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Releasable mill

a releasable mill and milling machine technology, applied in the direction of drilling casings, drilling pipes, borehole/well accessories, etc., can solve the problems of time-consuming and expensive process of tripping a work string into or out of a well, and the passageways are not large enough to provide the desired degree of access to the lower formation

Inactive Publication Date: 2007-09-27
BAKER HUGHES INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is a mill assembly with a releasable milling head attached to a mill body using shear pins or another releasable fastening feature. The mill assembly can be lowered into a bore hole to mill out a plug, and then the milling head can be released from the work string and allowed to drop into the bore hole. This separation of the milling head from the mill body leaves a substantially open bore into and through the work string, allowing production from the lower formation to take place through this open bore. The milling head has a check valve to prevent the uphole flow of fluids during a kick or pressure excursion. The invention provides a novel solution for milling out plugs in bore holes.

Problems solved by technology

This is because, although the mill may have passageways for drilling fluid, these fluid passageways are not sufficiently large to provide the desired degree of access to the lower formation.
As is well known, tripping a work string into or out of a well is a time consuming, expensive process.

Method used

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Examples

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second embodiment

[0030] the milling head is shown in FIG. 6. This embodiment of the milling head 140 can be fitted with a check valve comprising a ball seat 142, a check ball 144, and a spring 146. It can be seen that, as milling fluid passes downhole through the fluid path in the milling head 140, the check ball 144 can be lifted off its seat 142, against the bias of the spring 146, to allow flow out the lower end of the work string. A kick or pressure excursion sometimes occurs in the formation fluids, which could create an undesirable flow in the uphole direction through the work string. To prevent this, the spring 146 biases the check ball 144 toward engagement with its seat 142. As pressure below the milling head 140 increases above the drilling fluid pressure, this causes the check ball 144 to seat more securely, thereby preventing flow in the uphole direction.

third embodiment

[0031] the apparatus 210 of the present invention is shown in FIGS. 7 and 8. In this embodiment, the mill body 212 is secured to the milling head 214 by shear pins 216 in shear pin bores 224 and 226 in the mill body 212 and the milling head 214, respectively. Flow passages 228 are provided through the milling head 214. However, in this embodiment, the check valve comprises a swing check type valve, with a check valve body 262 assembled in the milling head 214, and with a flapper valve 264, which is pivotably mounted to the check valve body 262 by a pivot pin 266. The check valve body 262 can be retained in the milling head 214 by one or more snap rings or pins, as is known in the art. The flapper valve 264 is biased toward the closed position by a spring. Flow of fluid down through the apparatus can open the flapper valve 264 against the spring bias, but backflow through the check valve is prevented by shutting of the flapper valve 264, which seats against the lower side of the chec...

first embodiment

[0032] Also provided in this embodiment is a fishing neck 260, which is retained in the milling head 214, above the check valve body 262, by one or more snap rings or pins, as is known in the art. A ball seat 230 is provided in the upper side of the check valve body 262. When milling has been completed, and it is desired to release the milling head 214 from the mill body 212, a ball 222 is pumped downhole through the work string, to seat in the ball seat 230. Increasing pressure above the pumpable ball 222 then shears the shear pins 216, releasing the milling head 214 from the mill body 212, as in the If it is desired to subsequently remove the milling head 214 from the well bore, known fishing techniques can be used to attach to the fishing neck 260 and pull the milling head 214.

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PUM

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Abstract

A mill assembly having a milling head which is releasable from the mill body, such as by shearing a shear pin. The release mechanism can be released by dropping a pumpable plug through the work string to block fluid flow through the releasable milling head, or by increasing fluid flow through a constriction in the releasable milling head to increase the back pressure above the milling head. A check valve in the milling head can prevent uphole flow through the work string in the event of a pressure excursion. A fishing neck can be attached to the milling head.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of co-pending U. S. patent application Ser. No. 10 / 916,773, filed Aug. 11, 2004, for “Releasable Mill”, which claims the benefit of U. S. Provisional Patent Application No. 60 / 495,021, filed Aug. 13, 2003, for “Releasable Bridge Plug Mill”.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] This invention is in the field of apparatus used to mill out downhole equipment in a well, such as in an oil or gas well. [0005] 2. Background Art [0006] Some oil or gas wells are drilled into locations at which multiple oil or gas formations are found, at different depths. That is, one hydrocarbon formation may be above or below another, and there may be more than two such formations at different depths. It is common to produce hydrocarbons from only one selected formation at a time. One means used to assist in thi...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): E21B17/00E21B10/60E21B10/62E21B21/10
CPCE21B10/60E21B21/10E21B10/62
Inventor DEGEARE, JOSEPH P.PLANTE, MARKDOLYNIUK, DAVID A.DAVIS, JOHN P.
Owner BAKER HUGHES INC
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