GB2135714A - Mobile drilling rig - Google Patents

Abstract

The drilling rig, which is particularly suited for use in developing countries, has a support structure, e.g. a chassis (10), and a mast which is pivoted to the chassis so that it can be lowered during transportation. An elongate drive member (27) is supported by a wire (25) which is connected over a sheave (30) to a winch (28.) A drilling device e.g. a drill bit or auger can be attached to the drive member (27). A rotary drive device (32) for rotating the elongate drive member is to all intents and purposes permanently mounted on the elongate drive member. When a drilling operation is to be performed, the rotary drive device can be releasably coupled to the drive shaft therefor and releasably fastened to the chassis. However, it can be uncoupled and unfastened readily in order that it can be swung as one unit with the elongate drive member away from the centre line of a hole being drilled in order to remove spoil from an auger attached to the elongate drive member or to allow a casing to be lowered into the hole. <IMAGE>

Description

SPECIFICATION Mobile drilling rig This invention relates two a mobile drilling rig, particularly but not exclusively for mineral exploration, soil investigation and drilling to make water wells.

Known mobile drilling rigs include a mast mounted on a support structure, a winch for raising and lowering the drilling members, and a power drive for rotating the drilling members. The power drive takes one of two forms. In thefirstformthe power drive comprises a rotary head mounted on a carriage slidable along the mast and a hydraulic motoralso mounted on the carriage for driving the rotary head.

Rigs provided with such a power drive require the provision of an hydraulic pumptooperatethe motor and an hydraulic control circuit and are, inevitably, expensive in terms of both capital equipment and maintenance. In the second form the power drive comprises a rotary drive device carried bythe support structure atthefootofthe mast. The rotary drive device rotates an elongate drive member which is connected to thewinch by a wire passing overa sheave atthetop ofthe mast. During a drilling operation, the elongate driver member is vertically slidable through the rotary drive device whilst being driven in rotation bythe latter.When drilling large diameter holes in soft strata, instead of using a drill bit in combination with a system for circulating mud or air through the hole to remove spoil, it is common practice to use an auger. priodically, the spoil has to be removed from the auger and, when using a rig with the above mentioned second form of power drive, the following steps have to be carried out in orderto accomplish this: (a) the elongate drive member is raised by the winch until the coupling between the elongate drive member and auger is accessible (b) the coupling is disconnected after supporting the auger.

(c) the elongate drive member is raised furtherto liftthe latter out ofthe rotary drive device (d) the rotary drive device is swung out oftheway (e) thewinch is lowered for connection to the auger (f) the auger is raised by the winch and swung away from the centre line ofthe hole, whereupon the spoil can be removed from the auger by banging or shaking (g) steps (a) - (f) are performed in reverse order to reposition the auger in the hole.

This procedure is both complicated and time consuming.

According to the invention, there is provided a mobile drilling rig comprising a support structure, a mast pivotably mounted on the supportstructure for movement between a raised rig operating position and a lowered transportable position, a winch mounted on the support structure, a rotatable elongate drive memberfor supporting a drilling device and being suspended from the mast by a flexible elongate element connected to the winch, a rotary drive device for rotating the elongate drive member about the longitudinal axis of the elongate drive member, meansfor driving the winch. meansfor driving the rotary drive device, and means for releasably coupling the rotary drive device to its drive means, the rotary drive device being mounted about the elongate drive member so that when a drilling operation isto be performed and the rotary drive device is coupled to its drive means the elongate drive means is rotated by the rotary drive device whilst being able to move vertically or substantially vertically therethrough and the rotary drive device being carried bythe elongate drive memberso that it can be uncoupled from its drive means and swung as one unitwith the elongate drive member awayfrom the centre tine of a hole being drilled.

When a drilling rig according to the invention is used with an auger, in order to remove spoil from the auger onlythe following steps have to be carried out: (a) the elongated drive member and auger are raised by the winch to remove the augerfrom the hole and to supportthe rotary drive member ready for uncoupling (b) the rotary drive member is uncoupled and the elongate drive member, rotary drive member and auger are then swung to one side, where the spoil can be removed from the auger by banging or shaking (c) steps (a) and (b) are performed in reverse order to reposition the auger in the hole. This is less timing consuming and less complicated than the procedure needed heretofore.

Preferred andlor optional features of the invention aresetforth in claims 2-13.

The invention will now be more particularly described with reference to the accompanying drawings, in which: Figure 1 is a side view of one embodiment of a drilling rig according to the invention,with the mast shown in a lowered transportable position; Figure 2 is a side view of the rear part of the drilling rig of Figure 1,withthe mastshown in a raised rig operation position, and Figure3 is a plan view of the drilling rig of Figures 1 and 2, with the mast shown in a lowered position and the elongate drive member omitted, but with the rotary drive member in an operating position as if the mast was in a raised position.

Referring nowto the drawings, the drilling rig shown therein comprises a support structure in the form of a trailer chassis 10 having a single axle 11 mounting wheels 12. Three screw operated jacks 13 are mounted on the chassis for levelling the chassis and stabilizing the rig during a drilling operation.

A single pole telescopically extendible mast 14 is pivoted at 15to the upper end of a post 16fixed tothe chasses 10 at the rear end thereof. A manually operable ratchet winch 17 is mounted atthefootofthe post 16 and is connected bya wire 18to a lug 19 atthe base ofthe mast, for raising the mast from a lowered generally horizontal transportable position (Figure 1 ) in which the upper end ofthe mast is supported in a bifurcated carrier 20 at the upper end of a post 21 fixed tothefront end ofthetrailer, and a raised substantially vertical position (Figure 2).The mast can be locked in one oftwo positions when raised depending on whetherthe mast is extended or not by inserting a pin 22athrough aperture 22 in a flange 24 ofthe post 16 and through an aperture 23 or 23a in the lug 19. Wire stays 25 connectthe upper end of the mastto upstanding lugs 26 on the chassis and when the mast is in a raised position these stays are held taut to stabilisethe mast.

An elongate drive member or Kelly, as it is known in the art, 27 is connected to a winch 28, mounted on the chassis, byaflexible elongate membersuch as awire 29 which passes over a sheave 30 freely rotatable at the upper end of the mast. A hood 31 fixed to the top of the mast extends over the sheave to keep the wire 29 in position on the sheave.

The Kelly 27 is rotatably driven by a rotary drive device 32. The latter comprises a housing 33 and a table 34 mounted for rotation in the housing 33. The table 34 has a through bore 35 receiving the Kelly27.

The Kelly 27 and bore 35 have corresponding noncircular, typically square, cross-sections. The Kelly 27 has a collar at the lower end so that to all intents and purposes the rotary drive device is permanently mounted on the Kelly.

Aworm 36 is supported by the housing 33 and engages a worm wheel (not shown) in the housing 33 and connectedtothetable 34. During a drilling operation the housing 33 is received between guides 38 fixed to the chassis and the housing 33 is fastened to the chassis by a releasable fastener or latch mechanism (not shown).

The powerdriveforthe winch 28 and forthe rotary drive device 32 may betaken, forexample, from an internal combustion engine 39 mounted on the chassis orfrom a powertake offshaft39' of a tractor vehicle. The power drive is connected to an input of a drive splitter box 40 having two output drives connected respectivelythrough clutches 40a and 40bto manual 5-speed (4 forward and 1 reverse) standard automotive gear boxes 41 and 42. The gear box 41 is connected to a drive shaft43, the rear end of which can be coupled to the worm 36 using a quick release fastener. The gear box 42 is connected to the winch 28 buy a drive shaft 44 and worm and wheel reduction box 37.

The winch 28 is fitted with a brake 50 and a clutch 51.

Acontrol panel 44is mounted atthe rear of the trailer and has three layers, namely a first lever to operate the winch brake 50, a second lever to operate the winch clutch 51 and a third leverto operate a clutch 40a of the rotary drive device. Gear selection is made by a manual selector lever on each respective gear box 41, 42. It is therefore possible to select an appropriate line speedforthewinch and an appropriate speed and hence torque for the rotary drive device.

The mast 14 is provided with a slot 45 to receive a lug 46 (Figure 1) fixed to the housing of the rotary drive device in order to locate the latter when the mast is in its lowered position.

The mast 14comprises inner and outer box-section parts 47 and 48 respectively. The part 47 istelescopi callyslidable inthe part48 and can be manually extended relativetothe part48. The parts 47 and 48 can be locked in anyone of a number of preselected positions bypassing a peg (not shown) through aligned apertures in the two parts.

The Kelly 27 may be telescopically extendible. Such a Kelly is particularly useful when drilling with an auger. However, due to the difficulty of providing adequate sealing it is unlikelythatsuch a Kelly would be fitted with a system for circulating mud or air through the hole being drilled to remove spoil.

Therefor, a non-extendible Kelly provided with a circulating swivel 27a (Fig. 2) for circulating mud and air could be provided for drilling the drill rods and rotor bits.

The drilling rig can be transported to a drilling location inthecondition shown in Figure 1.The mast 14 is then raised and locked in position. An auger or drill bit and swivel is coupled tothe Kelly. The rotary drive device 32 is located between the guides 38 and fastened to the chassis by the releasable fastener or latch mechanism. The worm 36 is connected to the drive shaft43 bythequickreleasefastener. Drilling can then commence. When drilling with an auger, spoil can be removed fromthe auger by simply removing the quick release fastener connecting the worm to its drive shaft and releasing the fastener or latch which fastens the rotary drive device to the chassis, raising the Kelly and auger and swinging them awayfrom the centre line of the hole,whereupon the spoil is removed by banging or shaking.

The arrangement of the rotary drive device on the Kelly also facilitates movement ofthe Kelly from the centre line of the hole in orderthata casing can be lowered into the hole and it also facilitates the insertion and removal of drill rods.

Instead oftheworm 36 and worm wheel, bevel gearing could be provided between the drive shaft43 and the table 34 ofthe rotary drive device, butthe advantage of the worm and worm wheel arrangement isthat itgives greaterflexibilityof use of prime mover in terms of speed andtorques to the rotary drive device because ofthe large choice of gear ratios availablefortheworm and worm wheel.

Although the support structure is shown in the form of a trailer chassis, the support structure could be mounted, forexample, on a truck, crawler, tractor, barge, platform or skid.

The drilling rig as described above is ideally suited for use in developing countries. It is easilytransportable; indeed it can be transported byhelicopterto inaccessible locations. With no hydraulic parts, it is easily maintained and it uses parts which are readily available even in developing countries. Moreover, it could be supplied in kit form for local assembly.

Claims (14)

1. A mobile drilling rig comprising a support structure, a mast pivotably mounted on the support structure for movement between a raised rig operating position and a lowered transportable position, a winch mounted on the support structure, a rotatable elongate drive memberfor supporting a drilling device and being suspended from the mast by a flexible elongate element connected to the winch, a rotary drive device for rotating the elongate drive memberaboutthelongitudinal axis ofthe elongate drive member, meansfordriving the winch, means for driving the rotary drive device, and means for releasablycoupling the rotary drive device to its drive means, the rotary drive device being mounted about the elongate drive member so that when a drilling operation isto be performed and the rotary drive device is coupled to its drive means the elongate drive means is rotated by the rotary drive device whilst being able to move vertically or substantially vertically therethrough and the rotary drive device being carried bythe elongate drive memberso that it can be uncoupled from its drive means and swung as one unitwith the elongate drive memberawayfrom the centre line of a hole being drilled.

2. The drilling rig of claim 1,wherein the rotary drive device comprises a housing and a table which is mounted for rotation in the housing and which has a bore therethrough receiving the elongate drive mem ber,the bore and elongate drive member being of corresponding non-circular cross-section.

3. The drilling rig of claim 2, wherein the table is connected to a worm wheel drivable by a worm.

4. The drilling rig of claim 3, wherein the worm is part ofthe rotary drive device and can be coupled to an uncoupledfrom the drive meansforthe rotary drive device.

5. The drilling rig of any one of the preceding claims, further comprising means for releasably fastening the rotary drive device to the support structure.

6. The drilling rig of any one of the preceding claims, wherein the mast is a single pole mast.

7. The drilling rig of claim 6, wherein the single pole mast is telescopically extendible.

8. The drilling rig of anyone ofthe preceding claims,furthercomprising a manually operable winch for raising the mast.

9. The drilling rig ofanyoneofthe preceding claims, wherein flexible elongate stays are connected between the support structure and the upper end of the mastto stabilisethe mast in a raised position.

10. The drilling rig of any one ofthe preceding claims, wherein the elongate drive member is telescopically extendible.

11. The drilling rig of any one of the preceding claims, wherein the drive means forthe winch and the rotary drive device comprise a drive splitter having a single input for connection to a prime mover and two outputs respectively connected to two gear boxes and clutches.

12. The drilling rig of any one ofthe preceding claims, wherein the support structure is in the form of a chassis having at least one axle supporting ground engageable wheels.

13. The drilling rig of any one of the preceding claims, wherein the supportstructure is provided with a plurality of jackeing devicesforstabilising the support structure during a drilling operation.

14. Amobiledrilling rig substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.