of the squeezing fluid with the cement mortar, which in turn will lead to incomplete pushing of cement into the annulus.

The technical task of the invention is to increase the reliability of the separation tube in the stepped casing strings due to the reliable centering of the tube in different diameters of the columns, which is ensured by the longer tube length relative to its diameter and guaranteed pressing of the tube cuffs to the walls of the column of both small diameter and large.

The technical problem is solved by a sectional separation plug for cementing stepped casing strings, consisting of a core and associated tip and elastic cuffs having a sealing and conical separation part.

What is new is that the cuffs are spring-loaded outwardly by plates and the tip is provided with elastic centralizers, and the distance along the axis between the upper cuff and the lower centralizer is greater than the maximum inner diameter of the casing.

In FIG. 1 shows a separation plug in a small diameter casing, FIG. 2 - separation plug in the casing of a larger diameter.

Sectional separation plug for cementing stepped casing consists of a core 1 (Fig. 1 and 2) and associated tip 2 and elastic cuffs 3 having a sealing 4 and a conical 5 dividing part. The cuffs 3 are spring-loaded outwardly by the plates 6, and the tip 2 is provided with elastic centralizers 7.

Sectional separation plug for cementing stepped casing works as follows.

From the cementing head, the separation plug is pressed into the casing by a fluid flow at the boundary of the shared fluids. Elastic centralizers 7, mounted on the tip 2, and elastic cuffs 3 together with spring plates 6 are installed on the core 1, while compressed to the inner diameter of the casing string d1 (Fig. 1). The tapered spacer part 5 of the cuff serves to simplify the installation of the plug in the cementing head, as well as to guide the plug during movement. The sealing separation part 4 provides the necessary alignment and serves to better separate the cement slurry and squeezing fluid. In this form, the separation plug is pushed to the casing of larger diameter d2. Upon entering this column, the elastic cuffs 3 under the action of the spring plates 6 are expanded to an inner diameter d2 (Fig. 2). The elastic cuffs 7 also expand and begin to center the separation tube relative to the walls of the casing of larger diameter d2. For better centering of the plug in the casing of a larger diameter d2, the distance H along the axis between the upper cuff 3 and the lower centralizer 7 is larger than the maximum inner diameter of the casing d2. This condition eliminates the possibility of skewing the plug inside the column during the cement grouting process.

The same dividing plug can be used for cementing shanks to prevent the use of two plugs. First, the cuffs of the separation plug are compressed, and the plug passes through the drill string, on which the liner is lowered, then, falling into the liner, the same plug extrudes the cement mortar to the shoe of the liner.

The proposed design allows to increase the efficiency of the separation tube in the stepped casing strings due to the centering of the tube in different diameters of the columns, which is ensured by the longer tube length relative to its diameter and guaranteed pressing of the tube cuffs to the walls of the column of both small diameter and large.

Claims (1)

Sectional separation plug for cementing stepped casing strings, consisting of a core and associated tip and elastic cuffs, having a sealing and conical dividing part, characterized in that the cuffs are spring-loaded from the inside by plates and the tip is provided with elastic centralizers, with an axial distance between the upper the cuff and lower centralizer are larger than the maximum inner diameter of the casing.

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