RU2298082C1 - Downhole fishing tool - Google Patents

Abstract

FIELD: oil and gas industry, particularly fishing for or freeing objects in boreholes or wells, namely for removing damaged strings from cavernous wells.

SUBSTANCE: fishing tool comprises body with axial channel and stepped outer surface, through bell and milling crown fixedly connected to the body, guiding means with end slot for damaged pipe string receiving connected to the body by means of shear member and damaged string centrator arranged in milling crown interior. The guiding means is provided with fixing unit to retain the guiding means with respect to well wall. Minimal inner centrator diameter is less than inner diameter of lower through bell end. Fixing unit of guiding means is made as barrel-type rollers grouped in several rows. Each barrel-type roller may rotate about horizontal pin secured in openings formed in side surface of guiding means. Rollers have curvature radius in plane view of not less than well diameter in area of damaged string head location.

EFFECT: increased reliability and efficiency, decreased time of fishing work performing.

3 cl, 2 dwg

Description

The invention relates to mining, and in particular to devices for extracting a pipe string, the "head" of which is in the well cavity.

Known downhole catcher containing a housing with a pivotally attached hook and a passage bell (see USSR copyright certificate No. 141833, class E 21 B 31/02, 1961).

The disadvantage of this catcher is the low efficiency of its operation, associated with the need to use a hydraulic drive and the difficulty of creating the necessary torque to rotate the outlet hook to capture a dangling pipe string, the head of which is located in the cavity.

The closest in technical essence and the achieved result is a downhole catcher, which includes a housing with an axial channel and a stepped outer surface, a passage bell and a milling crown rigidly connected to it, and a guide with an end groove under the emergency pipe string, connected to the body via a shear element ( see the rationale “Device for eliminating the breakage of a drill pipe deflected into the cavity” in the “Collection of rationalization proposals and inventions recommended for implementation in ge the biological industry ", issue 8 (152), M., VIEMS, 1983).

The disadvantage of this catcher is its low reliability due to the lack of rigid fixation of the guide, and therefore the emergency string relative to the walls of the well. The absence of such a fixation creates significant difficulties when milling an emergency column and leads to a quick failure of the milling crown. Another disadvantage of the known catcher is the difficulty of "covering" the cut-off "head" of the emergency column with a passage bell due to the lack of a centralizer for the emergency column in the cavity of the milling crown. Considering that the “head” of the emergency column after its milling is constantly pressed to the walls of the milling crown in the known catcher, the connection of the emergency column with the bell requires considerable time.

In connection with the stated technical objective of the invention is to increase the reliability and efficiency of the catcher due to the rigid fixation of the emergency column relative to the walls of the well and its center relative to the passage bell.

The problem is solved in that in the downhole catcher, comprising a housing with an axial channel and with a stepped outer surface, a passage bell and a milling crown are rigidly connected to it and a guide with an end groove under the emergency pipe string connected to the housing by means of a shear element, according to the invention it is equipped with a guide fixation unit relative to the walls of the well and a centralizer for the emergency column, located in the cavity of the annular milling cutter, and the minimum centralizer inner diameter is less the inner diameter of the passage bell on the lower end.

The solution of the task is also facilitated by the fact that:

- the guide fixing unit is made in the form of barrel-shaped rollers, each of which is mounted for rotation around a horizontal axis fixed in windows made on the side surface of the guide, and the radius of rounding of the rollers in terms of at least the diameter of the borehole in the area of the head of the emergency string;

- barrel-shaped rollers are located in several tiers.

The invention is illustrated in the drawing, in which figure 1 is a General view of the proposed catcher in longitudinal section; figure 2 is a section aa in figure 1. The downhole catcher comprises a housing 1 with an axial channel 2 and a stepped outer surface, a passage bell 3 and a milling crown 4, rigidly connected to the housing 1 by means of a threaded sleeve 15, and a guide 5 connected to the housing 1 by means of a shear pin 6. A variant of connecting the guide 5 with the housing 1 through the intermediate sleeve 7, which simplifies the manufacturing technology of the catcher and reduces its metal consumption by reducing waste. The guide 5 is made with a side slot 8 under the emergency column 9, and the end sections of the side surface and the guide 5 forming the slot 8 are made with curves 16 to facilitate the entry of the emergency column into the slot 8. The guide 5 is equipped with a fixing unit made in the form of several tiers of barrel-shaped rollers 10. Each of the rollers 10 is mounted to rotate around a horizontal axis 11, mounted in windows 12, made on the side surface of the guide 5. Moreover, the radius of curvature of the rollers 10 is not m it borehole diameter "head" location area emergency column 9. Location of rollers 10 in multiple tiers increases the accuracy of centering the guide 5 and thus shortens the time required for the elimination of the accident with the pipes. To increase the reliability of capture of the emergency column, the catcher is equipped with a centralizer 13 with a conical inner surface rigidly connected to the milling crown 4 by any known method, for example, pins 14 and located directly under the lower end of the passage bell 3. In this case, the minimum inner diameter of the centralizer 13 is smaller than the inner diameter of the passage bell 3 at the bottom.

Downhole catcher works as follows. The proposed catcher is recommended to be used in wells prone to collapse and having caverns, where, as a rule, the "head" of the emergency string 9 deviates. The catcher is connected to the drill string (not proven) by thread 17 and lowered into the well in the "head" location emergency string 9. In this case, the guide 5 is oriented so as to align its slot 8 with the emergency string 9. After that, the catcher is lowered down and thanks to the wedge-shaped shape of the slot 8, the guide 5 rigidly fixes the drill string 9 relative to the walls of the well. By creating excessive force on the drill string, the pins 6 are cut and the milling crown 4 is lowered down to the contact with the emergency string 9. Then, rotating the drill string, the milling crown 4 cut the emergency string 9, the “head” of which is fed into the cavity of the centralizer 13 and then into the cavity passage bell 3. In this case, due to the close proximity of the ends of the passage bell 3 and centralizer 13 facing one another and the passage of the passage of the centralizer 13 with a diameter greater than the diameter of the passage of the bell 3 at the lower end, the emergency string 9 is guaranteed to fall into the cavity of the bell 3 and is captured by it when the drill string is rotated together with the bell 3. The captured string rises to the surface along with the guide 5, which is held on the stepped surface of the housing 1. After raising the catcher to the surface, disconnect the emergency string 9, replace shear pin 6 and the catcher is ready for a new descent.

The use of the proposed catcher in comparison with the prototype can significantly reduce the time required to eliminate accidents with a drill string, the "head" of which is located in the cavity. This is achieved by improving the conditions for milling the emergency column with a milling crown and aligning the emergency column before being fed to the through-bell.

Claims (3)

1. A downhole catcher comprising a housing with an axial channel and a stepped outer surface, a passage bell and a milling crown and a guide with an end groove for an emergency pipe string connected to the housing by a shear element, rigidly connected to it, characterized in that it is equipped with a fixing unit guide relative to the walls of the borehole and a centralizer for the emergency column, placed in the cavity of the milling crown, and the minimum inner diameter of the centralizer is less than the inner diameter of the passage bell la on the bottom. 2. The downhole catcher according to claim 1, characterized in that the guide fixing unit is made in the form of barrel-shaped rollers, each of which is mounted to rotate around a horizontal axis fixed in windows made on the side surface of the guide, and the rounding radius of the rollers is not less than the diameter of the well in the area of the "head" of the emergency string. 3. Downhole catcher according to claim 2, characterized in that the barrel-shaped rollers are located in several tiers.

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