Method and equipment for drilling a cased borehole using a liquid-powered down-the-hole drilling apparatus
The drilling apparatus with a protruding welding shoe and enlarged wings, combined with viscosity enhancers, addresses deep drilling challenges by ensuring reliable debris removal and maintaining flushing rates, overcoming blockages and pipe sticking issues.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- TERRAMEK OÜ
- Filing Date
- 2025-12-12
- Publication Date
- 2026-06-18
AI Technical Summary
Existing methods for drilling cased boreholes, particularly in deep drilling, face issues with flushing channel blockages due to large debris and instability, leading to unreliable debris removal and potential pipe sticking, with existing viscosity modifiers not effectively addressed for deep hole applications.
A liquid-powered drilling apparatus with a protruding welding shoe and enlarged drilling wings that crush and grind debris, combined with a viscosity enhancer, ensures effective flushing and debris removal, maintaining a controlled annular space and using hydraulic support for the casing pipe.
The method ensures reliable debris removal without blocking the casing pipe, even at great depths, achieving flushing rates of at least 0.4 m/s with viscosity enhancers and 0.6 m/s without, effectively managing debris size and preventing pipe sticking.
Smart Images
Figure FI2025060153_18062026_PF_FP_ABST
Abstract
Description
[0001] Method and equipment for drilling a cased borehole using a liquid- powered down-the-hole drilling apparatus
[0002] The invention relates to a method for installing a casing pipe in the ground, in which method a liquid-powered drilling apparatus is used, which drilling apparatus includes at least a pilot bit and a flow channel for conducting a flushing liquid to the pilot bit and a first flushing channel for flushing out drilling debris.
[0003] The drilling rig is essentially of the type described in the publication W02010 / 043757 (Atlas Copco) with the exception of the drill bit. The method of the drilling step is also the same. Wassara AB ' s (SE) "Wassara Casing System" also represents the state of the art.
[0004] The publication US 2015 / 0330151 Al, which describes a liquid- operated drilling apparatus, is also known from the prior art. In this solution, the flushing liquid conducted along the flushing channel to in front of the pilot bit is conducted directly from in front of the pilot bit, between the reamer bit and the pilot bit, into the casing pipe attached to the pilot bit. In the situation of a blockage, the flushing debris blocks this channel between the pilot bit and the reamer bit, thus preventing the flow of flushing liquid along both this channel as well as the flushing channel to in front of the pilot bit, so that the required pressure difference cannot be generated in the drilling apparatus to activate the percussive device, i.e. the down-the-hole hammer.
[0005] In cased drilling, and especially in deep drilling, flushing channels can become blocked. Pieces of material between the pipe and the rock hole that are too large block the flushing channel and cause additional friction. Another frequent source of problems is the instability of external flushing in a deep hole. A reliable raising of material requires a flow rate of at least 0.5 m / s .
[0006] That the flowability of a material can be improved with viscosity modifiers that use polymers etc. is in itself known, but how these are to be fed into deep holes is an issue that remains unresolved.
[0007] The space between the outer diameter of the pipe to be installed and the borehole must be large enough to permit an effective external flushing upwards along the borehole.
[0008] The method builds on a down-the-hole drilling method known in itself, in which a liquid-powered drilling apparatus is used, which drilling apparatus includes at least a hammer device and a bit head, wherein the bit head includes a pilot bit and a flow channel for conducting a flushing liquid to the pilot bit and a flushing channel for further conducting the flushing liquid into the ground in front of the pilot bit, wherein drilling is carried out in the following steps:
[0009] • a welding shoe for pulling the casing pipe behind the pilot bit is attached to the casing pipe,
[0010] • a borehole is drilled into the ground using the drilling apparatus while an enlarging tool formed by drilling wings belonging to the pilot bit widen the borehole to a diameter that is greater than the outer diameter of the pilot bit for the casing pipe,
[0011] • the casing pipe is pulled behind the pilot bit during drilling,
[0012] • the borehole is flushed with a liquid flushing liquid by conducting the flushing liquid through said flow channel and said flushing channel into the ground in front of the pilot bit,
[0013] • the drilling debris produced in front of the drilling apparatus is conducted together with the flushing liquid to the outside of the casing pipe and lifted up between the borehole and the casing pipe by means of the flushing liquid,
[0014] • said pilot bit is detached from said casing pipe by turning the drilling wings belonging to the pilot bit inside the outer diameter of the pilot bit,
[0015] • said pilot bit is pulled out of the borehole,
[0016] • said casing pipe is left in the borehole.
[0017] The object of the invention is to provide a method for drilling a cased borehole in the ground by means of a drill with a liquid flushing that is more reliable than the methods of the prior art. In particular the challenges encountered in deep drilling (300- 8000 m) are overcome by means of the invention.
[0018] The characteristic features of this invention are set out in the attached patent claim 1. A further object of the invention is to provide a drilling apparatus with a liquid flushing that is better and simpler than the drilling apparatuses of the prior art.
[0019] In particular, the welding shoe according to the invention is designed so as to protrude from the casing pipe in the circumferential direction, with a structure that reduces a free space or distance a between the casing pipe and the borehole, and the reamer formed by the drilling wings is formed so as to be larger than the diameter of the welding shoe by a selected distance b, the welding shoe is configured to move axially relative to the pilot bit and thereby to press down against the reamer formed by the drilling wings, so that said reamer formed by the drilling wings and the welding shoe are configured to conjointly crush and grind drilled material through the rotation of the drilling wings and by the percussion of the hammer device, thus rendering the particle size of the material to be removed smaller than the distance (a) between the borehole and the outer diameter of the casing pipe.
[0020] An advantage of the method according to the invention is that, notwithstanding even large depths, drilling debris can be brought up reliably and does not block the casing pipe or cause the casing pipe to get stuck.
[0021] Rotary percussion drilling already crushes detached ground material remarkably well on its own. A separate crushing step is thus effective in making the ground to be flushed out even smaller.
[0022] The drilling wings are attached in an articulated manner to the drill head in such a manner that, when they are rotated in a selected direction, they open so as to form a reamer, turning radially until they reach an end position, and, when they are rotated in the opposite direction, they retract so as to become smaller than the diameter of the drill head, so that the drill head can be pulled into the casing pipe and out of the borehole.
[0023] In one advantageous application, the size of the external annular space formed by the gap between the borehole and the outer diameter of the casing pipe is limited all the way to the top and an amount of flushing liquid is determined in such a manner that a flushingagent flow rate of at least 0.4 m / s is achieved when a flushingliquid viscosity enhancer is used, while a flushing-agent flow rate of at least 0.6 m / s is achieved without one.
[0024] Said distance b is 10-80%, preferably 15-50%, of said distance a, so that flushing upwards is effective. In a preferred embodiment in which a viscosity enhancer is used, the viscosity enhancer used is a selected polymer or bentonite, which is fed through an integrated pipe inside or outside the casing pipe to the top side of the drill bit and further into the space of the gap, wherein the new feed pipe is always linked to a pipe of a smaller diameter.
[0025] In one advantageous application, the casing pipe is supported by hydraulics and / or by a winch arrangement so that the downwardacting weight of the casing pipe is lightened to a preselected range. This is particularly important in deep drilling (300-8000 m) , when the weight of even segment lengths of casing pipes becomes so great that it starts to press down on the pilot bit of its own accord .
[0026] In one advantageous application, the welding shoe includes tooth elements on its outer edge. These can be studs made of a hard alloy and / or diamond inserts.
[0027] At least one drilling wing has crushing elements on the side facing the welding shoe. The cutting angle can be equipped with studs or a bit made of a hard alloy and / or diamond inserts.
[0028] A selected polymer or bentonite, for example, is used as the viscosity enhancer. It is fed by an auxiliary feed pipe into the upper end of the casing pipe to be installed, to the top of the drill bit by an integrated pipe inside or outside the casing pipe, and onwards into the space of the gap, wherein the new feed pipe is always linked to a pipe of a smaller diameter.
[0029] The casing pipe is assembled from 10-15 m sections by welding a new section to the previous one and drilling down by the new length, wherein this process is repeated until the desired total depth is reached. The invention is described in detail in the following with reference to the attached drawings illustrating embodiments of the invention, wherein
[0030] Figure 1 shows a side view of a general arrangement of a drill rig according to the invention
[0031] Figure 2a shows a drill head with a welding shoe that has a trapezoidal form when viewed from its face side
[0032] Figure 2b shows a drill head with a bevelled welding-shoe profile in a rock-crushing position, grinding drilled material
[0033] Figure 2c shows the drill head of Figure 2b after the rock has been crushed
[0034] Figure 2d shows a drill head with a straight welding-shoe profile
[0035] Figure 3 shows a more advanced drill head
[0036] Figure 4a shows a cross section of the pilot bit, illustrating its internal channels
[0037] Figure 4b shows a cross section of a third pilot bit, illustrating its internal channels that enable an internal flushing
[0038] As shown in Figure 1, the main parts of a tracked drilling apparatus 1 according to the invention are a base machine 102, a drilling tower 104, a liquid-powered rotary device 74 and a drilling rod 76 for rotating the hammer. These are used to drill a deep cased hole in the ground. The drilling rig is constructed, for example, for a Liebherr LBR255 rig. These machines include one or two winch devices for lifting work as standard equipment. Figures 2a and 2b show the pilot bit 10 with its bit frame and wings 14. The tip 14.1 of the wing 14 enlarges the borehole 100 to a desired measurement when it is turned outwards.
[0039] In this case, an injection channel is used to feed a viscosity modifier. As can be seen from Figure 2b, the feed pipe 40 can also be inside the casing pipe.
[0040] A welding shoe 17 is welded at a bevel seam 20 to the pipe 18. A function of the upper surface of the welding shoe is thus to receive the shocks as the percussive part 302 of the drill frame pounds it downwards (Figure 4a) .
[0041] Figure 2a shows a version with three wings. In Figure 2a, one wing has been omitted, a second wing 14 is inside and a third is outside, as seen in Figure 2b. The rotary and percussive action detaches material from the ground, which is ground by the structure according to the invention.
[0042] The essential difference vis-a-vis the prior art is the protruding shape of the welding shoe 17. In the version shown in Figure 2a, the welding shoe has a trapezoidal design. Its outer circumference protrudes clearly beyond the diameter of the casing pipe 18 and has teeth 35 or analogous milling shapes formed in it. The milling occurs through the combined action of the tip 14.1 of the drillhead wing 14 and the welding shoe 17.
[0043] The more advanced drill head shown in Figure 3 has three wings 14, the respective surfaces of which include parts made of a hard alloy. The special design of the welding shoe 17 with its teeth 35 is clearly visible. The teeth 35 protrude radially from the outer surface of the casing pipe 18, while the drill-head wings 14, when rotated fully outwards, protrude radially even further than the teeth 35.
[0044] Figure 4a shows the drill head, the bottom of the drill pile and one side of the borehole. This figure shows, by way of example, the channels involved in the flushing, with a supply channel 165 in the centre of the frame. This channel splits into main channels 16 and auxiliary channels 15, the outlets of which are in the end surface of the frame. The main channels 16 lead to axial channels 161 located at the surface of the frame 30, which conduct most of the flushing liquid underneath and to the sides of the drill head. In Figure 4a, the flow discharging from the flushing channels 16 is indicated by arrows. The flushing flow rushes through the gap b between the casing pipe and the borehole to raise the drilled and ground material upwards.
[0045] From this position, the bit can be pulled away from the hole, i.e. back into the pipe.
[0046] The dashed lines indicate the turned-out position of the drilling wings 14, in which the tip 14.1 of the wing protrudes beyond the welding shoe by a distance b, thereby forming the surface of the borehole 100. This surface is at a distance a from the outer surface of the casing pipe 18.
[0047] The hammer has an actuator that oscillates in a known manner and a bit head.
[0048] The drilling equipment is mainly conventional and includes a winch arrangement for handling the casing pipe and other equipment. In Figure 1, the top of the tower includes a pulley through which a winch cable is pulled. This is attached to the operating mechanism of a top clamping device, with which it is moved into a new casing pipe to be installed on top of the previous one as drilling progresses .
[0049] The pressure of the fluid can be used to lubricate the parts of the hammer, to flush the hole and to flush debris out of the hammer. The rotary device can be driven by an electric motor. The installation pipe is usually pulled behind the drill rod into the hole. In the drilling apparatus shown in Figure 1, the rotary device 70 rotates the drill rod 76, which in turn rotates the main frame of the hammer, which in turn rotates the drill bit while the actuator of the hammer also causes a reciprocating motion of the drill bit .
[0050] Figure 4a also shows an embodiment in which the welding shoe 17 includes an extension 35 that allows an injection channel 33 attached to the outer surface of the casing pipe 18 to be pulled into the borehole together with the casing pipe 18. The extension 35 prevents ground material from entering the injection channel 33. With an extension part, the welding shoe can be twice as thick as a conventional welding shoe, thus protruding at least by the wall thickness of the casing pipe beyond the outer diameter of the casing pipe 18.
[0051] Figure 4b shows a third pilot bit with the wings 14 in the open position. The welding shoe 17 is shown here without the casing pipe. Internal channels enable an internal flushing of a blockage. Under normal circumstances, an external flushing requires most of the flow to be guided to the outside of the casing pipe.
Claims
CLAIMS1. A method for drilling a cased borehole (100) using a liquid-powered down-the-hole drilling apparatus, in which method a liquid-powered drilling apparatus is used, which drilling apparatus includes at least a hammer device and a bit head (30) , wherein the bit head (30) includes a pilot bit (10) and a flow channel (165) for conducting a flushing liquid to the pilot bit (10) and a flushing channel (16) for further conducting the flushing liquid into the ground in front of the pilot bit, wherein drilling is carried out in the following steps:• a welding shoe (17) for pulling the casing pipe (18) behind the pilot bit (10) is attached to the casing pipe (18) ,• a borehole (100) is drilled into the ground (20) using the drilling apparatus while a reamer formed by drilling wings (14) belonging to the pilot bit (10) widen the borehole (100) to a diameter that is greater than the outer diameter of the pilot bit (10) for the casing pipe (18) ,• the casing pipe (18) is pulled behind the pilot bit (10) during drilling,• the borehole (100) is flushed with a liquid flushing liquid by conducting the flushing liquid through said flow channel (165) and said flushing channel (161) into the ground (20) in front of the pilot bit (10) ,• the drilling debris produced in front of the drilling apparatus is conducted together with the flushing liquid to the outside of the casing pipe (18) and lifted up between the borehole (100) and the casing pipe (18) by means of the flushing liquid,• said pilot bit (10) is detached from said casing pipe (18) by turning the drilling wings (14) belonging to the pilot bit (10) inside the outer diameter of the pilot bit (10) ,• said pilot bit (10) is pulled out of the borehole (100) ,• said casing pipe (18) is left in the borehole (100) , characterized in that the welding shoe (17) is designed so as to protrude radially from the casing pipe (18) , with a structure that reduces a free space or distance a between the casing pipe (18) and the borehole, and the reamer formed by the drilling wings (14) is formed so as to be larger than the diameter of the welding shoe (17) by a selected distance b, and the pilot bit (10) moves axially relative to the welding shoe (17) (10) , which, where necessary, presses down against the reamer formed by the drilling wings (14) , so that said reamer formed by the drilling wings (14) and the welding shoe (17) crush and grind drilled material through the rotation of the drilling wings and by the percussion of the hammer device, thus rendering the particle size of the material to be removed smaller than the distance a between the borehole (100) and the outer diameter of the casing pipe (18) .
2. A method according to claim 1, characterized in that the size of the external annular space formed by the gap between the borehole (100) and the outer diameter of thecasing pipe (18) is limited all the way to the top and an amount of flushing liquid is determined in such a manner that a flushing-agent flow rate of at least 0.4 m / s is achieved when a flushing-fluid viscosity enhancer is used, while a flushing-agent flow rate of at least 0.6 m / s is achieved without one.
3. A method according to claim 2 or 3 in which a viscosity enhancer is used, characterized in that the viscosity enhancer used is a selected polymer or bentonite, which is fed through an integrated pipe (40) inside or outside the casing pipe (18) to the top side of the drill bit and further into the space of the gap, wherein the new feed pipe is always linked to a pipe of a smaller diameter.
4. A method according to any of claims 1 - 3, characterized in that the casing pipe (18) is supported by hydraulics and / or by a winch arrangement so that the downward-acting weight of the casing pipe (18) is lightened to a preselected range .
5. A method according to any of claims 1 - 4, characterized in that said distance b is 10-80%, preferably 15-50%, of said distance a.
6. A method according to any of claims 1 - 5, characterized in that the welding shoe (17) includes tooth elements (35) on its outer edge.
7. A method according to any of claims 1 - 6, characterized in that at least one drilling wing has crushing elements on the side facing the welding shoe.
8. A down-the-hole cased drilling rig with a liquid flushing, which includes at least a hammer device and a bit head (30) , wherein the bit head (30) includes a pilot bit (10) and a flow channel (165) for conducting a flushing liquid to the pilot bit (10) and a flushing channel (16) for flushing out drilling debris, and wherein the drilling apparatus includes a casing pipe (18) equipped with a welding shoe (17) and configured to be pulled behind the pilot bit (10) , and wherein the pilot bit includes a reamer formed by drilling wings (14) for widening the borehole (100) to a diameter that is greater than the outer diameter of the pilot bit (10) for the casing pipe (18) when the pilot bit is rotated in a selected direction at the lower end of the casing pipe, and said pilot bit (10) is detached from said casing pipe (18) by turning the drilling wings (14) belonging to the pilot bit (10) inside the outer diameter of the pilot bit (10) , characterized in that the welding shoe (17) is designed so as to protrude from the casing pipe (18) in the circumferential direction, and includes a structure that reduces a free space a between the casing pipe (18) and the borehole, and the reamer formed by the drilling wings (14) is formed so as to be larger than the diameter of the welding shoe (17) by a selected distance b, the welding shoe (17) is configured to move axially relative to the pilot bit (10) and thereby to press down against the reamer formed by the drilling wings (14) , whereby crushing elements are formed for crushing rocksthat end up between them and for grinding the material to a size smaller than said distance b.
9. A down-the-hole drilling rig according to claim 8, characterized in that the welding shoe (17) includes tooth elements (35) on its outer edge.
10. A down-the-hole drilling rig according to claim 9, characterized in that at least some of said tooth elements (35) are parts made of a hard alloy.
11. A down-the-hole drilling rig according to claim 9, characterized in that at least some of said teeth elements include diamond inserts.
12. A down-the-hole drilling rig according to any of claims 8 - 11, characterized in that said distance b is 10- 80%, preferably 15-50%, of said distance a.
13. A down-the-hole drilling rig according to any of claims 8 - 12, characterized in that the drilling wings (14) are attached in an articulated manner to the drill head (10) in such a manner that, when they are rotated in a selected direction, they open so as to form a reamer, turning radially until they reach an end position, and, when they are rotated in the opposite direction, they retract so as to become smaller than the diameter of the drill head (10) .
14. A down-the-hole drilling rig according to any of claims 8 - 9, characterized in that it includes a lightening drilling rig for supporting the casing pipe at least partially.
15. A down-the-hole drilling rig according to any of claims 8 - 9, characterized in that the welding shoe (17 ' ) is configured with its extension (35) to protect an injection pipe (33) installed on the outer surface of the casing pipe (18) .