GB2173839A - Long range borehole drilling equipment - Google Patents

Abstract

A releasable plug (7) sealably engageable inside hollow members (1, 3) of a drill string comprises an annular seal (20) which is resiliently biassed by the action of a spring (16) to sealably engage the inside of the hollow member and which is released from its sealed mode by the action of pressurised fluid in working chamber (24). The plug can be moved from a position (indicated by reference number 7) in which it does not obstruct flow of drilling fluid along the drill string to a position (indicated by reference number 7') in which it seals the drill string to prevent leakage of drilling fluid when the drill string is being extended. <IMAGE>

Description

SPECIFICATION Long range borehole drilling equipment This invention relates to long range borehole drilling equipment.

In particular, but not exclusively, the invention relates to equipment for use when drilling substantially horizontal or upwardly inclined or upwardly directed boreholes in rock or mineral strata, hydraulic fluid being pumped along the string of hollow drill rods towards a boring bit mounted on the leading end of the drill string.

At present such a drilling technique suffers from the disadvantage that every time a new drill rod has to be added to extend the advancing drill string it is necessary to allow the hydraulic fluid to drain from the drill string.

Not only does such a technique waste time waiting for the fluid drain out of the drill string but also the excess of fluid at the drilling station tends to produce poor operational conditions. Also, the fluid drained away may be wasted.

An object of the present invention is to provide improved drilling equipment which tends to overcome or reduce the above mentioned problems.

Accordingly, the present invention provides a releasable plug sealably engageable inside hollow members of a drill string, the plug comprising a body component having inlet means for pressurised fluid and a slide component slideably mounted with respect to the body component such that the two components form a piston and cylinder arrangement movable in one direction under the action of a resilient bias acting between the two components and movable in the opposite direction against the resilient bias by pressurised fluid fed to the inlet means, the plug having an outwardly directed, open trough for accommodating annular seal means, the trough having opposed sides constituted by portions of the two components, respectively, such that movement of the piston and cylinder arrangement in said one direction reduces the trough width thereby squeezing and radially expanding the annular seal means such that, in use, when the plug is located inside a hollow drill string member, the plug is urged into a sealably engaged mode plugging the inside of the member, while movement of the piston and cylinder arrangement in said opposed direction tends to increase the trough width thereby reducing the squeezing action on the annular seal means such that, in use, the plug is released from its sealably engaged mode and is movable along the hollow drill string member.

Preferably, the inlet means provided on the body component is adapted to receive a detachable hydraulic fluid supply line.

Conveniently, the body component is adapted to receive electrical connector means and is provided with electrically conductive means for transmitting electrical signals through the body component.

Preferably, the electrical connector means comprises a first electrical connector on a leading portion of the body component which, in use, is directed towards the boring bit end of the drill string, and a second body component on a trailing portion of the body component, the electrically conductive means extending between the two electrical connectors.

The present invention also provided drilling equipment comprising a plug as defined above.

By way of example, one embodiment of the present invention will be described with reference to the accompanying drawings, in which: Figure 1 shows a plug according to the present invention mounted inside one embodiment of a drill string (only one end portion of which is shown), for the sake of explanation the plug is shown in two alternative positions; and Figure 2 shows the plug mounted inside a second embodiment of a drill string (again only one end portion of which is shown).

Figure 1 shows one end of a drill string for drilling a long range borehole in rock or mineral strata, the illustrated end being that remote from the boring or drilling bit and adjacent to the drilling machine (not shown). Although not shown in detail the embodiment of drill string shown in Figure 1 is of the kind comprising a down the hole motor such that only the part of the drill string adjacent to the boring or drilling bit is rotated.

Figure 1 shows one end of a non-rotary drill rod 1 fixedly connected to an adaptor piece 2 sealably engaged in an end section 3. The adaptor piece is capable of limited rotation relative to the end section and bearings 4 are provided in the connection assembly as well as a seal 5. The end section is provided with an inlet 6 for receiving a pressurised hydraulic fluid supply line (not shown). The end section also defines a branch 8 for receiving a plug 7 during normal drilling operations. The plug also is showm in an alternative position (denoted by 7') in which it provides a fluid tight seal along the drill rod 1. The function of the two operational positions will be made clear later in this specification.

The plug comprises a generally cylindrical elongate body component 10 adapted to slidably engage in a sealed passage 11 provided in the branch of the end section. The leading portion of the body component ie that directed towards the drilling bit is provided with a flange 12 which defines one side 13 of an outwardly directly open trough 14. The base and the other opposed side 9 of the trough are defined by a slide component 15 slideably mounted along the body component. The slide component is slidable along the body component in one direction under the action of a resilient bias provided by a spring 16 engaged between the slide component and an abutment shoulder 17 retained in position by a large nut 18 screwed on to a thread 19 provided on the body component.Movement of the slide component in said one direction under the action of the resilient bias reduces the effective width of the trough thereby squeezing and radially expanding annular seal means constituted by a number of seal rings 20. The expanded seal rings sealably engage the adjacent inside wall of the end section or of the drill rod as will be explained later in the specification.

The slide component 15 if urged to slide along the body component in an opposed direction to said one direction under the action of pressurised hydraulic fluid supplied to inlet means 21 provided on a trailing portion of the body component and fed along passages 22 and 23 to a sealed working chamber 24 defined between the body and slide components such that the two components form a hydraulic piston and cylinder arrangement. Movement of the slide component in said opposed direction overrides the action of the resilient bias and effectively increases the width of the trough thereby reducing the squeezing action of the seal means and releasing the plug from its sealably engaged mode.

The inlet means 21 constitutes a dual electrical or hydraulic connector. As shown on plug 7 in Figure 1 the inlet means constitutes an electrical socket for a removable electrical connector 25 provided on one end of an electrical cable 26. The electrical connector 25 is engageable with an electrically conductive lead 27 extending along the aforementioned passage 22 provided in the body component and electrically connected to a further electrical connector 28 which in turn is electrically connected to a cable 29 extending along the drill string to sensor or control means (not shown) located adjacent to the drilling bit.

The inlet means 21 also constitutes a hydraulic inlet port for a removable hydraulic connector 30 shown connected to the plug 7' sited along the drill rod 1 in Figure 1. The hydraulic connector 30 is fixedly mounted on one end of a rigid pipe 31 extendable through the aforementioned passage 11 and providing means for moving the plug in a released mode along the drill string between the two positions shown in Figure 1. It should be noted that the electrical and hydraulic connections are alternative connections to the inlet means.

In normal drilling operations, the plug 7 is located in the branch 8 of the end section where it does not obstruct the flow of pressurised hydraulic fluid supplied to inlet 6 and passing along the drill string to lubricate the drilling or boring bit and to rinse away fine particular material cut by the bit. During drilling operations signals are transmitted from the sensor monitoring means sited adjacent to the bit along cable 29 and lead 27 and along cable 26 via electrical connector 25 which is engaged in the inlet means 21. During this period the action of the resilient bias is to urge the slide component 15 in said one direction to squeeze the seal rings 15. The plug is in its engaged seal mode.

Upon the drill string being advanced a drill rod length it is necessary to halt drilling and install a further drill rod in the string. This is achieved by disconnecting the electrical connector 25 from the inlet means 21 and replacing it with the hydraulic connector 30 mounted on the rigid pipe 31. Pressurised hydraulic fluid then is applied to the working chamber 24 urging the slide component 15 to move in said opposed direction to reduce the squeezing action on the seal rings to release the plug from its engaged sealed mode. Then with the hydraulic supply still closing inlet passage 6 the plug is advanced along the inside of the drill string into the position indicated by reference number 7' in Figure 1.The hydraulic supply then is switched off allowing the slide component to move in said one direction to squeeze and radially expand the seal rings which thereby sealably engage the inside of the drill rod 1, the plug being in its engaged sealed mode tending to retain hydraulic fluid inside the drill string.

The hydraulic connector then is detached from the inlet means 21 and with=drawn via the open passage 11. The adaptor piece 2 is disconnected from the drill rod 1 and a further drill rod added to the drill string. The adaptor piece is reconnected on to the end of the drill string on to the newly added drill rod. An extended pipe 31 provided with hydraulic connector 30 is reinserted via passage 11 and fed along the inside of the newly added drill rod to re-engage the inlet means 21. Pressure fluid is re-introduced to the chamber 24 via hydraulic connector 30 and the slide component urged in said opposed direction to release the plug from its engaged sealed mode.

The plug then is retracted from its advanced position 7' back to its withdraw position 7 located in the branch 8 of the end section 3.

The hydraulic fluid connector 30 is removed from the plug which thereby takes up its engaged sealed mode and the electrical connector 25 is re-connected to the inlet means.

Normal drilling now can proceed. It will be appreciated that the present invention provides equipment enabling hydraulic fluid to be retained in the drill string during the period when the drill string is extended. The plug is particularly useful for horizontal boreholes or upwardly inclined or upwardly directed boreholes.

Figure 2 shows the same plug 7 installed in a different embodiment of drilling equipment to that shown in Figure 1. The plug and its operation are substantially the same as described previously with reference to Figure 1 and no further description of the plug is in cluded.

In Figure 2 the drill string comprises a rotary drill rod assembly in which the drill rods are rotated with the drilling or boring bit (not shown) the drill rods being rotated by a drilling machine (not shown) drivably engaging the drill rods.

As seen in Figure 2 the plug in its withdrawn position is sealably engaged on the inside of adaptor piece 202 which rotates with the drill rods. Thus, the plug rotates with the drill rods and the cable 29 is not subjected to any twisting action. When the drill string is being extended the plug is advanced along the inside of the drill string to be sealably engaged in the end of the last installed drill rod 201. The drill string then is extended as previously described with reference to Figure 1.

In other embodiments of the invention the slide component is urged in the opposed direction to said one direction under the action of pneumatic or compressed gas means.

Claims (6)

1. A releasable plug sealably engageable inside hollow members of a drill string, the plug comprising a body component having inlet means for pressurised fluid and a slide component slideably mounted with respect to the body component such that the two components form a piston and cylinder arrangement movable in one direction under the action of a resilient bias acting between the two components and movable in the opposite direction against the resilient bias by pressurised fluid fed to the inlet means, the plug having an outwardly directed, open trough for accommodating annular seal means, the trough having opposed sides constituted by portions of the two components, respectively, such that movement of the piston and cylinder arrangement in said one direction reduces the trough width thereby squeezing and radially expanding the annular seal means such that, in use, when the plug is located inside a hollow drill string member, the plug is urged into a sealably engaged mode plugging the inside of the member, while movement of the piston and cylinder arrangement in said opposed direction tends to increase the trough width thereby reducing the squeezing action on the annular seal means such that, in use, the plug is released from its sealably engaged mode and is movable along the hollow drill string member.

2. A plug according to claim 1, in which the inlet means provided on the body component is adapted to receive a detachable hydraulic fluid supply line.

3. A plug according to claim 1 or 2, in which the body component is adapted to receive electrical connector means and is provided with electrically conductive means for transmitting electrical signals through the body component.

4. A plug according to claim 3, in which the electrical connector means comprises a first electrical connector on a leading portion of the body component which, in use, is directed towards the boring bit end of the drill string, and a second body component on a trailing portion of the body component, the electrically conductive means extending between the two electrical connectors.

5. A releasable plug substantially as described herein and substantially as shown in the accompanying drawings.

6. Drilling equipment comprising a plug, as claimed in any one of the preceding claims.