GB2207158A

GB2207158A - Drilling or coring tool

Info

Publication number: GB2207158A
Application number: GB08812873A
Authority: GB
Inventors: Cyril Perrett
Original assignee: Smit & Sons Diamond Tools
Current assignee: Smit & Sons Diamond Tools
Priority date: 1987-06-11
Filing date: 1988-05-31
Publication date: 1989-01-25
Also published as: GB8812873D0

Abstract

A drilling tool or coring tool particularly for uncapping an oil well sealed by a packer or plug includes a body portion 17 with a coned end 18 formed with a thread 19 for attachment to a stabilizer unit. The drill bit has a lower portion 20 with a bore 21 in it into which is welded a screwed or otherwise fixed pilot drill 22 adapted to drill a four inch diameter pilot hole. To this drill is fitted a core-catcher 47. The drill bit has radial arms 25 (26) 27 and (28) which are formed without any diamonds or other cutters on their outside edges. In a second embodiment (not shown) the coring tool includes a pilot drill bit mounted on a shaft extending along the axis of a core cutter which has no diamonds mounted on its outer surface. <IMAGE>

Description

DRILLING OR CORING TOOL This invention relates to a drilling or coring tool.

The invention has particular, but not exclusive, application in the uncapping of sealed oil well holes.

Oil well holes are sealed by use of a bung or packer which may comprise for example a layer of aluminium followed by a layer of rubber, followed by a further layer of aluminium. Other configurations and other materials are used including various metallic and resilient constituents.

An object of the invention is to provide a drilling or coring tool which is capable of drilling through and clearing or cutting a core through both the metallic and resilient constituents of the bung.

In accordance with the present invention a drilling or coring tool is provided, particularly for uncapping sealed oil wells, the tool comprising a composite drilling bit adapted to drill a small guide hole followed by a larger hole of the full diameter of the casing of the sealed well hole, or to drill and remove a core of a diameter less than that of the casing, the bit having no diamonds or cutters on its outer surfaces which may come into contact with the oil well casing wall.

Preferably the drilling tool is used in combination with a stabilizer to which it may be attached, the stabilizer having radially extending ''wings" or "pads" with wear resistant surfaces adapted to contact the casing walls and to provide stabilization of the drill bit during drilling of the bung.

Preferably the drilling tool has radial drilling cutters which extena the full required diameter of the casing. Alternatively a coring cutter may be used so as to cut and remove a core of the bung or packer.

If the drilling tool is a core cutter it is preferably cylindrical and has within it a drill shaft which carries the pilot drill bit, a centralizing plate being slidable on the shaft and within the core cutter.

The centralizing plate, which keeps the drill shaft running true, can slide up the shaft being pushed by the core as it is being drilled.

Preferably a core retaining ring is provided on the pilot drill bit shaft and also a core catcher may be provided on the internal surface of the coring tool or bit to retain and remove the core of the bung or packer. A core catcher may be provided to retain and remove the core of the bung or packer.

The pilot drill may be any conventional form of drill and may be attached to the body of the tool below the radial cutters.

The tool may have a tapered thread at one end for attachment to the stabilizer unit and the stabilizer may have a correspondingly tapered internally threaded conea surface.

In the accompanying drawings: Figure 1 illustrates, in section, a well casing which has been capped by a bung or packer; Figure 2 is a longitudinal section through a tool embodying the present invention; Figure 3 is an underneath view of the same tool; Figure 4 is a longitudinal section through a stabilizer unit for use with the invention; Figure 5 is a plan view of the stabilizer unit; Figure 6 is a section through a drilling or coring tool forming a second embodiment of the present invention.

In Figure 1 is shown a well hole 10 which is surrounded by conventional well hole casing 11, shown diagrammatically. The oil well hole is sealed by means of a bung 12 which has an aluminium layer 13 a rubber layer 14 and an aluminium cone or "bomb" 15 with a seal at 16.

In order to uncap the oil well it is necessary to drill through the bung and remove it. Conventionally this is done by sending a roller-cone bit down the hole, but difficulties are experienced in drilling through the rubber layer 14.

The drill bit in accordance with the invention shown in Figures 2 and 3 comprises a body portion 17 with a coned end 18 formed with a thread 19 for attachment to a stabilizer unit (shown in Figures 4 and 5). The drill bit has a lower portion 20 with a bore 21 in it, into which is welded a screwed or otherwise fixed pilot drill 22 adapted to drill a four inch diameter pilot hole. To this drill is fitted a core-catcher 47.

The drill bit has radial drill arms 25,26,27 and 28 which are formed without any diamonds or other cutters on their outside surfaces 29, 30, 31 and 32. Each of these radial drill arms has a cutting edge 33, 34, 35 and 36 respectively.

The radial arms may extend to a diameter of say 171/2 inches, assuming that a 171/2 inch diameter casing is employed.

The drill bit is stabilized by means of a stabilizer shown in Figures 4 and 5 consisting of a body 36 with radial fins 37,3S,39 and 40, each radial fin having a wear resistant curved outer surface 41,42,43 and 44 respectively.

At its lower end the stabilizer has an extension 45 with an internally threaded coned surface 46 to enable the drill bit to be attached to the stabilizer.

The stabilizer wear resistant surfaces will contact the drill casing and stabilize the bit during drilling without causing wear or marking on the drill casing.

It will be appreciated that there are no cutters or diamonds on the outside diameter of either the drill bit or the stabilizer and so no damage will be done to the oil well casing.

The wings 37,38,39 and 40 of the stabilizer are long-itudinally tapered by one degree to prevent debris from clogging up as the drilling operation is in progress.

by use of this drill bit it is possible to drill safely both through the aluminium and rubber of the bung and thus to remove the bung completely without damaging the oil well casing.

Once shear pins are fractured, the core catcher 47 on the pilot drill will prevent the remainder of the packer from falling down the well hole.

In Figure 6 of the drawings the tool 110 comprises a pilot drill 111 attached to a pilot drill shaft 117 which is screwed onto a back plate 119. behind the pilot drill 111 is an internal core catcher 112 and a retaining ring 113 adapted to catch the core to prevent it from dropping down the oil well hole.

An aluminium centralizing plate 116 is fitted onto the shaft 117 to keep the shaft running true. The plate 116 can slide up and down the shaft and may be pushed up the shaft by the core as it is being drilled.

The tool includes a coring bit having a coring bit crown 114 which has diamonds or other cutting media on the face 114A and internal diameter 114B only. Thus there are no diamonds or other cutting media on the face 114C which may come into contact with the oil well casing wall.

The diameter of the coring bit crown 114 and of its supporting coring barrel 120 may be chosen to suit the particular diameter of the oil well hole to be uncapped.

Inside the coring barrel 120 is an annular core catcher 115. The barrel 120 is screwed onto a back plate 119 so that the barrel may be removed to extract the core. The back plate 119 has holes 121 and 122 drilled through it, so that, optionally, internal flushing may be used.

Back plate 119 is welded onto a tapered threaded connection 118 which has a bore 123 connecting to the holes 121 and 122.

The complete unit is preferably used in conjunction with a stabilizing unit described in our co-pending application, mentioned above. This stabilizes the drill bit during drilling.

By using the tool shown in Figure 6, which cuts and extracts a core, a number of advantages result: 1. This is a cheaper method of drilling than with the full hole drilling.

2. brilling is achieved more quickly.

3. The method is safer because the full core is captured.

Claims

CLAIhS:-

1. A drilling or a coring tool, particularly for uncapping sealed oil wells, the tool comprising a composite drilling bit adapted to drill successively a small guide hole followed by a larger hole of the full diameter of the casing of the sealed well hole, or adapted to drill a small guide hole and then to remove a core of a diameter less than that of the casing, the bit having no diamonds or cutters on its outer surfaces which may come into contact with the oil well or the casing walls.

2. A drilling or a coring tool according to claim 1 in combination with a stabilizer to which it is attached, the stabilizer having radially extending "wings" or "pads" with wear resistant surfaces adapted to contact the casing walls and to provide stabilization of the drill bit during drilling of the bung.

3. A drilling tool according to claim 1 or claim 2 which has radial drilling cutters which extend the full required diameter of the casing.

4. A coring cutter according to claim 1 or claim 2 adapted to cut and remove a core of the bung or packer.

5. A coring cutter according to claim 4 which is cylindrical and has within it a drill shaft which carries the pilot drill bit, a centralizing plate being slidable on the shaft and within the core cutter.

6. A core cutter according to claim 5 and in which the centralizing plate, which keeps the drill shaft running true, can slide up the shaft being pushed by the core as it is being drilled.

7. A coring cutter according to any of claims 4 to 6 and in which a core retaining ring is provided on the pilot drill bit shaft.

8. A coring cutter according to any of claims 4 to 7 and in which a core catcher is provided on the inernal surface of the coring tool or bit.

9. A drilling tool substantially as hereinbefore particularly described and as illustrated with reference to Figures 1 to 5 of the accompanying drawings.

10. A coring tool substantially as hereinbefore particularly described and as illustrated in Figure 6 of the accompanying drawings.