EP0486751A1 - Directional drill string with an integrated electrical generator - Google Patents

Abstract

In a directional drill rod having its own electrical power supply from an integrated generator (29), whose stator (30) is integrated in a stationary outer tube (2, 25), while the rotor (30) surrounds a concentrically inner drilling shaft, the invention is characterised by a brushless three-phase synchronous generator whose stator has two axial windings (33, 34) which are arranged axially one behind the other and have their own connecting leads (37, 38), of which one connecting lead is used for the power supply of an electro-hydraulic pressure generator (19, 20) and the drives (15, 20) of the directional controller, while the connecting lead of the other stator winding carries the power supply for the control electronics, the excess power of the generator (29) being destroyed electronically. <IMAGE>

Description

The invention relates to a target boring bar with its own electrical energy supply through a built-in generator according to the preamble of claim 1.

The target boring bar according to the invention is set up to control rotating bores and in particular bores according to the rotary deep drilling method generally vertically downwards, but possibly also vertically upwards and then without liquid borehole flushing, so that they do not deviate from the predefined vertical drilling direction. In general, such a target boring bar forms a drill pipe, which is usually installed as the last drill pipe in front of the drill bit in the drill string, so that the front shaft end has the usual receptacle for the drilling tool, usually a drill bit. With the help of hydraulic drives, corrective moments are exerted on the drilling tool during drilling, which cancel out the forces that deflect the drilling tool and thus the drilling from the drilling direction. In the practical implementation of such a target boring bar, an outer tube concentrically surrounding the drilling shaft carries the mechanics of the target device on its jacket. This usually consists of aiming bars, each of which is articulated at 90 ° to one another at one end and is attached to one another Support the hydraulically operated plunger. Since the outer tube is stationary during drilling, the strips can be supported on the borehole joint and slide in the drilling axis during drilling, the plungers transmitting their reaction moments as correction forces to the drilling shaft and thus to the drilling tool.

This basic structure of the target boring bar according to the invention requires built-in working hydraulics for the actuation of the plunger and a controlled system, the controlled variable of which is the predefined drilling direction, the control deviation caused by disturbing variables being determined in most cases as an angle between the perpendicular and the drilling shaft axis and in a manipulated variable is converted, which mostly supplies the plunger cylinders with the hydraulic working medium via electromagnetic directional control valves. The electrical power supply of the target boring bar according to the invention by the built-in generator provides, among other things. the electrical energy required for the manipulated variable and the electro-hydraulic pressure generator.

Whereas in the case of target boring bars with a low drilling depth and correspondingly low requirements for compliance with the controlled variable, an electrical controlled system can be used, in which the control deviation is already mapped as an electrical signal, target boring bars with significantly higher requirements for compliance with the controlled variable can only be carried out with an electronic controlled system . Here, a pulse based on the interaction of electrons reflects the control deviation, which is due to filtering out the vibrations of the drill pipe and the temperature influences corrected signal a window discriminator. In the form of a three-point control, small control deviations in the order of magnitude of angular minutes are detected and converted into electrical signals for the described directional control valves of the plunger pistons via output stages of the electronic controlled system. The electrical power required for this is also supplied by the generator in the target boring bar according to the invention, so that in all cases there is no cable connection from the target boring bar to the surface.

The invention relates in particular to target boring bars which are suitable in this way for extremely deep bores which can reach 14,000 m and more, for example. In these depths, on the one hand, a high pressure load on the target boring bar due to the hydrostatic pressure of the rising borehole mud, but on the other hand also high temperatures, which are caused by the geothermal depth level. Then the pressure and temperature loads must also be taken into account when housing the electrical power supply, which, however, cannot be carried out independently of other assemblies which are important for the functioning of the target boring bar. The invention is based on this problem.

A target boring bar is known which has its own, ie built-in electrical energy supply by means of a direct current generator, the stator windings of which are built into the standing outer tube, which carries the described mechanism of the target device on its outer jacket.

The rotor of the generator, on the other hand, sits on the drilling shaft and has slip rings on which the current is drawn (EP-A-88 10 06 57). The controlled system is designed electrically. A pressure equalization with the drilling fluid is attempted in that the bearing lubrication of the drilling shaft in the standing outer tube is carried out with the fluid by means of a second partial flow branched off from the descending and cleaned drilling fluid.

The known target boring bar is unsuitable for high demands on target accuracy, because the control deviation shown in electrical signals causes the plunger to react too late. The bearing lubrication described with the descending borehole flushing is unsuitable for the slip rings because they become soiled and because, among other things, Particles can also be contained in the cleaned borehole mud, which impair the current draw from the slip rings. If such a target boring bar is subjected to considerable pressures and temperatures, there are changes in shape which can lead to mechanical as well as electrical faults. In particular, it has been found that in the winding heads of the stator the coatings have pores through which water can enter under such conditions and cause short circuits. It is also problematic that the electrical power of the direct current motor is not reduced evenly, so that excess power arises which is ultimately converted into heat in the target boring bar, which likewise leads to the occurrence of disturbance variables.

The invention is based on the object to combat different disturbances in the impairment of drilling operations, in particular in the extremely deep drilling described above.

The invention solves this problem with the features of claim 1. Further features of the invention are the subject of the dependent claims.

According to the invention, the disturbance variables which have hitherto occurred on the slip rings due to contamination and other impairments are avoided by a three-phase synchronous motor without a slip ring which, due to its motor technology, eliminates the excess power while largely avoiding waste heat. By executing this motor with a second winding of its stator, the electrical system can be supplied with one winding and the electronics with a second winding. On the one hand, this enables the electronics, but on the other hand provides enough energy for the electrical system, which is ensured by the separate power leads.

The invention has the advantage that it enables electronic control of the generator and the target device, which are practically independent of pressure and temperature and therefore do not react to the extreme conditions of deep drilling. In addition, electrical energy can be generated to a considerable extent independently of the electronics. It can be assumed that, under practical conditions, engine speeds of 60 to 100 min⁻¹ occur. Under such conditions, there are power densities in the generator which are used to supply the hydraulic Sufficient part of the control device that is able to cope with the extreme conditions of the deep drilling, which in particular can transmit the increased correction torques required in these cases to the drilling shaft.

With the features of claim 2, the problem is also solved, which results from the pressure and temperature effects on the gap of the generator between the rotor and stator. Here, by pressing the stator with a permanently elastic plastic compound, it is ensured that, in particular, the short-circuits that have previously occurred on the winding overhangs are avoided. Since the known permanently elastic plastic masses increase their volume under the influence of temperature, the resulting expansion in the stator housing counteracts the compressive forces acting on the recess of the outer tube from the outside and thus avoids an unfavorable deformation of the generator, although its parts are not relieved of pressure by an upcoming drilling fluid. The rotor winding is protected by the checker plate and the pressure-tight cable bushings from the stator prevent the plastic compression from escaping from the recess that contains the stator windings. Since the rotor is also divided into two half shells, assembly on the drilling shaft is greatly simplified.

A simplified embodiment of the invention is the subject of claim 3. Here, the stator windings are accommodated in their own housing in the form of a housing hollow cylinder accommodated in the outer tube recess, which cylinder is accordingly inserted as such into the recess can, after it has been sealed by bearing welding with an extremely thin inner sheet and pressed under vacuum, which can take place outside the target boring bar.

The high demands on the power density of one's own electrical energy supply on the one hand and the limited length of the outer tube receiving the mechanical, hydraulic, electrical or electronic components of the target device, its length, etc. is limited for reasons of strength, represents a problem in the housing of the generator. With the features of claim 4, this problem is eliminated. This is because the tender tube provided for this purpose allows a limited length of the outer tube, which accommodates the components of the target device described, but at the same time allows it to be used by the generator, which therefore cannot impair the target device. The tender pipe also has the advantage that the radial bearing of the outer pipe can be accommodated in it, the lubrication of which is particularly problematic with regard to the drilling depths to be overcome.

In realizing the features of claim 5, another axial-radial bearing can be used for the outer tube, which must be supported on the drilling shaft with an axial-radial bearing behind the drilling tool. For this purpose, permanent lubrication can be used while avoiding lubrication with the slurry, which interacts with the ring cylinder of the stator winding by being supported on the bearing cover of the permanent lubrication.

Fig. 1

eine Zielbohrstange gemäß der Erfindung im Längsschnitt und

Fig .2

in der Fig. 1 entsprechender, jedoch vergrößerter Teildarstellung die Unterbringung des der elektrischen und elektronischen Energieversorgung dienenden Generators.

The details, further features and other advantages of the invention result from the following description of an embodiment of the invention with reference to the figures in the drawing; show it

Fig. 1

a target boring bar according to the invention in longitudinal section and

Fig. 2

in Fig. 1 corresponding, but enlarged partial representation of the accommodation of the generator serving the electrical and electronic energy supply.

1, an outer tube (2) is rotatably mounted on a drilling shaft (1). The free end of the drilling shaft carries the usual receptacle (3) for a drilling tool, which is not shown in FIG. 1. The outer tube (2) is supported by a front axial-radial bearing (4) on the drilling shaft, which in turn is hollow-cylindrical, which results in a central channel (5) which supplies the descending flow of the drilling fluid to the drilling tool and the ascending current of the drilling fluid supplied, which discharges the cuttings detached from the drilling tool from the borehole. The outer tube (2) is further supported on the drilling shaft (1) by a further axial / radial bearing (6) at its end opposite the receptacle (3).

A special sealing arrangement (7) closes a radial gap (8), but sets the permanent lubrication of the series connected needle and ball bearings under the pressure of the external drilling fluid via an annular channel (9). Hereby the axial-radial bearing is lubricated depending on the depth, ie the lubricant is equalized against the flushing pressure.

On the end face of the end of the outer tube (2) associated with the receptacle (3), the two steel strips (12, 14) visible in FIG. 1, which are supported on the borehole wall, are articulated with the aid of horizontal joints (10, 11). Each of these strips is loaded with a pair of plungers (15, 16 or 17, 18) that can be hydraulically loaded. A three-phase motor (19) is used for the hydraulic energy supply and a hydrostatic drive (20) is wedged onto the shaft. A pressure accumulator (21) receives the hydraulic working fluid and passes it on to the plunger cylinders depending on the pressure. The parts described belong to a hydraulic working group, which makes the plunger cylinder loading independent of the borehole flushing, but has a working pressure corresponding to the hydrostatic pressure of the borehole flushing.

The hydraulic working fluid is controlled by control electronics which are accommodated on a circuit board (22) which, like the assemblies described above, is accommodated in a recess in the outer tube (2). Otherwise, the arc angle by which the control strips (12, 14) can move outwards in their joints (10, 11) is predetermined by path limiters (23, 24), which are also accommodated in recesses in the outer tube (2). The action on the plunger cylinders for the pressure of the hydraulic working fluid, which is dependent on the controlled variable, is achieved by directional control valves, not shown controlled, which are electrified in an electromagnetic version via the control electronics (22).

On the outer tube (2), a tender tube (25) is rotatably connected, as shown at (26) in Fig. 1. The tender tube is in turn supported by a radial bearing (27) on the drilling shaft (1). The axial bearing is subjected to the pressure of the drilling fluid via a sealing arrangement (26) corresponding to the sealing arrangement (7, 8), which, however, cannot reach the needle bearing, but instead puts permanent lubrication under pressure, which is released from the drilling fluid via an annular cylinder (27) is separated.

As can be seen from the illustration in FIG. 2, a generator (29) is installed in the tender tube (25) between the axial / radial bearing (6) and the radial bearing (26) of the Tenaer tube. The generator has a stator which is installed in the standing tender tube (25). The rotor (30 surrounds the drill shaft on a cylinder section which is reduced in diameter compared to the outer diameter of the drill shaft sections (31, 32) adjoining it.

The generator (29) is a three-phase synchronous generator, the stator of which consists of two windings (33, 34) arranged axially one behind the other, the winding heads of which can be seen at (35 and 36) in FIG. 2. Each of these windings (33, 34) has a pressure-tight cable bushing (37, 38), one of which has the discharge line for supplying power to the electro-hydraulic pressure generator (19, 20) for the plunger drives and the control valves assigned to them, while the other Derivation connects the relevant stator winding to the control electronics (22) or the motor electronics, which electronically destroy the excess power of the generator (29).

The stator windings (33, 34) are accommodated in a recess (39), which in turn is provided in a recess (40) in the inner cylindrical surface (41) of the outer tube (2). The recess (39) is closed with an extremely thin sheet (44) attached to the recess edges (42, 43). This creates a space that is closed to the outside. This contains a permanently elastic plastic mass with which it is pressed. As a result, the heads (35, 36) in particular lie in the permanently elastic plastic mass. You are therefore adequately protected against the ingress of moisture.

The rotor (30) is divided into two half-shells, which together surround the cylinder section of the drilling shaft (2) with reduced diameter and are thereby secured against axial displacement. The two half-shells lie in a longitudinally corrugated sheet metal jacket (45) and are held together by two clamp bands (46, 47), the ends of which are screwed together. Since the cable bushings (37, 38) are pressure-tight, their expansion into the recess (40) can be prevented regardless of the behavior of the plastic compound.

These cable bushings (37, 38) are located on the annular end faces of a hollow cylinder (48), the inner wall of which is formed by the closure plate (44) which is welded to the two cylinder heads (49, 50).

The hollow cylinder (48) is supported by a plurality of axial pins (51) arranged on a pitch circle and screwed into the cylinder head (49) on a bearing cover (52) which is designed as a ring cylinder and is provided with glands (53, 54), which one Seal the ring piston (55). The ring piston is subjected to permanent lubrication on the ring cylinder at (56) and holds the radial bearing, which in turn is supported on the axial bearing (58) via a pressure ring (57). The ring cylinder (52) is acted upon by the annular space (59) from the outside with the drilling fluid, so that the permanent lubrication of the axial / radial bearing (6) is pressure-dependent according to the drilling depth.

The cylinder (52) of the bearing cover and the hollow cylinder (48) of the stator with the two axial windings (33, 34) are in the common recess (40) on the inside of the tender tube (25) together with the axial-radial bearing (6) Drill shaft housed. Therefore, the assembly can be carried out in the axial order of the parts of the axial-radial bearing, the hollow cylinder of the two stator windings according to the rotor's montgage and the adjoining bearing parts of the tender tube.

Claims (5)

Target boring bar with its own electrical energy supply through a built-in generator (29), the stator (30) of which is installed in a standing outer tube (2, 25), while the rotor (30) surrounds a concentrically inner tubular shaft, characterized by a three-phase synchronous generator without slip rings, whose stator has two windings (33, 34) arranged axially one behind the other with their own leads (37, 38), one of which leads to the power supply of an electrohydraulic pressure generator (19, 20) and the drives (15, 20) for target control, while the Derivation of the other stator winding leads to the power supply to the control electronics, the excess power of the generator (29) being electronically destroyed. Target boring bar according to claim 1, characterized in that the stator windings (33, 34) in a common recess (39, 40) of the inner cylindrical surface (41) of the outer tube (2) in a through a cylindrical, at the recess edges (42, 43) fastened sheet metal (44) are enclosed space, which is pressed with a permanently elastic plastic mass, and that the rotor (30) divided into two half-shells in a longitudinally corrugated Sheet metal jacket (45) is housed, which is held together with screwed clamps (46, 47) at both ends, the leads (37, 38) being pressure-tight and arranged on the end faces of the recess (39). Target boring bar according to one of claims 1 or 2, characterized in that the stator recess (39) is accommodated in a hollow cylinder (48), the inner wall of which is formed by the cylindrical locking plate (44) which is laser-welded to both cylinder heads (49, 50) A cable bushing (37, 38) is sealed in each of the cylinder heads (49, 50), each of which is assigned to a derivative of the stator (33, 34). Target boring bar according to one of Claims 1 to 3, characterized in that the generator (29) is accommodated in a tender tube (25) which is connected in a rotationally fixed manner to the outer tube (2) having the mechanism of the target device, the non-rotatable connection (26) is arranged behind a rear axial-radial bearing (6) of the drilling shaft (1) and the rear end of the tender tube (25) is supported on the drilling shaft (1) with a radial bearing (26 '). Target boring bar according to one of claims 1 to 4, characterized in that the cylinder (48) of the stator (33, 34) is accommodated in a common recess (40) together with the axial-radial bearing (6) of the drilling shaft (1) and with it Cylinder head (29) is supported on a bearing cover (52) which in the common recess the receiving space of permanent lubrication the drilling shaft roller bearing (57, 58) closes.

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