HYDRAULIC DOWN-THE-HOLE ROCK DRILL

Abstract: Method and apparatus for drilling deep holes in the rock or the like. The apparatus is adapted to be attached to the end of a drill string (1) and be sunk to the bottom of the bore hole (27). The apparatus comprises a pilot control unit (B), a hydraulic engine (12), a hydraulic pump (16), and impact apparatus (21) and a drill bit (23). Drilling mud which is fed down through the drill string to flash up the cuttings drives the hydraulic engine which is of a robust construction and will withstand the abrasive drilling mud. The output shaft (15) of the engine drives the hydraulic pump which pumps high grade hydraulic fluid to the impact apparatus which is a hydraulically driven hammer rock drill of known construction. The impact piston strikes against the drill bit. The whole apparatus is rotated by means of a rotary machine placed on the ground level. Due to the pilot control unit (B) the apparatus only has to carry its own dead weight and openings and valves provide a bypass and stopping, respectively, of the drilling mud.

Description: HYDRAULIC DO N-THE-HOLE ROCK DRILL * Technical Field The present invention refers to a hydraulically operated down-the-hole rock drill adapted for drilling deep, thick and rough holes in the rock and in firm ground. Background Art Today so-called rotary drilling is mainly tsed when drilling holes of the type mentioned above, which means that a specially shaped drill bit is pressed down and simultaneously rotated into the ground. Due to the fact tha the drill bit is provided with inserts of different shapes, the rock or eart material is crushed or ground. Usually the drill bit is mounted on a tubular drill string, the .diameter of which is smaller than the diameter of the dril bit: The drill string is imparted a rotational movement by means of a machin assembly placed above ground. This machine assembly also comprises means for supporting the drill string. The rock and earth material (called the cutting ground by the drill bit is transported to the ground level by flushing with water or any specially composed washing or flushing fluid, so called drillin mud. The flushing is performed by pressing the drilling mud by means of a pu through a centre hole in the drill string and through flush openings in the drill bit at the bottom of the bore hole, whereupon the drilling mud flows to the ground level on the outside of the drill string and thus carries away the cuttings. At the ground level the main parts of the cuttings are separa¬ ted from the drilling mud, e.g. by settling the mud in basins, whereupon it is again pumped down through the drill string. It is also knov/n to perform rotary drilling by using an engine which is sunk down into the bore hole and is attached to the lower end of the drill string, which is non-rotating. The engine is directly driven by the drilling mud. O PI Rotary drilling of the above type is mainly used for soft sedimentary rock types. When drill ng in harder crystalline rock, the method is expen¬ sive since the drilling rate will be very low and the wear of the drill bit severe. To this type of rock a completely different drill ng method is used called hammer drilling, which means that an impact piston is brought to str ke against the drill string and/or the drill bit at a high frequency and th drill string is simultaneously slowly rotated. The machines used for this application are usually driven by compresse air, i.e. the impact piston is driven by compressed air. The compressed air is normally also taking care of the flushing up of the cuttings. When drill ing deeper and thicker holes (up to about 200 ) this method uses a so-call sinker hammer, which means that the bore hammer with its impact piston is mounted on a tubular drill string and is sunk down into the bore hole by me of a rotary machine with essentially the same construction as the one descri above for rotary drilling. At hammer drill ng the compressed air is taken from an air compressor on the ground level and is blown through the drill string and driving the i pact piston, which directly strikes against the drill bit, whereupon the c pressed air flushes the cuttings up to the ground level outside the drill string. One drawback of this method is that its capacity of deep drilling i limited. However, the method is substantially faster than rotary drilling, especially in hard rock. In later years hydraulically driven hammer rock drills have been de¬ veloped, which in principle differ from the compressed-air driven hammer drilling machines by the fact that the impact piston is operated by hydrau lic oil under high pressure. The flushing of the cuttings is taken care of separately by compressed air or a drilling mud. Such hydraulically driven hammer rock drills have so far only existed in the form of so-called "abov ground machines", i.e. with the bore hammer machine working in a machine u placed on the ground level. Thus, these machines have a limited capacity i drilling deep and thick holes. However, theirdrill ng capacity is substant ly higher than the capacity of the compressed-air driven at the same energ consumption. It is desirable to use a sinkable hydraulically driven hammer rock dr to drill deep and rough holes at high speed. Hov/ever, this has so far not possible as the long hydraulic cables to the hammer rock drill at deep hol imply too great losses. As mentioned above the cuttings must be removed from the hole, which with regard to deep holes always is performed by means of a drilling mud since the hydrostatic pressure in the hole is too great to use compressed It might be possible to use the drilling mud in order to drive a hydraulic hammer rock drill but this would be out of the question to a skilled perso No matter how careful the drilling mud is ' settled before it is recirculate the drilling mud always contains great amounts of sand and abrasive partic les which would rapidly abrade and destroy the valve mechanism of the hamm rock drill. Such a hammer rock drill must be driven with clean hydraulic oi and especially when one wishes to drive the hammer rock drill at high pres sures, in the order of 150 bar, the hydraulic oil must be of a very high grade. Disclosure of invention In accordance with the present invention the drilling mud drives a ro bust hydraulic engine placed immediately in connection with the drill bit in the bore hole. The output shaft of the engine is used to drive an impac apparatus which strikes against the drill bit, i.e. so.called hammer dril¬ ling. If the impact apparatus is hydraulically driven the output shaft of the engine is adapted to drive a hydraulic pump to provide high pressure hydraulic fluid to the impact apparatus. The hydraulic fluid is thus enclo¬ sed in a closed circuit and a very clean hydraulic oil of high grade may be used in order to guarantee a safe operation. The hammer rock drill in accordance with the invention which has been sunk down, may be brought to rotate by means of a machine unit placed at • the ground level or alternatively, the output shaft of the hydraulic en¬ gine may also provide rotation of the drill bit. It is an advantage that the drill bit only carries the load of the hydraulic engine and the impact apparatus and is independent of the length of the drill string supplied in the hole, which easily can be provided by means of a pilot control. The present invention also relates to an apparatus for carrying out the above mentioned hammer drilling. Brief description of drawings The invention is described in detail below with reference to the ac¬ companying drawings, in which Fig. 1 is a longitudinal view in section of one embodiment of the invention and Figs. 2 to 7 are cross-sectional views of the embodiment of Fig. 1 taken along the lines II-II, III-III, IV-IV, V- VI-VI and VII-VII. Best mode of carrying out the invention and industrial applicability The apparatus mainly consists of seven interconnected or integral units, which in Fig. 1 are denoted A - G. Unit A consists of a tubular drill string of known construction, which is composed of separate pieces interconnected by means of tapered thread joints and extends to the ground level. The drill string is brought ro rotate by means of a machine unit on the ground level, which also com¬ prises devices of known contruction for inserting and taking up the drill string of the bore hole. The drill string is dimensioned to withstand not only any appearing torque or axial forces but even a comparatively high in¬ side hydraulic pressure from the drilling mud. Unit B consists of a feeding or pilot control unit by means of which it is assured that the drill bit is pressed against the bottom of the bore hole with an adequat force. Unit C consists of a hydraulic engine of known construction, which during an acceptable time of life may be driven by means of the hydraulic energy of the drilling mud. This drilling mud may be water or any other drilling mud or liquid and 1s mixed with soil particles. The length of the hydraulic engine is great compared to its diameter. Unit D consists of a hydra!ic pump of known construction, but with a special construction. The hydraulic pump emits clean high pressure hydrau¬ lic, oil. Unit E consists of an oil tank with an oil filter. The length of the oil tank is great compared to its diameter and it is provided with passa- ges in the wall of the tank for the drilling mud and the hydraulic oil. Unit F consists of a hydraulically driven hammer rock drill, whose fundamental mode of action with regard to the impact mechanism does not differ from known constructions. In this case the hammer rock drill is adapted to be able to work as a sinkhammer downwards in the bore hole, and so it is i.a. provided with flushing passages for the drilling mud and an adapter for transferring of torque, axial forces and strokes directly to the drill bit. Unit G consists of a drill bit of known construction including inserts or pins made of hard carbide steel as well as flushing passages for the drilling mud. The apparatus of the invention comprises a drill string 1, which con¬ sists of a number of interconnected drill strinc sections. The drill string 1 is the connecting link to the ground level. The pilot unit (B) is connec- O P ted to the drill string. This consists of a top unit 2, a cylinder tube 3 and a base unit 4, all units being interconnected by means of thread joints. The lower portion of the cylinder tube 3 is provided with four circumferentially spaced openings 5. The base unit 4 is provided with a square passage 6. A piston 7 is movably arranged inside the cylinder tube 3 and sealed thereagainst. The piston is fixedly attached to a piston rod 8, which is tubular with a square outer shape. The piston rod 8 runs with a small or loose fit in the square passage 6 of the base unit 4. The upper portion of the piston rod is provided with a valve mechanism 9, consisting of a cylindrical tube with a valve opening 10. This cylindrical tube is closed at the top end and fits closely in a cylindrical hole 11 in the top unit 2. Drilling mud is pressed through the boring tube 1, and the direction of the drilling mud appears from the solid line arrows in Fig. 1. Usually the drilling mud flows through the valve openings 10, through the piston rod 8, which is hollow and through a hydraulic engine 12. Simultaneously the drilling mud presses the piston 7 downwards as the fluid pressure is lower in the cylinder tube 3 under the piston 7, which space communicates with the bore hole outside the cylinder tube. The hydraulic engine 12 is provided with an inlet opening 13 and an outlet opening 14 for the drilling mud and is also provided with an outlet shaft 15 which is brought to rotate when the drilling mud flows through the engine. The engine is of a well-known construction and will not be de¬ scribed more closely herein. Any engine may be used that can be driven by the drilling mud without being destroyed in a short period of time. The outlet shaft 15 of the hydraulic engine is connected to the inlet shaft 17 of a hydraulic pump 16. When the drilling mud reaches the hydrau¬ lic engine, the engine is rotated and so is the hydraulic pump. This means that the hydraulic pump emits high pressure hydraulic oil (15-20 Pa) to a damping accumulator 19, which is comprised in the hammer rock drill 18. The hydraulic oil is transferred to a slide mechanism 20 of the hammer rock drill, the construction of which implies that an impact piston 21 is given a rapid reciprocating impact movement. The impact piston 21 strikes with its lower portion against an adapter 22, at which the drill bit 23 is firmly threaded. The impact from the impact piston is thus transferred to the drill bit, which crushes soil or rock material in the bottom of the bore hole. The hydraulic oil is returned from the slide mechanism 20 to an oil tank 24 and thence back to the hydraulic pump 16. The path of the hydrau - ζjRlX O PI lie oil appears from the dotted arrows in Fig. 1. When the drilling mud has left the hydraulic engine 16 it is transpor¬ ted through passages 26 past the oil tank 24 and the hammer rock drill 18 to the adapter 22 and out through a flushing hole 25 in the drill bit 23. The bottom of the bore hole is flushed from crushed material (cuttings), which is carried by the drilling mud upwards along the outside of the ap¬ paratus between the apparatus and the wall 27 of the bore hole up to the ground level, where the drilling mud is collected in separate basins in which the main part of the cuttings is separated from the drilling mud whereupon it is pumped down once again through the drill string. The torque from a rotary machine (not shown) placed at the ground level is transferred through the drill string 1 and the pilot unit(B)throug the square passage 6 and the square piston rod 8 to the other integral unit C-F. From the hammer rock drill (F) the torque is transferred to the adapte and the drill bit 26 since the adapter is provided with splines 28. The operation of the apparatus according to the invention is as follow When the drilling is to be started the apparatus is connected by means of thread jounts to a rotary machine placed on the ground level, whereupon the apparatus is sunk down into the bore hole until the drill bit reaches the ground level or the bottom of the bore hole. At continued sinking of the drill string 1, the top unit 2 moves towards the valve mechanism 9, of which the outside cylindrical part is inserted into and cooperates with the upper cylindrical holes 11 of the top unit with a good fitting. In this way the inner channel, i.e. the cylindrical hole 11, of the drill string is sealed so that the drilling mud is prevented from passing further through the pis¬ ton rod 8. Thereafter the drill string 1 is lifted a small distance until the top edge of the valve mechanism 9 exposes the cylindrical hole 11 in the top unit and gives free passage for the drilling mud. Simultaneously, the rotary machine starts to rotate the drilling string and thus the appa¬ ratus as well as starts the pump placed at ground level for the drilling mud. Thereafter the hydraulic engine and the hydraulic pump set the impact piston into operation and the hammer rock drill is moved downwards as the drill bit crushes soil or rock material. The drill string 1, the top unit 2 and the cylinder tube 3 rotate without moving vertically. The feed pressure on the drill bit 26 only consists of the dead weight of the units C-G, the piston 7 and the piston rod 8, and the hydraulic differential pressure on the top of the piston 7. When the drill bit and thus the piston 7 has sunk so deep inthe bore hole that the piston has passed underneath the openings 5 in the side of the cylinder tube 3, the drilling mud flows out through these openings and further up to the ground level on the outside of the apparatus. This en- 5 tails that the hydraulic engine 12 and thus the impact piston 21 stop, whic means that the back pressure of the drilling mud decreases due to the lower flow resistance, as it does not have to pass through the hydraulic engine 12. This may be monitored by means of for example a manometer at the pump on the ground level. When this has been taken care of the drill string 1 is 10 again lowered downwards into the bore hole by means of the rotary machine. As the drill bit rests on the bottom of the bore hole the piston 7 will once again cover the openings 5 in the side of the cylinder tube 3 making the drilling mud to pass through the piston rod 8 to the hydraulic engine 12, and the impact piston starting to strike against the adapter and the 15 drill bitI When the drill string has been sunk so far that the valve me¬ chanism 9 seals the cylindrical hole 1.1 in the top unit 2 the hydraulic pressure of the drilling mud is instantaneously raised. At this moment the drill string 1 is lifted a small distance until the passage for the drilling mud is free, whereafter the drill string is vertically kept un- -20 movable and is only rotated until the drill bit and thus the piston 7 once again reaches below the openings 5 and the cycle is repeated. The step-by-step sinking of the drill string 1 into the bore hole a distance corresponding to the piston stroke may be done automatically for example by means of the mechanism of the rotary machine which performs the 25 vertical movements of the drill string (feed unit). This mechanism may be adapted to sink the drill string when the hydraulic pressure instantaneously decreases in the drilling mud and to stop when the pressure instantaneously increases in relation to preset values. The drill string may also be fed with a constant preset feeding rate, the feeding rate being modified by the 30 sensor signals disclosed above. Thus, the apparatus provides a comparatively constant and limited pres¬ sure on the drill bit during drilling, which is desired for example in or¬ der to decrease the wear of the drill bit and the torque required. Moreover, it is prevented that the inpact piston strikes against the drill bit when- 35 it is not resting on the bottom of the bore hole, which is essential in or¬ der not to damage the drill bit. Furthermore, the pilot control makes it possible for the drill string to move vertically a limited distance during drilling if the pump for the OMPI drilling mud is provided with an overflow valve, so that the drilling mud overflows at the pump on the ground level, if the pressure in the drilling mud exceeds a preset value. This makes it possible for example to perform drilling with a drilling machine mounted on a raft which is moving verti- cally during high sea. One preferred embodiment has been described above. Apparently differen modifications and alterations may be made of the described apparatus within the scope of the invention. For example the hydraulic pump may be any known type of pump, e.g. a diagragm pump. Alternatively the hydraulic engine and the hydraulic pump may be replaced by two mechanically interconnected hy¬ draulic cylinders, one of which works as an engine and is driven by the drilling mud and the other works as a pump for the hydraulic oil. By choos¬ ing a suitable ratio for the cross-sectional areas of the two hydraulic cy¬ linders of e.g. 3:1 the desired pressure for the hydraulic oil may be ob- tained.The slide and valve mechanism of the hydraulic pistons may be in¬ terconnected for mutual movement. The apparatus in accordance with the invention is intended for drill¬ ing very deep holes, e.g. drilling for oil. Especially at drilling for oil at sea, the costs of operation per day are very high. For this reason the apparatus in accordance with the invention only has to be constructed in such a way to safely manage to drill one complete bore hole, after which operation the apparatus may ge discarded. However, if the apparatus stops working or gets stuck when the drilling of the hole has come half way, the costs for taking up the apparatus or possibly drill a new sloping hole ad- jacent the apparatus that has got stuck may be very high. Due to the fact that the apparatus in accordance with the invention manages a bore rate which is approximately twice the bore rate of known drills for drilling oil, a substantial saving may be obtained when drilling such deep holes, especially when drilling forOil at sea. Thus, the invention described above refers to a method and an appara¬ tus for making bore holes in the ground or rock where the drilling mud has the double function of driving a hydraulic hammer rock drill at the bottom of the bore hole on the one hand, and on the other hand to flush out crush¬ ed soil or rock material from the bore hole. Due to the invention it will now be technically possible to make bore holes of up to several thousand meters depth with a hammer rock drill where an impact piston strikes the drill bit which is simultaneously rotated. This means that the drilling capacity (drilling rate) with regard to known methods may be doubled and in some cases even tenfolded, i.a. depending on the hardness of the rock. O Π

Claims: C L A I M S 1. Method for drilling deep holes in the rock or the like, where the hole is drilled by means of a drill bit attached to one end af a drill string and the cuttings obtained during drilling are removed from the hole by means of a drilling mud, which is forced down through the drill string and flushed through the drill bit and is pressed out of the hole, c h a¬ r a c t e r i z e d in that the energy of the drilling mud is partly used to drive a hydraulic engine (12) placed immediately in connection with the drill bit (23) in the hole and that the output shaft (15) of the engine is used to drive a hydraulic impact device which delivers a plurality of strokes to the drill bit, so-called hammer drilling. 2. Method in accordance with claim 1, c h a r a c t e r i z e d in ! that the output shaft (15) of the hydraulic engine drives a hydraulic pump (16) which pumps hydraulic fluid to a hydraulically driven impact piston (21) in the impact device. 3. Method in accordance with claim 2, c h a r a c t e r i z e d in that the hydraulic pump (16) pumps high pressure hydraulic oil to a pressure accumulator (19) for equalization of the pressure; and that the drill bit is brought to rotate by means of an engine placed on the ground level, the rotation of which is transfrerred to the drill bit by the drill string or alternatively that a part of the energy of the hydraulic engine is used to rotate the drill bit in the hole with regard to the drill string, which in this place is not rotated. 4. Method in accordance with any of the precious claims, c h a r a c¬ t e r i z e d in that the feeding rate of the drill string down into the hole is controlled in dependence of the boring rate of the drill bit, the drill bit substantially only carrying the dead weight of the hydraulic en¬ gine (12) and the impact apparatus and possibly the hydraulic pump with the accumulator, and that the impact apparatus is prevented from striking against the drill bit while not resting against the bottom of the bore hole 5. Apparatus for drilling deep holes in the rock and the like, com¬ prising a drill bit (23) attached to the end of a drill string (1) through which a drilling mud is flowing to transport the cuttings obtained at the drilling out of the hole, c h a r a c t e r i z e d by a hydraulic engine (12) which is adapted to be driven by a part of the energy of the drilling mud and is placed immediately in connection with the drill bit (23) and an impact apparatus (21) which is driven by the hydraulic engine (12) and strikes against the drill bit (21). 6. Apparatus in accordance with claim 5, c h a r a c t e r i z e d in that the hydraulic engine (12) is adapted to drive a hydraulic pump (16) which pumps high pressure hydraulic fluid to the impact apparatus (21) which is a hydraulically driven hammer rock drill. 7. Apparatus in accordance with claim 6, c h a r a c t e r i z e d in that a pressure accumulator (19) is connected to the output shaft (14) of the hydraulic pump (14) for equalizing the pressure of the hydraulic oil; and a device placed on the ground level to rotate the drill string and thus the drill bit, or alternatively that the outlet of the hydraulic engine is arranged to drive a rotary device in the apparatus to rotate the drtTT bit in relation to the drill string which is not rotated. 8. Apparatus in accordance with anyone of claims 5, 6 or 7, c h a¬ r a c t e r i z e d by a pilot control unit (B) which is arranged to load the drill bit at drilling substantially only with the dead weight of the hydraulic engine (12) and the impact apparatus and possibly the hydraulic pump with the pressure accumulator, and to prevent the impact apparatus to strike against the drill bit while not resting on the bottom of the bore hole. 9. Apparatus according to claim 3, c h a r a c t e r i z e d in that the pilot control unit (B) makes it possible for the drill string to move vertically during drilling without appreciably effecting the load on the- drill bit. 10. Apparatus in accordance with claim 8 or 9, c h a r a c t e r i¬ z e d in that the pilot control unit (B) is arranged to feed the drill string (1) with a speed depending on the speed with which the drill bit works its way down, the feeding being performed intermittently and/or continuously.

Inventors: NYMAN KARL-ERIK, NYMAN, KARL-ERIK
Applicants: NYMAN KARL ERIK, NYMAN, KARL-ERIK
Application year: 1982
Main classification: E21B4
IPC codes: E21B4