CH701488A1 - Drill pipe for drilling device, has torsion rigid pipe body with coupling parts for connecting to adjacent drill pipe - Google Patents

Abstract

The drill pipe (1) has a torsion rigid pipe body (3) with coupling parts (5a,5b) for connecting to adjacent drill pipe. The pipe body is made of a fiber-composite-plastic. The smallest bending radius is smaller than 1 meter. The smallest bending radius is obtained by elastic deformation of the pipe bore by spreading a bending moment. An independent claim is also included for a method for manufacturing a drill pipe.

Description

The invention relates to a drill pipe for a drilling device which is designed for carrying out horizontal bores, according to the preamble of patent claim 1.

For laying cables in the ground today increasingly trenchless techniques are used. Compared to the conventional excavation of trenches, no landscape damage occurs. Buildings, railway lines, roads, waters or other obstacles are undercut or bypassed by a controllable drill head or drill bit of a so-called horizontal drilling rig. The drill head is arranged at the front end of a drill pipe. This includes a plurality of screwed by means of threaded couplings boring bars or drill pipes. The rear end of the drill string is driven by a drilling machine attached to a frame, the drill rotation corresponding to the tightening rotation of the drill rod threads. The drive of the drill bit is usually carried out pneumatically, wherein fed by a compressor at the rear end of the drill pipe compressed air in the screwed together drill pipes and guided to the drill bit. When drilling in a compressible or compressible medium such as. Soil, sandstone or sea crayon drilling devices can be used, which merely displace the medium when driving the drill head. Such drilling devices are usually designed for dry drilling without rinsing liquid. There are also other drilling devices are known in which the medium is broken through the drill head and, for example, flushed or conveyed by means of water or compressed air or other means to the outside. When propulsion of the drill string a further drill pipe is screwed at the end thereof, as soon as the preceding propulsion length corresponds to the length of a drill pipe. Conventionally, the drill pipes are made of steel and accordingly unwieldy and heavy. They each comprise at one end a threaded sleeve with an internal thread and at the other end a threaded pin with an external thread, these threads are standardized American Petroleum Institute or short API threads. It is known to form such threaded couplings directly in one piece on a pipe section or by welding, inter alia, by friction welding, to connect with the pipe section. For attaching an additional drill pipe to the drill string, the drill string may be e.g. be held on the frame of the drill by means of a fork wrench, while the additional drill pipe is screwed by the rotational movement of the drill. Conventional drill pipes made of steel have relatively large wall thicknesses and consequently relatively low free internal cross-sectional areas. They can only be slightly elastically deformed or bent. The minimum radii of curvature during drilling are on the order of about 25 m. If larger bending moments act on a steel drill pipe, then although the minimum radii of curvature can be further reduced to 15 m, the drill pipes are usually plastically deformed as well. The service lives are correspondingly low under such operating conditions. Dry bores with small borehole diameters of e.g. 5 cm can often be created in a single pass. In order to create wells with larger diameters, a pilot well is usually performed with a small hole diameter. Prior to retracting the drill string, the drill bit is replaced with a space or displacement tool. As the drill string retracts, the displacement tool expands the wellbore to the desired diameter. The direction of rotation when retracting is usually the same as for propulsion. The displacement tool can also be driven by compressed air. Drill pipes designed for dry wells and used in conjunction with drill bits that operate on the displacement principle usually have outside diameters in the range of a little less than 5 cm to about 30 cm. Drill pipes with small inner diameters cause with increasing length a relatively large pressure drop of the compressed air required to drive the drill bit. This is especially true in the field of threaded couplings, where the inner cross-section of conventional drill pipe seen in the longitudinal direction decreases abruptly.

Another disadvantage of steel drill pipes is their electrical conductivity. Electrical voltages can be easily transferred from the drill head to the drill. If the drill head accidentally encounters an electrical line while drilling, this can be life-threatening for persons in the field of drilling machines. To minimize the risk of electric shock, battery-powered warning devices are conventionally connected to the drilling device. However, these only give an audible warning signal when the drill pipe is under tension. An effective personal protection can be achieved only by means of a complex additional grounding.

For controlling the drilling direction, a locating system is used, which detects the position of the drill head, e.g. determine by magnetic properties or by radio signals of a radiosonde. If the detected actual position deviates from a predetermined desired position, a radial force is exerted on the drill head, such that the drill head remains as accurately as possible on the given path during driving. For this purpose, the drill head may be e.g. have a respect to the drilling axis asymmetrically formed wedge shape with a guide surface. During feed without rotation, the respective orientation of the guide surface determines the further course of the bore. On the other hand, during feed with rotation, the forces acting radially on the guide surface balance out on average, so that the drilling direction is rectilinear.

The object of the present invention is to provide a comparatively lightweight, easy to handle and efficient drill pipe for a drilling device. Boreholes with comparatively small radii of curvature can be created with a drill pipe composed of such drill pipes.

This object is achieved by a drill pipe according to the features of patent claim 1.

The inventive drill pipe comprises a tubular body made of a multi-layered fiber composite plastic (FRP). Compared to conventional drill pipes made of steel, the drill pipes according to the invention are significantly lighter and nevertheless have a high torsional rigidity. In addition, the bending elasticity of the inventive drill pipes is much larger than that of conventional drill pipes, so that holes with relatively small bending radii of less than 15 m can be easily performed. With specially optimized tubes of this type even bending radii of 8 m and less can be achieved, whereby the drill pipe is deformed elastically non-destructively.

To prevent or reduce the wear or the injury of fibers during drilling, the drill pipe or parts thereof may be coated with an abrasion-resistant protective layer. This is preferably renewable. Once the protective layer has worn off, a new protective layer can be applied, which significantly extends the service life of the drill pipes. The protective layer may comprise, for example, a laminate with aramid fibers which are unidirectionally wound in one or more layers. Aramid is very tough and has a high elastic energy absorption capacity. Of course, if necessary, the inner wall of the drill pipe may include such a protective layer. In particular, the innermost layer can be formed as a very thin-walled tube with good sliding properties. This facilitates in the manufacture of the drill pipes, the removal of the tubular body from the spindle of a winding machine.

The wall thicknesses of the inventive drill pipes are usually smaller than those of comparable conventional drill pipes made of steel. Accordingly, the free inner cross sections for passing compressed air for the operation of the drill bit are larger. The pressure drop in the pipe is therefore relatively small. This is especially true for drill pipes with small outside diameters of e.g. less than 60 mm as they are preferably used to make pilot holes or to drill for house connections.

By aerodynamically designed channels, the pressure drop in the coupling elements can be greatly reduced. Instead of sudden changes in the free inner cross section of the drill pipes in the region of the coupling elements as a result of paragraphs, the inventive coupling elements in the flow direction as continuously changing free inner cross sections, so that the risk of turbulence or turbulence of the funded in the drill pipe compressed air is minimal. Furthermore, the drill pipes comprise electrically insulating parts or regions, such that no electrically conductive connection between the drill head and the rear end of the drill pipe is possible. If the drill head accidentally strikes an electrical line during drilling, it protects the person from electric shock.

Compared to conventional drill pipes, the energy efficiency with the inventive drill pipes is significantly larger.

Based on some figures, the invention will be explained in more detail. Show <Tb> FIG. 1 <sep> a conventional drill pipe with a tubular body made of steel with instantly smaller inner diameters in the area of the coupling parts, <Tb> FIG. 2 <sep> a first embodiment of a streamlined drill pipe, <Tb> FIG. 3 <sep> a second embodiment of a streamlined drill pipe, <Tb> FIG. 4 is a detail view in the region of two interconnected drill pipes according to the embodiment according to FIG. 3, FIG. <Tb> FIG. 5 <sep> is a schematic representation of the tube body with differently wound fibers, <Tb> FIG. 6 <sep> is a cross section of a multilayer pipe body, <Tb> FIG. 7 <sep> a schematically illustrated, elastically bent drill string.

Fig. 1 shows a drill pipe 1, as is known from the prior art. It comprises a tubular body 3 made of steel. The outer diameter of the tubular body 3 is denoted by D1, the inner diameter by D2. At one end, a first coupling part 5a is fixedly connected to the tubular body 3, at the other end a corresponding with the first coupling part 5a second coupling part 5b. In the example shown in FIG. 1, the first coupling part 5a comprises a conical external thread and the second coupling part 5b has a corresponding internal thread according to API (American Petroleum Institute) standard. The coupling parts 5a, 5b or in general the fittings have on the side facing the tubular body 3 a connecting piece 7a, 7b, with an outer diameter adapted to the inner diameter D2 of the tubular body 3 and having a length La or Lb. These connecting pieces 7a, 7b are complete pushed or pressed from the respective ends into the tubular body 3 and connected thereto. A shoulder 9a, 9b of the coupling part 5a, 5b with a larger outer diameter D3, D4 adjoining the connection piece 7a, 7b and projecting radially therefrom bears against the respective end face of the tubular body 3. The coupling parts 5a, 5b are e.g. welded to the tubular body 3. The first coupling part 5a comprises a first channel 11a, designed as a continuous axial bore, with an inner diameter D5. At the front and / or outer end, the first coupling part 5a has an outer diameter D6 which, in accordance with the conicity of this first coupling part 5a, is smaller than the outer diameter D3 in the region of the shoulder 9a. The outer opening of the first channel 11a is thus encased by an annular outer shoulder 13a of thickness (D6-D5) / 2. The inner opening of the first channel 11a is encased in an analogous manner by an annular inner shoulder 15a of thickness (D2-D5) / 2.

The second coupling part 5b comprises a continuous axial second channel 11b, which has a constant diameter D7 in the region of the connecting piece 7b and widens in a funnel-like manner towards the outside. In this section, the conical internal thread is formed. At the outer end, the second coupling part 5b has an inner diameter D8 which, in accordance with the conicity of this second coupling part 5b, is larger than the inner diameter D7 in the region of the shoulder 9b. The outer opening of the second channel 11b is thus encased by an annular outer shoulder 13b of thickness (D4-D8) / 2. The inner opening of the second channel 11b is encased in an analogous manner by an annular inner shoulder 15b of thickness (D2 -D7) / 2.

When assembled to drill rods conventional drill pipes paragraphs 13a, 15a, 13b, 15b and abruptly changing and. small internal diameters in the passage of compressed air cause turbulence and relatively high pressure losses.

Fig. 2 shows a drill pipe 1 according to the invention, in which the coupling parts 5a, 5b are formed aerodynamically. In contrast to the conventional embodiment according to FIG. 1, the flow cross-sections of the two channels 11a, 11b extend continuously in the area of the connecting pieces 7a, 7b, so that turbulences and pressure losses do not occur when air flows through.

In the region of the tube body 3 facing ends of the connecting pieces 7a, 7b, the inner diameter D5, D7 are only slightly smaller than the inner diameter D2 of the tubular body 3. The directed towards the tubular body 3 inner shoulders 15a, 15b are so small that they affect the flow only insignificantly. These paragraphs 15a, 15b may also be rounded (no representation). Alternatively, the end portions of the tubular body 3 may have a slightly larger inner diameter D2 than the remaining inner diameter D2 over a length corresponding to the length La or Lb of the connecting pieces 7a or 7b (possibly plus a slight clearance), as shown in FIG Is shown. The connecting pieces 7a, 7b have equally enlarged outer diameter. The frontal shoulders 15a, 15b of the connecting piece 7a, 7b close in this embodiment flush against the inner wall of the remaining tubular body 3.

In an analogous manner, a shoulder is formed at the second coupling part 5b in the transition region between the connecting piece 7b and the region with the conical internal thread, which corresponds to the shoulder 15a at the front end of the first coupling part 5a. This allows the flush connection of the first coupling part 5a of another drill pipe 1. Within the second connecting piece 7b, the inner diameter of the larger value D7 tapers at the front, the tube body 3 end facing continuously to a smaller value D7 at the rear end. Subsequently, the inner diameter expands suddenly to the value D7 at the front end of the section with the conical internal thread. The width of the annular shoulder thus formed corresponds to that of the shoulder 13a at the front end of the first coupling part 5a, so that the inner cross sections of two interconnected drill pipes 1 are flush with each other. 4 shows an enlarged detail in the region of the connection point of two interconnected drill pipes 1 according to the embodiment according to FIG. 3. Between the front-side front shoulder 13a at the front end of a drill pipe 1 and the opposite annular shoulder of the other drill pipe 1 remains in the coupled state a narrower Gap 17. This ensures the proper frictional connection of the drill pipes 1 by means of the threaded coupling parts 5a, 5b. Optionally, this gap 17 can be filled by inserting a resiliently compressible loose or on one of the coupling parts 5a, 5b attached sealing ring (not shown). This causes a further improvement of the pressure tightness of the drill pipes. 1

In addition to the embodiments shown by way of example, the invention also includes drill pipes 1 with differently configured coupling parts 5a, 5b, in which the internal cross section widens as continuously as possible within the coupling parts 5a, 5b towards the tubular body 3. The widening can extend over the entire length of the coupling parts 5a, 5b or only over one or more sections of these coupling parts 5a, 5b. The radial expansion of the inner cross section may include one or more linear and / or - as shown in FIGS. 2, 3 and 4 - formed in any streamlined shape sections. At the very least, the transitions between the different inside diameters should not only each have a single erratic paragraph.

Fig. 5 shows in principle the structure of a tubular body 3 made of composite fiber plastic. In such drill pipes 1 are fibers 19a of a first fiber type with a high elastic modulus such. Carbon fibers at a pitch angle α1 of less than 60 ° in absolute value, preferably about 45 °, and fibers 19b of a second fiber type with a lower modulus of elasticity such as. Glass fibers at a pitch angle α2von amount greater than 60 °, preferably between about 75 ° and -85 °, embedded in a matrix 21 made of a resin and wound into a tubular body 3. The fibers 19a, 19b are wound unidirectionally and densely or with a very small mutual spacing in a plurality of layers. For better clarity, only a few fibers 19a, 19b are shown in FIG. 5, in which the pitch angle α1 of the first fibers 19a is approximately 45 ° and -45 ° and the pitch angle α2 of the second fibers 19b is approximately 25 ° and -25 °.

Fig. 6 shows schematically a cross-section of the tubular body 3, in which an inner first layer 23 is covered with glass fibers of a second layer 25 with carbon fibers. The second layer 25 in turn is covered by a third layer 27 of glass fibers. The outermost layer 29 is formed as a protective layer with laminated aramid fibers. The glass fiber and carbon fiber layers 23, 25, 2.7 each comprise a plurality of e.g. two to e.g. 50 layers of these fibers 19a, 19b. The orientation of the fibers in each of the individual layers 23, 25, 27 may be the same or different from layer to layer. This also applies to the protective layer of aramid fibers. Alternatively, the protective layer could also be formed in another way. As the material for the matrix 21, a thermosetting epoxy resin is preferably used. In addition to the outermost layer 29 may also be formed on the inside of the tubular body 3, a protective layer (not shown).

The tubular body 3 may be cylindrical or slightly conical. The latter facilitates the removal of the tubular body 3 from a spindle after its manufacture. In particular, it is possible to wind the fibers on a very thin-walled core tube, which remains after completion as an inner protective layer in the tubular body 3 (not shown).

The second layer 25 with the carbon fibers is electrically conductive. It is electrically insulated inside and outside by the glass fiber layers 23, 27. The coupling parts 5a, 5b are preferably adhesively bonded to the ends of the tubular body 3. You can e.g. be made of steel or other metal and are electrically isolated from the conductive carbon fiber fibers of the tubular body 3. As insulation, e.g. the glass fiber and / or protective layers are used. Alternatively or additionally, the pipe ends and / or the coupling parts 5a, 5b can be electrically insulated by additional, unspecified means here. Instead of metal, the coupling parts 5a, 5b can be made of other materials, in particular of an electrically insulating material, such as the tubular body 3 made of a fiber composite material or a ceramic material.

To improve the connection of the coupling parts 5a, 5b with the tubular body 3, the connecting pieces 7a, 7b may be attached to the outside, e.g. Ridges and on the inner sides of the tubular body 3 therewith corresponding grooves may be formed (not shown). As a result, in particular a form-locking rotation of the coupling parts 5a, 5b can be achieved. The outer diameter of the connecting pieces 7a, 7b are at least in the region of the pipe body 3 facing ends slightly smaller than in the region of the shoulders 9a, 9b. This can e.g. be achieved by a continuous linear or curved reduction of the outer diameter of the connecting pieces 7a, 7b between the shoulders 9a, 9b and the inner shoulders 15a, 15b or by chamfering the connecting pieces 7a, 7b in the region of paragraphs 15a, 15b. This prevents that the pipe body 3 or parts thereof during bending of the drill pipes 1 could be injured by edges of the connecting pieces 7a, 7b. In addition, the thickness of the adhesive layer, which increases in accordance with the ends of the connecting pieces 7a, 7b, acts as damping means between the connecting pieces 7a, 7b and the tubular body 3.

The tubular body 3 of the inventive drill pipes 1 can be manufactured in different dimensions. Typically, the lengths L are on the order of about 50 cm to about 150 cm, for example about 80 cm. The outer diameter of the tubular body 3 preferably correspond to the outer diameter D4 of the second coupling parts 5b. But they can also be smaller, in which case the second coupling parts 5b project radially beyond the tubular body 3. In the preferred small outside diameters of the tubular body 3 in the range of about 2.5 cm to about 6 cm, the thin wall thickness compared to steel pipes is particularly advantageous. The inventive drill pipes 1 have in comparison to steel tubes despite sufficient torsional stiffness a smaller weight and a significantly higher bending elasticity.

Fig. 7 shows schematically a composite of a plurality of drill pipes 1 section of a drill string, which is elastically deformed under the influence of a bending moment at least approximately to a circular arc with bending radius R. The smallest possible bending radius Rmin under which the drill string can be deformed elastically without destruction depends on various factors such as material, type and arrangement of the fibers 19a, 19b in the tubular bodies 3, outer diameter and wall thickness of the tubular body 3, material of the matrix 21 into which the Fibers 19a, 19b are embedded, etc. from. In a tube body 3, which has an inner diameter D2 of 45 mm and a wall thickness of 6 mm with a three- or four-layer structure according to FIG. 6, for example, minimum bending radii Rmin of about 8 m can be achieved.

As an alternative to coupling parts 5a, 5b according to the API standard, the coupling parts 5a, 5b may be formed as desired, provided that they allow a reliable positive and / or non-positive connection of the drill pipes 1. In particular, the connections can be designed such that the drill pipe can also be rotated in opposite directions of rotation without thereby breaking the connection.

Claims (10)

A drill pipe (1) for a drilling device adapted to carry out horizontal bores, comprising a torsionally rigid pipe body (3) having complementary coupling parts (5a, 5b) formed at the two ends for connecting adjacent drill pipes (1) to a drill string characterized in that the tubular body (3) is made of a fiber-composite plastic, and that the smallest bending radius Rmin, which can be achieved by elastic deformation of the drill pipe (1) when applying a bending moment Mbieg, is smaller than 15 m. 2. drill pipe (1) according to claim 1, characterized in that the tubular body (3) has a multilayer structure, wherein to increase the torsional stiffness fibers of a first fiber type with a high elastic modulus in the direction of the fibers of about 100 kN / mm <2> at a pitch angle α which is in the order of magnitude of 30 ° to 60 °, and wherein to ensure sufficient flexibility, fibers of a second fiber type with a lower modulus of elasticity compared to the first fiber type are used under a larger pitch angle α. of more than 60 °, and that the fibers are embedded in a plastic matrix (21). 3. drill pipe (1) according to one of claims 1 or 2, characterized in that the tubular body (3) has at least on its outer side an abrasion-resistant protective layer. 4. drill pipe (1) according to one of claims 1 to 3, characterized in that each of the coupling parts (5a, 5b) comprises a flow-shaped flow channel (11a, 11b), such that the pressure drop of the drill pipe (1) flowing through the fluid in this flow channel (11a, 11b) is low. 5. drill pipe (1) according to one of claims 1 to 4, characterized in that the complementary coupling parts (5a, 5b) are formed so that the transition region of the flow channels (11a, 11b) of two interconnected drill pipes (1) is designed aerodynamically , 6. drill pipe (1) according to one of claims 1 to 5, characterized in that the complementary coupling parts (5a, 5b) are formed and connected to the tubular body (3) that the transition areas between the tubular body (3) and the coupling parts (5a, 5b) are formed aerodynamically. 7. drill pipe (1) according to one of claims 1 to 6, characterized in that electrically insulating safety elements are provided which the power line through the tubular body (3) in the axial direction from the first coupling part (5a) to the second coupling part (5b) and vice versa and prevent in the radial direction from the inside to the outside and vice versa. 8. drill pipe (1) according to one of claims 1 to 7, characterized in that the coupling parts (5a, 5b) are glued to the tubular body (3). 9. drill pipe (1) according to one of claims 1 to 8, characterized in that the coupling parts (5a, 5b) are formed and connected to the tubular body (3), that the tubular body (3) during bending not by edges of these coupling parts (5a, 5b) is vulnerable. 10. drill pipe (1) according to one of claims 1 to 9, characterized in that the mutually corresponding coupling parts (5a, 5b) of two drill pipes (1) are tightly connected to each other.