RU2059056C1 - Device for aligning a string of casing - Google Patents

Abstract

FIELD: oil production. SUBSTANCE: device for aligning a string of casing has a cylinder fixed rigidly on casing body, and aligning elastic elements-flags provided with spring-loaded bows and revolution axles, installed in lateral openings of the cylinder. When a string of casing descends in well, the flags are unwrapped along generatrix pipe to occupy smaller covering radius, column is put easily. If one will rotate the column, the flags are put in positions of maximum covering radius, thus casing body is cemented in well borehole. EFFECT: high accuracy. 4 dwg

Description

 The invention relates to the mining industry, in particular to casing fastening of wells during their drilling for oil and gas.

Known centralizer, consisting of two steel rings, which are welded spring arched strips [1]
The disadvantages of this design are low centering ability, limited patency of the casing during cementing and high metal consumption.

Known centralizer, in which there are centering elements in the form of flags associated with the housing axis of rotation, and the site of the forced rotation of the flags [2]
The main disadvantage of this technical solution is the need to control its operation remotely, that is, by a signal from above, since the centralizer is designed to center (position) the device in the well. Such a solution cannot be extended to casing centering control in the well.

 The aim of the invention is to increase the centering ability and patency of the casing along the wellbore.

 The goal is achieved in that in the centering device containing the cylinder fixed rigidly on the body of the casing and the centering elastic elements, rotary centering flag elements are used, having spring arcs and axis of rotation installed in the side holes of the cylinder, and the cylinder with side holes is worn on the body of the pipe and is fixed on it by any known method. The flags with the outer surface are in contact with the walls of the borehole and, when the column moves, progressively or rotationally unfold in the direction opposite to the movement. Moreover, if the flags occupy a vertical position that coincides with the generatrix of the casing, then the external radius of coverage of the flags is minimal. If the column is rotated, then the flags occupy a position perpendicular to the generatrix of the casing. In this case, the radius of the flags is maximum. Depending on the length of the flags, the bending of the arc and the selection of their deformation elasticity, this radius may be less, equal to or slightly larger than the radius of the well, depending on the requirements established by the technology of fastening the wells. Therefore, when the casing is lowered into the well, the flags are deployed along the forming pipes, occupying a smaller radius of coverage, the cross-country ability of the string is increased, the restriction on the speed of descent is removed. If the column is rotated, then the flags occupy the position of the maximum radius of coverage, so the body of the casing is centered in the wellbore.

 There must be at least three flags in one centralizer.

 It is known that if the casing is rotated with a certain allowable number of revolutions while the cement slurry moves through the annular space, the conditions for the most complete removal of drilling mud residues in the well are improved, which leads to an increase in the quality of centering.

 Figure 1-4 shows a diagram of a device for centering a casing string.

 A cylinder 2 is put on the casing 1 (Fig. 1) and fixedly fixed on it by fastening elements 3. In the lateral openings of the cylinder, which should be at least three, flags 4 are installed, having an axis of rotation containing two parts of different diameters: a larger a and a smaller b and an outer arcuate surface (FIG. 2). When transferring any force to the arc of the flag 4, for example, when the casing, which is supported by the arc of the flag on the wall of the well, moves relative to the front, then the flags are deployed in the direction opposite to the movement of the column. Such effort can be sequentially transmitted to each flag during further casing movement.

 So, when the column moves during its descent along the wellbore, the flags are located along the generatrix of the pipe body and occupy a position corresponding to the minimum radius of coverage. When the column rotates, the flags, in succession in contact with that part of the borehole wall, to which the casing pipe body is closer, unfold perpendicular to the pipe body forming, occupying the position with the largest radius of coverage, and center it relative to the wellbore. This rotation of the casing is combined in time with the movement of the cement slurry along the annular channel.

 However, rotation of the casing is not always possible. For example, when curving wellbores, in complicated trunks, in deviated or horizontal wells. In this case, a centering device is used that allows the casing to be centered only by turning it one or more revolutions with a minimum speed. On the body of the pipe 1, cylinder 2 is fixed by fastening elements, having side holes (at least three) for most of the axis of rotation a of flag 4. On cylinder 2, a clip 5 is worn with freedom of rotation. Flag 4 has an arcuate outer surface and an axis of rotation consisting of two parts axis a larger diameter and axis b of smaller diameter, located relative to each other with eccentricity. The axis of rotation of the flags are located in the side openings of the casing 5. The cylinder 2 assembled in a single unit, the cage 5 and the flag 4, fixed on the body of the casing, form a centering device.

 The device (figure 3 and 4) works as follows.

 When the casing moves relative to the wellbore translational or rotational, it is sufficient to exert an effort from the borehole wall on the arc of any flag, after which it turns in the direction opposite to the casing movement. Other flags of this centralizer unfold simultaneously with it, since the force from the expanding flag through the axes a and b and the clip 5 is transmitted to each flag.

 To bring the device from the transport position, when the flags are located along the generatrix of the pipe, to the working position, so that the flags are perpendicular to the generatrix of the pipe, which corresponds to the largest radius of coverage, it is enough to make several turns of the casing at any speed at any time before or during cementing.

 The advantage of the proposed design of the device for centering the casing strings is that it allows: by giving the flags high elastic properties to minimize the eccentricity of the casing strings relative to the wellbore; by transferring force to one of the flags and turning it, turn the rest in the same direction (Figs. 3 and 4); rotate the casing with any productivity in order to most completely remove the residual drilling fluid (Fig.1, 2), to ensure centering of the casing in any wells; to provide high cross-country ability of casing strings during their descent, reducing restrictions on the speed of descent; reduce metal consumption for the manufacture of a centering device.

Claims (1)

 DEVICE FOR CENTERING CASING COLUMNS relative to the axis of the well, containing a cylinder rigidly connected to the body of the centered pipe, centering elastic elements in the form of flags connected to the cylinder by the axis of rotation, and a node for forced rotation of the flags, characterized in that the axis of the flags are made in the form of two eccentric parts of equal diameter, and the knot of forced rotation of the flags in the form of a clip freely mounted on the housing with side holes, the axis of the small diameter flags being located in the latter.

Images