"DRILLING APPARATUS" FIELD OF THE INVENTION THIS INVENTION relates to drilling apparatus. BACKGROUND OF THE INVENTION

A constant problem in relation to conventional drilling apparatus is to provide an efficient means of dewatering bore holes. One means of achieving this in relation to well established bore holes is to lower down the bore hole a pneumatically operated turbine pump having an air line as well as a water delivery conduit. This method, however, needed to be constantly maintained and was not suitable for bore holes which were relatively small or were of insufficient diameter to allow the drilling apparatus to be lowered down the bore hole. In this latter context, use of a pneumatically operated turbine pump could not be appropriate because the pump could not get access to the excess water in the bore hole.

Conventional reverse circulation drilling apparatus which includes passing pressurized fluid down an annular space surrounding a central drill tube and passing the pressurized fluid up the central drill tube entrained with mined material is well known. Such drilling apparatus also usually includes drilling jets utilizing the pressurized fluid which is usually water. Examples of such drilling apparatus are described in Australian Specifications 26491/77, 523505, 77965/91 and 59596/80 as well as U.S. Specifications 4915452 and 5125464. However, to date, such reverse circulation drilling apparatus has not been effective in removal of waste water from bore holes of relatively small diameter.

SUMMARY OF THE INVENTION It therefore is an object of the invention to provide drilling apparatus which may alleviate this problem.

Drilling apparatus of the invention includes:

(i) a drill string including a central tube surrounded by at

least one outer tube; (ii) a drill head including a centrally located lift jet; (iii) a plurality of access passages located in the drill head above the lift jet for passage of mined material above the central tube;

(iv) one or more cutting jets associated with a high pressure fluid; and (v) valve means for closing flow of high pressure fluid to said one or more cutting jets. Preferably, there is provided a venturi in the drill string above the drill head which may function in combination with the lift jet to transfer mined material to the top of the bore hole.

In one embodiment, the drill string includes a central tube surrounded by an outer tube to define an annular space. The annular space is preferably connected to a high pressure fluid source whereby high pressure fluid and more preferably high pressure water is passed down the annular space.

In a second embodiment, the drill string includes a central tube surrounded by an intermediate tube and an outer tube to provide an outer annular space and an inner annular space. The outer annular space may be connected to a source of high pressure fluid such as pressurized air and the inner annular space may be connected to a source of high pressure fluid such as water.

In the first embodiment, the high pressure water may provide one or more suitably a plurality of cutting jets which may be located in the drill head above the lift jet. The valve means is effective in closing the flow of high pressure water to the cutting jets when required which enables the lift jet to be used for dewatering the bore hole in association with the venturi. In the second embodiment, air jets may be associated with the pressurized air in the inner annular space and water jets or cutting jets associated with the pressurized water in the outer annular space.

Primary valve means may be associated with the air jets to close flow of high pressure air to the air jets when required and secondary valve means may be associated with the water jets to close the flow of high pressure water to the cutting jets. However, in another embodiment, a common valve means may be associated with both the air jets and the water jets to close one or the other when required.

In this arrangement, the water jets may be turned off and the air jets turned on to facilitate dewatering of a bore hole. High pressure air may also be passed outside the drill string for dewatering purposes.

The valve means as described above may be of any suitable type such as a ball valve but for the sake of convenience, it is preferred to use a slide valve whereby a valve member may shut off fluid passageways to the pressurized jets, which valve member may be operated hydraulically, pneumatically or by pressurized water.

BRIEF DESCRIPTION OF THE DRAWINGS Reference may be made to a preferred embodiment of the invention as shown in the attached drawings wherein:

FIG. 1 is a view of one form of drilling apparatus constructed in accordance with the invention showing the full length of the drill string and high pressure pump and mineral separator communicating with the drill string by associated manifold and conduits;

FIG. 2 is a cross section through the drilling apparatus of FIG. 1 along the line A-A; FIG. 3 is a detailed view or longitudinal section through the drill head and adjacent drill string of the drilling apparatus of FIG. 1;

FIG. 4 is a half section through the drill head of FIG. 3 along the line B-B;

FIG. 5 is a sectional view through the drilling apparatus of FIG. 1 along the line C-C;

FIG. 6 is a view of another form of drilling apparatus constructed in accordance with the invention utilized for underwater

drilling;

FIG. 7 is a detailed view or longitudinal section of the drill head and adjacent drill string of the drilling apparatus of FIG. 6; and FIG. 8 is a section through the line D-D of FIG. 6. DETAILED DESCRIPTION

In the drilling apparatus 10 shown in FIG. 1 , there is shown drill string 11 comprising drill string sections 12 and 13 and releasable coupling 14. There is also shown drill head 15, water jets 16, access apertures 17 for mined material, vibrator 18 which is pneumatically operated to transmit vibrations to drill head 15 to assist withdrawal of drill head from an area 19 being mined and associated air line 18A, high pressure pump 20 and associated conduit 21 which transfer water under high pressure to manifold 23 wherein high pressure water is transferred to annular space 25 surrounding inner drill tube 24, primary mineral separator 22 and associated conduit 26 for transfer of mixed material from inner drill tube 24 to primary mineral separator 22, tailings conduit 27 for transfer of tailings from primary mineral separator 22 which may be used for filling up a previously drilled hole (not shown) and outer drill tube 28. Valve assemblies 29 are also shown for controlling water flow through water jets 16. There is also shown curved transfer tube 30 interconnecting conduit 26 and inner drill tube 24.

FIG. 2 shows the orientation of water jets or cutting jets 16 in relation to outer drill tube 28 and inner drill tube 24. There is also shown venturi 30A and central jet 31 hereinafter described. FIG. 3 shows the operation of drill head 15 in greater detail and valve assemblies 29 include control lines 32 and 33, cylinder 34, piston 35, piston rod 36, opposed valve housings 37 and 38, valve member 39 attached to piston rod 36, passageways 39A for transfer of high pressure water from annular space 25 to jets 16, seals 40 and high pressure water tubes 42 interconnecting high pressure water chamber 42A to lower drill member 43 which has a frusto-conical section 44 and conical drill tip 45.

There is also shown central jet 31 located in lower drill member 43, replaceable wear plate 47 which is attached to lower drill member 43, access passages 17 for entry of mined material which are located at 120° intervals around the periphery of drill member 43 and venturi 30A. There is also provided adjustable pin 47A for preventing entry into venturi passage 30B of boulders or rocks which are larger than passage 30B.

There is also provided flange 49 for interconnecting outer drill tube 28 to housing 50 by bolts (not shown). Housing 50 encloses high pressure water chamber 42A and flange 51 interconnects housing 50 and lower drill member 43 by bolts (not shown). Lower drill member 43 has flange 52 which mates with flange 51 as shown.

In FIG. 4 the orientation of venturi tube 30A in relation to access passages 17, inner tube 24 and outer tube 28 is indicated. In FIG. 5 there is shown a detailed view of releasable coupling 14 wherein high pressure water is passed along annular space 25 in a plurality of elongate passages or narrow tubes 54. Releasable coupling 14 may include a pair of opposed flanges 55 interconnected by bolts 56. In FIG. 6 there is shown another form of drilling apparatus

60 constructed in accordance with the invention primarily used for seabed mining or mining underwater. The drill string 61 has releasable coupling 62 and is associated with a drill vessel 63 having tower 64 for processing mined material obtained from the seabed. The enriched wash may be treated on vessel 63 or may be off-loaded to barges. The vessel 63 has control tower 65.

The drilling apparatus 60 is characterized in having a drill head 66 having a plurality of high pressure air jets 67 and a plurality of high pressure water jets 68. A more detailed view of drilling apparatus 60 is shown in

FIG. 7 and it will be noted that drill string 61 includes an outer drill tube 69, intermediate drill tube 70 and inner drill tube 71. High pressure air

travels down outer annular space 72 and high pressure water travels down inner annular space 73.

High pressure water from annular space 73 may exit through water jets 68 while high pressure air from annular space 72 may exit through air jets 67. There is also provided valve assemblies 74 which function in the same manner as valve assemblies 29 previously described for controlling flow of water through water jets 68. Thus a valve member (not shown) from each valve assembly 74 may cut off air flow by reciprocal movement along passages 75. Control of air flow through air jets 67 may be effected by use of a flow control valve (not shown) which controls flow of air through outer annular space 72.

There is also provided an air piston vibrator 77 having opposes anvil 78 and a piston 80 which may undergo reciprocable movement in piston housing 81 to vibrate drill head 66 which has the desirable effect of preventing particles such as stones or gravel in mined material from staying dormant around gravel accessways 83. This enables the drill string 61 and associated drill head 66 to be rotated easily in any direction. The piston vibrator 77 also has an exhaust hose 84 and a feed hose 85 communicating with exhaust aperture 86 and feed aperture 87.

There is also provided a support structure 88 for vibrator 77 which is bolted by bolts 89 to flange 90 which interconnects drill string 61 to drill head 66 which also includes jet housing 92 and lower conical member 93. Jet housing 92 includes a chamber 94 for pressurized air and a chamber 95 for pressurized water. There is also shown venturi 96, flange 97 and central lift jet 98. There is also shown adjustable pin 83A having the same function as adjustable pin 47A described previously. There is also provided wear plate 100. There is also shown water jets 101 , 102 and a third jet (not shown) wherein water jet 101 is inclined vertically, water jet 102 is inclined at 5° to the vertical and the third water jet (not shown) inclined at 2V_° to the vertical. The purpose of these jets is for sinking the drill string 61 whereby the drill head 91 cuts its own hole

in the seabed. Each of these jets may have slide valves similar to slide valve assembly 29 previously described for opening and closing of high pressure water or air or a mixture of pressurized air and water to the water jets 101, 102 and the third jet (not shown). Therefore, these jets may be connected to a source of high pressure water, high pressure air or a mixture of high pressure air and water. There is also shown arrows 103 showing the escape or release of high pressure water to the surface of the water.

In FIG. 8 there is shown details of releasable coupling 62 including opposed flanges 104 interconnected by bolts 105 together with air pipes or air hoses 106 in annular space 72 and water pipes or water hoses 107 in annular space 73. Air pipes 106 may have a round or substantially rectangular shape as shown and the same applies to water pipes 107. In operation of the drilling apparatus 10 shown in FIGS. 1-5, it will be appreciated that such apparatus may also be fitted with a high frequency vibrator adjacent drill head 15 in a similar manner as shown in FIG. 6 in regard to vibrator 77 being attached to drill string 61. Thus both drill strings 11 and 61 may be fitted with vibrators at top and bottom to facilitate rotation of drill heads 15 and 92 and also to ensure free movement of mixed material through access passages 17 and 83 respectively.

The drilling apparatus 10 is useful for mining of deep leads to obtain metal ore or minerals. The outer drill tube 28 may be formed from metal such as aluminium, stainless steel, or an alloy steel. The inner tube 24 may be formed from similar material or wear resistant composite material.

The drilling apparatus 60 may be utilized in an ocean seabed, river or estuary wherein it is usually impossible to dewater the area being mined by pumping.

In drilling apparatus 10 as described, high pressure water is passed in annular space 25 to drill head 15 wherein any number of jets

16 may direct the flow of water in a controllable angle from horizontal so that the jets of high pressure water are directed upwardly from horizontal. These jets cut and break up the enriched alluvial gravel as the drill head 15 is located in an appropriate position where it is known that an enriched wash is available at a particular depth.

The jets of water cut the alluvial wash and convert it to a slurry and the slurry flows towards inner tube 24 which is facilitated by the production of a vacuum or suction created by central water jet 31 whereby water is passed through venturi 30A. When the slurry contacts water from jet 31 from below, it is propelled at a fast rate up inner tube 24 for subsequent processing.

A pre-drilled bore hole is usually required in regard to drilling apparatus 10 from the surface wherein the pre-drilled bore hole passes vertically downwardly until it contacts bedrock and enters into the bedrock and locating an enriched wash which is usually located above the bedrock.

The operation of valve assemblies 29 is important which is usually controlled by an operator above the bore hole. If large quantities of ground water exist in the pre-drilled bore hole then such ground water may be removed by operation of central jet 31. When all the water is removed to the surface the operator then may operate valve assemblies 29 which are activated by water controlled pistons either internally or externally of the drill head 15. The jets 16 then may cut the enriched wash and the slurry wash may then be removed to the surface as described above.

In the operation of drilling apparatus 60, high pressure air is passed through annular space 72 to air jets 67 which are located above water jets 68. The air then expands and suitably has a higher pressure then the water pressure at the relevant depth. The air then displaces the water and this results in an air chamber being created surrounding water jets 68 whereby operation of water jets 68 may freely cut the alluvial wash. Valve assemblies 74 in this embodiment may function in a similar

manner to valve assemblies 29 previously described.

The three tube construction of drilling apparatus 60 makes it possible to mine metals, minerals and diamonds from deep ocean deposits. The drill strings 11 and 61 may be raised or lowered by any suitable means. Preferably if the cutting jets are used it is only necessary to rotate the drill strings 11 and 61 by 120° anti-clockwise and clockwise. In operation of drilling apparatus 60 part of the air escapes up the drill hole excavation and the passage of this air bails out surplus water as the drill hold excavation increases in size. The drilling apparatus 60 is useful for mining of diamonds in hard conglomerates whereby only the enriched wash is mined leaving the barren wash and overburden in situ.

In another aspect of the invention, there is provided a drilling apparatus with improved pressurized lifting capacity of mined material from a bore hole to the surface which includes the aforementioned central lift jet and preferably in combination with a venturi that may form part of the drill string or alternatively, be included in a drill head. The valve means for turning off the cutting jets is only a preferred option in this form of the invention.

A particular advantage of the drilling apparatus of the invention is that such drilling apparatus may cause very little, if any, damage to the environment. Thus vegetation is left substantially undisturbed and all ground apparatus such as pump 20 and primary mineral separator 25 are mounted on rubber tyres. Material discarded through tailings conduit 25 may be placed down a drill hole which was drilled previously to cause very little disturbance to existing vegetation.

In operation of the drilling apparatus of the invention, pre- drilling may be carried out by bucket drill or other appropriate drilling apparatus to determine the size of boulders or rocks so as to ensure that drilling apparatus 10 or 60 may operate at a particular mining location.