SU909114A1 - Method of repairing casings - Google Patents

Description

(S) METHOD OF REPAIR OF COLUMN COLUMNS

one

The invention relates to casing repair technology and can be used in the oil and gas industry in repairing casing strings by installing expandable pre-fabrication patches in the repaired section of the casing.

Casing repair methods are known using the method of cementing, lowering a casing string of smaller diameter followed by its cementing P.

However, these methods are expensive and time consuming. Cementing brings success only in 40 and short-lived, and the launch of a smaller diameter casing reduces the flow rate and complicates subsequent repair work.

There is a known method for repairing casing strings, including the release into the well of a patch of a length longer than the damage interval of the casing, its expansion and pressing against the casing by creating radial loads. In order to ensure complete tightness of the repaired area, a sealing layer is applied to the outer surface of the workpiece.

The technology for this method is as follows.

A blank patch is installed on the device to expand it and descend into the well at a predetermined interval. During the descent process, the expander

10. has a diameter corresponding to its free breathing in the column (.transport). Upon reaching a predetermined depth, the expander is pushed up to such a diameter that, in the process of pulling it through the workpiece patch, create the radial loads necessary to expand the workpiece patch to create a stress state of the patch with a column. The rider extends with constant radial loads through a pre-fabricated patch, which, having taken a circular shape and having received a stress state

3909

in the casing, turns into a plaster. The expander device then rises from well 2.

The disadvantage of this method is the creation of a stressed state of a patch with a column along its entire length, which, in the case of damage in the form of perforations, cracks, wear and corrosion, leads to additional damage to the casing or to an increase in the old ones (Fig. 1).

The purpose of the invention is to reduce the stresses arising in the casing body in the damage interval.

This goal is achieved by having a patch above and. below the casing damage interval, the radial loads are larger than the radial loads on the patch corresponding to the casing damage interval.

The method is implemented as follows.

A blank of a patch longer than the damage interval is lowered with a device for extending it into a predetermined interval of the casing so that the center of the blank patch falls against the middle of the damage interval. The device is pressurized to drive the spreader, which is required to generate radial forces in order to obtain a stressful patch-string system. Pull the spreader through the workpiece patch, not dosing it before the start of the damage interval. Relieve the pressure in the expander in order to reduce the radial forces transmitted by the patch to the casing.

The expander without pressure is pulled through the blank by a patch for a length slightly longer than the damage interval, in order to ensure the passage of the column, but without a stress state in this area.

Again, the pressure in the expander is necessary to create for the sake of | 4

for the purpose of a half-body tensioned band-column system and pulling the expander through the rest of the workpiece patch. If necessary, press the plaster to the column with the next passages of the expander to pass a damage interval without pressure. The forces transmitted by the expander along the length of the plaster can be represented by a known method by the graph shown in FIG. 2, and as proposed in FIG. 3. On the graph there are radial forces of the patch transmitted to the casing; L, is the length of the casing section where the patch is applied; Zone I - an intact area, Zone II - a damaged area.

formula of invention

A method for repairing casing strings, including the release into the well of a patch of length longer than the damage interval of the casing string, its expansion and pressing against the casing string by creating radial loads, which are based on the fact that, in order to reduce the stresses arising in the casing body in the interval damage): {for the patch above and below the damage interval of the casing create radial loads greater than the radial loads on the patch corresponding to the damage interval of the casing.

Sources of information taken into account during the examination

1.Sidorov I.L. Restoration of casing tightness in oil and gas wells. Thematic scientific and technical reviews. Ser. Drilling, M., VNIIOENG, 1972, p. 78-89

2. High-quality repair liner. Journal of Petroleum Technology. 1962, V. U, r 17., (prototype).

Pith

b

H

2 fPuiJ

(put. I

fl

/

FIG. .3

Claims (1)

Claim The method of repairing casing strings, including the descent into the well of a plaster with a length longer than the damage interval of the casing string, its expansion and pressing against the casing string by creating radial loads, in order to reduce stresses in the casing body in the damage interval On the patch above the interval of damage to the casing, radial loads are greater than the radial loads on the patch, corresponding to the interval of damage to the casing.