Field of the invention

The invention relates to a method for surveying drill holes as defined in the preamble of independent claim 1.

The invention also relates to a drilling arrangement for percussive drilling as defined in the preamble of independent claim 20.

The invention relates also to a borehole survey assembly for use in a method for percussive drilling and/or in an arrangement for percussive drilling as defined in independent claim 36.

In drilling it is important to have information about the depth and the direction of the boreholes. For this purpose various borehole survey tools and methods are known in the art by which it is possible to obtain information about the depth and the direction of boreholes.

Publication US 8,011,447 presents a method of surveying drill holes, typically for use in underground mining situations where the holes are bored using a top hammer drill rig, utilizes a survey tool located adjacent the drill bit which is used to log position readings as the drill string is withdrawn from the hole after the drilling operation. In this manner, it is possible to log the actual hole bored by the drill string in real time as the drilling operation proceeds, and show deviation from intended hole positions. The survey tool typically includes an inertial survey package, a power source, and a data logger with the survey package selected from the group comprising commercially known inertial known survey packages, for superior characteristics of resistance to vibration and impact. The survey tool is maintained in a sleeping mode while drilling is undertaken, and activated to provide position data as the drill string is progressively withdrawn from the actual hole path.

Objective of the invention

The object of the invention is to provide a method for surveying drill holes, a drilling arrangement, and a borehole survey tool assembly.

Short description of the invention

The method for surveying drill holes of the invention is characterized by the definitions of independent claim 1.

Preferred embodiments of the method are defined in the dependent claims 2 to 19. The method comprises a first providing step for providing a drill tool comprising at least one drill rod and a drill bit assembly. The method comprises additionally a second providing step for providing a borehole survey tool comprising sensor means for measuring a borehole. The method comprises an arranging step for arranging the borehole survey tool within the drill tool. The method comprises a drilling step for drilling with the drill tool a borehole by a drilling process including at least percussive drilling. The method comprises a measuring step for measuring the borehole by means of the sensor means of the borehole survey tool to obtain data of the borehole. The method comprises a processing step for processing data of the borehole with a data processing means to obtain borehole status information. In the method, a drill tool comprising a central flushing channel for conducting flushing fluid to the drill bit assembly is used and the borehole survey tool is in the arranging step arranged in the central flushing channel so that flushing fluid can flow in the central flushing channel past the borehole survey tool. The arranging step includes preferably, but not necessarily, suspending the borehole survey tool in the central flushing channel of the drill tool between damping means. Such damping means comprises preferably, but not necessarily at least one of the following: spring means, such as conical springs, made of a wire or the like having a thickness between 0.5 and 3.0 mm, hydraulic damping means and pneumatic damping means. Such damping means can for example comprise spring means, such as conical springs, made of a wire or the like having a thickness, such as a diameter, between 0.5 and 3.0 mm, preferable between 1.0 and 2.5 mm, more preferable between 1.5 and 2.0 mm, for example 1.8 mm.

The drilling arrangement for percussive drilling of the invention is correspondingly characterized by the definitions of independent claim 20.

Preferred embodiments of the drilling arrangement are defined in the dependent claims 21 to 35.

The drilling arrangement comprises a drill tool for drilling boreholes. The drill tool comprises at least one drill rod and a drill bit assembly. The drilling arrangement comprises a borehole survey tool comprising sensor means for measuring a borehole drilled by the drill tool to obtain data of a borehole drilled by the drill tool, wherein the borehole survey tool is arranged within the drill tool. The drilling arrangement comprises data processing means for processing data of the borehole to obtain borehole status information. The drill tool comprises a central flushing channel for conducting flushing fluid to the drill bit assembly and the borehole survey tool is arranged in the central flushing channel so that fluid can flow in the central flushing channel past the borehole survey tool. The borehole survey tool is preferably, but not necessarily, suspended in the flushing channel between damping means. The damping means used in the method comprises preferably, but not necessarily at least one of the following: spring means, such as conical springs, made of a wire or the like having a thickness between 0.5 and 3.0 mm, hydraulic damping means and pneumatic damping means. The damping means used in the method can for example comprise spring means, such as conical springs, made of a wire or the like having a thickness, such as a diameter, between 0.5 and 3.0 mm, preferable between 1.0 and 2.5 mm, more preferable between 1.5 and 2.0 mm, for example 1.8 mm. The invention relates also to a borehole survey assembly for use in a method for percussive drilling and/or in an arrangement for percussive drilling as defined in claim 36.

Preferred embodiments of the borehole survey assembly are defined in the dependent claims 37 to 50.

The borehole survey assembly comprises a borehole survey tool containing sensor means for collecting data of a borehole. The borehole survey assembly comprises additionally damping means for suspending the borehole survey tool in a central flushing channel of a drill tool for percussive drilling between said damping means. Such damping means comprises preferably, but not necessarily at least one of the following: spring means, such as conical springs, made of a wire or the like having a thickness between 0.5 and 3.0 mm, hydraulic damping means and pneumatic damping means. Such damping means can for example comprise spring means, such as conical springs, made of a wire or the like having a thickness, such as a diameter, between 0.5 and 3.0 mm, preferable between 1.0 and 2.5 mm, more preferable between 1.5 and 2.0 mm, for example 1.8 mm.

A purpose of the damping means is to protect the components of the borehole survey assembly during the percussive drilling. By the components of the borehole survey assembly can be meant for example at least one gyro sensor for generating a first signal indicative of angular rate and at least one acceleration sensor for generating a second signal indicative of acceleration along a borehole drilled by the drilling arrangement or a drilling arrangement and possible a piezoelectric device for harvesting electric energy during percussive drilling.

If the borehole survey assembly is provided with a piezoelectric device for harvesting electric energy during percussive drilling, the damping means of the borehole survey assembly are preferably, but not necessarily, tuned to create a correct oscillation frequency for the piezoelectric device during the percussive drilling so that the piezoelectric device is able to harvest electrical energy during percussive drilling.

List of figures

In the following the invention will described in more detail by referring to the figures, which

Figure 1 shows a drilling arrangement,

Figure 2 shows in cut view the end of a drill tool that is provided with a borehole survey assembly,

Figure 3 shows in cut view a borehole survey assembly according to one embodiment, Figure 4 shows a first adapter part and a second adapter part which are used in some embodiments for fastening of the drill bit assembly to a drill rod of the drill tool, and figure 4 also show how a borehole survey tool can be arranged when such first adapter part and such second adapter part are used,

Figure 5 shows a borehole survey assembly according to another embodiment, Figure 6 is a detail view of one embodiment a piezoelectric device that can be used in the borehole survey assembly for harvesting electrical energy during percussive drilling, and Figure 7 is a more detailed view of the piezoelectric device shown in figure 6.

Detailed description of the invention

The invention relates to a method for surveying drill holes, to a drilling arrangement, and to a borehole survey assembly for use in the method and/or in the arrangement.

First the method for surveying drill holes and some preferred embodiments and variants of the method will be described in greater detail.

The method comprises a first providing step for providing a drill tool 1 comprising at least one drill rod 2 and a drill bit assembly 3.

The method comprises additionally a second providing step for providing a borehole survey tool 4 comprising sensor means 5 for measuring a borehole 6.

The method comprises an arranging step for arranging the borehole survey tool 4 within the drill tool 1.

The method comprises a drilling step for drilling with the drill tool 1 a borehole 6 by a drilling process including at least percussive drilling.

The method comprises a measuring step for measuring the borehole 6 by means of the sensor means 5 of the borehole survey tool 4 to obtain data of the borehole 6.

The method may comprise a sending step for sending data of the borehole 6 from the borehole survey tool 4 to a data processing means 7 and a receiving step for receiving data of the borehole 6 by the data processing means 7. A wire or wireless connection (not shown in the drawings) may be used in the sending step and the receiving step. In a preferred embodiment of the method, the method comprises a saving step for storing data of the borehole 6 on a memory means 26 of the borehole survey tool 4 when the borehole survey tool 4 together with the drill tool is located at least partly in the borehole 6. In this preferred embodiment the sending step and the receiving step is performed after that the borehole survey tool 4 has been removed from the borehole 6 by transferring data of the borehole 6 from the memory means 26 to a data processing means 7.

The method comprises a processing step for processing data of the borehole 6 with a data processing means 7 to obtain borehole status information.

In the method, a drill tool 1 comprising a central flushing channel 8 for conducting flushing fluid such as flushing liquid and/or flushing gas to the drill bit assembly 3 is used and the borehole survey tool 4 is in the arranging step releasable or fixedly arranged in the central flushing channel 8 so that flushing fluid can flow in the central flushing channel 8 past the borehole survey tool 4 in the drill tool 1.

Because the borehole survey tool 4 is in the arranging step arranged in the central flushing channel 8, the borehole survey tool 4 will be cooled by flushing fluid flowing in the central flushing channel 8 of the drill tool 1.

The method may include using a drill bit assembly 3 comprising a flushing channel section 30, and the arranging step may include arranging the borehole survey tool 4 at least partly in the flushing channel section 30 of the drill bit assembly 3.

In some embodiments of the method, the first providing step of the method comprises providing additionally an adapter 9 comprising a central flushing channel section 36. In such embodiment the arranging step includes fastening the drill bit assembly 3 to a drill rod 2 of the drill tool 1 by means of the adapter 9 so that the central flushing channel section 36 of the adapter 9 forms a part of the central flushing channel 8 of the drill tool 1. In such embodiments, the arranging step includes arranging the borehole survey tool 4 at least partly in the central flushing channel section 36 of the adapter 9.

In some embodiments of the method, the first providing step of the method comprises providing additionally an adapter 9 comprising a first adapter part 10 and a second adapter part 11, so that the first adapter part 10 comprising a first female thread 12 and a first male thread 13 for fastening a drill bit assembly 3 to the first adapter part 10 of the adapter 9, and so that the second adapter 11 part comprising a second male thread 14 for cooperation with the first female thread 12 of the first adapter part 10 and a second female thread 15 for fastening the second adapter part 11 of the adapter 9 to a drill rod 2 of the drill tool 1, and so that the first adapter part 10 comprises a first central flushing channel part 16 and the second adapter part 11 comprises a second central flushing channel part 17. In such embodiments, the arranging step includes arranging the borehole survey tool 4 at least partly in the first central flushing channel part 16 of the first adapter part 10 and/or at least partly in the second central flushing channel part 17 of the second adapter part 11 and connecting the first adapter part 10 and the second adapter part 11 by means of the a first female thread 12 of the first adapter part 10 and by means of the second male thread 14 of the second adapter part 11. Such embodiments includes a fastening step for fastening the drill bit assembly 3 to a drill rod 2 of the drill tool 1 by means of the adapter 9 so that the first central flushing channel part 16 of the first adapter part 10 and the second central flushing channel part 17 of the second adapter part 11 together forms a part of the central flushing channel 8 of the drill tool 1.

The arranging step includes preferably, but not necessarily, suspending the borehole survey tool 4 in the central flushing channel 8 of the drill tool 1 between damping means 18. One purpose of the damping means 18 are to protect the sensor means 5 and other devices in the borehole survey tool 4 during the drilling step. The damping means used in the method comp preferably, but not necessarily, at least one of the following: Spring means, such as conical springs, made of a wire or the like having a thickness between 0.5 and 3.0 mm, hydraulic damping means, and pneumatic damping means. The damping means used in the method can for example comprise spring means, such as conical springs as is shown for example in figures 4 and 5, made of a wire or the like having a thickness, such as a diameter, between 0.5 and 3.0 mm, preferable between 1.0 and 2.5 mm, more preferable between 1.5 and 2.0 mm, for example 1.8 mm. Conical springs are preferably, but not necessarily, used, because due to the construction of a conical spring, flushing fluid can more efficiently flow past a conical spring than a cylindrical spring. One reason for this is that the flow direction of the flushing fluid need to change less when flowing through a conical spring in the direction of the central of the conical spring than when flowing through a cylindrical spring in the direction of the central axis of the cylindrical spring. If spring means are used as damping means 18, two spring means are preferably, but not necessarily used, as shown for example in figure 2, so that each damping means 18 is arranged between an inner surface (not marked with a reference numeral) of the central flushing channel 8 and the borehole survey tool 4 so that the borehole survey tool 4 is suspended between the spring means.

The arranging step includes preferably, but not necessarily, suspending the borehole survey tool 4 in the central flushing channel 8 of the drill tool 1 between damping means 18 so that the damping means 18 are situated outside the borehole survey tool 4 in the central flushing channel 8 of the drill tool 1 so that the damping means 18 are exposed to flushing fluid flowing in the central flushing channel 8 of the drill tool 1 and so that the damping means 18 are in direct contact with flushing fluid flowing in the central flushing channel 8 of the drill tool 1.

In a preferred embodiment of the method, the arranging step includes suspending the borehole survey tool 4 in the central flushing channel 8 of the drill tool 1 between damping means 18 so that the borehole survey tool 4 is supported in the central flushing channel 8 of the drill tool 1 solely by means of said damping means 18. Such embodiment is especially advantageous in percussive drilling, because the sensor means 5 of the borehole survey tool 4 will be protected for example against excess vibrations.

In the second providing step of the method is preferably, but not necessarily, provided a borehole survey tool 4 having the sensor means 5 of the borehole survey tool 4 at least partly, preferably fully, embedded in polymer such as polyurethane so that the polymer at least partly embedding the sensor means 5 also at least partly, preferably fully, forms the outermost surface of the borehole survey tool 4 and such that the polymer at least partly embedding the sensor means 5 also at least partly, preferably fully, forms a protective casing 24 of the borehole survey tool 4. In such embodiment the borehole survey tool 4 will be exposed to flushing fluid flowing in the central flushing channel 8 of the drill tool 1. Because the polymer that at least partly embeds the sensor means 5 also at least party forms the outermost surface of the borehole survey tool 4, the flushing fluid flowing in the central flushing channel 8 of the drill tool 1 can effectively cool the sensor means 5 of the borehole survey tool 4.

The second providing step of the method may include providing a borehole survey tool 4 comprising at least one flushing fluid passage 20 for allowing flushing fluid to flow through the borehole survey tool 4 in the central flushing channel 8 of the drill tool 1.

The arranging step of the method may, as shown in figures 2 and 4, include forming at least one flushing fluid passage 20 for flushing fluid between the borehole survey tool 4 and the side walls (not marked with a reference numeral) of the central flushing channel 8 for allowing flushing fluid to flow past the borehole survey tool 4 in the central flushing channel 8 of the drill tool 1.

The second providing step of the method may include providing a borehole survey tool 4 comprising a piezoelectric device 19 for harvesting energy, whereby the drilling step of the method includes harvesting energy during the drilling step by means of the piezoelectric device.

The second providing step of the method may include providing a borehole survey tool 4 comprising sensor means 5 including at least one gyro sensor 31 for generating a first signal indicative of angular rate, and at least one acceleration sensor 32 for generating a second signal indicative of acceleration along the borehole 6, whereby the measuring step includes measuring angular rate with at least one gyro sensor 31 and generating a first signal indicative of angular rate and whereby the measuring step includes measuring acceleration with at least one acceleration sensor 32 and generating a second signal indicative of acceleration along the borehole 6.

The method may additionally include a presenting step for presenting borehole status generated in the processing step.

In the method, the measuring step may be performed as the drill tool 1 is withdrawn from the borehole 6. In the method, the measuring step may be performed during the drilling step. In a preferred embodiment of the method, the drilling step includes a waiting period during which the drill tool 1 is kept in the borehole 6 stationary with respect to a longitudinal direction the borehole 6 i.e. a waiting period during which the drill tool 1 is kept in the borehole 6 stationary in place with respect to the depth of the borehole 6. In this preferred embodiment of the method the measuring step is performed during the waiting period of the drilling step.

Next the drilling arrangement for percussive drilling and some preferred embodiments and variants thereof will be described in greater detail.

The drilling arrangement comprises a drill tool 1 for drilling boreholes.

The drill tool 1 comprises at least one drill rod 2 and a drill bit assembly 3.

The drilling arrangement comprises a borehole survey tool 4 comprising sensor means 5 for measuring a borehole 6 drilled by the drill tool 1 to obtain data of a borehole 6 drilled by the drill tool 1, wherein the borehole survey tool 4 is arranged within the drill tool 1.

The drilling arrangement may comprise transmitting means 23 for sending data of the borehole 6 from the borehole survey tool 4 and second receiving means 33 for receiving data of the borehole 6 sent by the transmitting means 23. A wire or wireless connection (not shown) may be provided between the transmitting means 23 and the second receiving means 33. Alternatively or additionally the borehole survey tool 4 may comprise memory means 26 for storing data of a borehole 6 on the memory means 26 of the borehole survey tool 4 when the borehole survey tool 4 together with the drill tool 1 is located at least partly in a borehole 6 so that data of the borehole 6 can later be transferred to the data processing means 7 for example by connecting the memory means 26 to the data processing means 7 after that the borehole survey tool 4 together with drill tool 1 has been removed from the borehole 6.

The drilling arrangement comprises data processing means 7 for processing data of the borehole to obtain borehole status information.

The drill tool 1 comprises a central flushing channel 8 for conducting flushing fluid such as flushing liquid and/or flushing gas to the drill bit assembly 3 and the borehole survey tool 4 is releasable or fixedly arranged in the central flushing channel 8 so that fluid can flow in the central flushing channel 8 past the borehole survey tool 4.

Because the borehole survey tool 4 is arranged in the central flushing channel 8, the borehole survey tool 4 will be cooled by flushing fluid flowing in the central flushing channel 8.

The drill bit assembly 3 may comprise a flushing channel section 30, and the borehole survey tool 4 may be arranged at least partly in the flushing channel section 30 of the drill bit assembly 3.

In some embodiments of the drilling arrangement the drill tool 1 comprise additionally an adapter 9 comprising a central flushing channel section 36. In these embodiments the drill bit assembly 3 is fastened to a drill rod 2 of the drill tool 1 by means of the adapter 9 so that the central flushing channel section 36 of the adapter 9 forms a part of the central flushing channel 8 of the drill tool 1. In these embodiments the borehole survey tool 4 is arranged at least partly located in the central flushing channel section 36 of the adapter 9.

Some embodiments of the drilling arrangement such as the drilling arrangement partly shown in figure 2 comprise an adapter 9 comprising a first adapter part 10 and a second adapter part 11. In these embodiments the first adapter part 10 comprises a first female thread 12 and a first male thread 13 for fastening a drill bit assembly 3 to the first adapter part 10 of the adapter 9. In these embodiments the second adapter part 11 comprises a second male thread 14 for cooperation with the female thread 12 of the first adapter part 10 and a second female thread 15 for fastening the second adapter part 11 of the adapter 9 to a drill rod 2 of the drill tool 1. In these embodiments the first adapter part 10 comprises a first central flushing channel part 16 and the second adapter part 11 comprises a second central flushing channel part 17. In these embodiments the borehole survey tool 4 is arranged at least partly in the first central flushing channel part 16 of the first adapter part 10 and/or at least partly in the second central flushing channel part 17 of the second adapter part 11. In these embodiment the first adapter part 10 and the second adapter part 11 are connected by means of the a first female thread 12 of the first adapter part 10 and by means of the second male thread 14 of the second adapter part 11 and the drill bit assembly 3 is connected to a drill rod 3 by means of the adapter 9 i.e. by means of the first adapter part 10 and the second adapter part 11 so that first central flushing channel part 16 of the first adapter part 10 and the second central flushing channel part 17 of the second adapter part 11 together forms a part of the central flushing channel 8 of the drill tool 1.

The borehole survey tool 4 is preferably, but not necessarily, as shown in figure 2, suspended in the central flushing channel 8 of the drill tool 1 between damping means 18. Such damping means 18 comprises preferably, but not necessarily at least one of the following: spring means, such as conical springs, made of a wire or the like having a thickness between 0.5 and 3.0 mm, hydraulic damping means, and pneumatic damping means. Such damping means can for example comprise spring means, such as conical springs, made of a wire or the like having a thickness, such as a diameter, between 0.5 and 3.0 mm, preferable between 1.0 and 2.5 mm, more preferable between 1.5 and 2.0 mm, for example 1.8 mm. One purpose of the damping means 18 are to protect the sensor means 5 in the borehole survey tool 4 during percussive drilling. Such damping means 18 comprises preferably, but not necessarily at least one spring in the form of conical springs, as shown in figures 4 and 5. Conical springs are preferably, but not necessarily, used, because due to the construction of a conical spring, flushing fluid can more efficiently flow past a conical spring than a cylindrical spring. One reason for this is that the flow direction of the flushing fluid need to change less when flowing through a conical spring in the direction of the central of the conical spring than when flowing through a cylindrical spring in the direction of the central axis of the cylindrical spring. If spring means are used as damping means 18, two spring means are preferably, but not necessarily used, as shown for example in figure 2, so that each damping means 18 is arranged between an inner surface (not marked with a reference numeral) of the central flushing channel 8 and the borehole survey tool 4 so that the borehole survey tool 4 is suspended between the spring means.

The damping means 18 are preferably, but not necessarily, situated outside the borehole survey tool 4 in the central flushing channel 8 of the drill tool 1 so that the damping means 18 are exposed to flushing fluid flowing in the central flushing channel 8 of the drill tool 1 and so that the damping means 18 are in direct contact with flushing fluid flowing in the central flushing channel 8 of the drill tool 1.

In an embodiment of the arrangement, the borehole survey tool 4 is suspended in the central flushing channel 8 of the drill tool 1 between damping means 18 so that the borehole survey tool 4 is supported in the central flushing channel 8 of the drill tool 1 solely by means of said damping means 18. Such embodiment is especially advantageous in percussive drilling, because the sensor means 5 of the borehole survey tool 4 will be protected for example against excess vibrations.

The sensor means 5 of the borehole survey tool 4 are preferably, but not necessarily, at least partly, preferably fully, embedded in polymer such as polyurethane so that the polymer at least partly embedding the sensor means 5 also at least partly, preferably fully, forms the outermost surface of the borehole survey tool 4 and so that the polymer at least partly embedding the sensor means 5 also at least partly, preferably fully, forms a protective casing 24 of the borehole survey tool 4. Because the polymer that at least partly embeds the sensor means 5 also at least party forms the outermost surface of the borehole survey tool 4, the flushing fluid flowing in the central flushing channel 8 of the drill tool 1 can effectively cool the sensor means 5 of the borehole survey tool 4.

The borehole survey tool 4 comprises preferably, but not necessarily, at least one flushing fluid passage for allowing flushing fluid to flow through the borehole survey tool 4.

The arrangement comprises preferably, but not necessarily, at least one flushing fluid passage 20 for flushing fluid between the borehole survey tool 4 and the flushing channel for allowing flushing fluid to flow past the borehole survey tool 4.

The borehole survey tool 4 comprises preferably, but not necessarily, a piezoelectric device 19 for harvesting energy during percussive drilling.

The borehole survey tool 4 comprises preferably, but not necessarily, sensor means 5 including at least one gyro sensor 31 for generating a first signal indicative of angular rate, and at least one acceleration sensor 32 for generating a second signal indicative of acceleration along the borehole 6.

The arrangement comprises preferably, but not necessarily, presenting means 34 for presenting borehole status information produced by the data processing means 7.

Next the borehole survey assembly (not marked with a reference numeral) for use in a method for percussive drilling such as in a method as described in this publication and/or in a drilling arrangement for percussive drilling such as in an arrangement as described in this publication and some preferred embodiments and variants of the borehole survey assembly will be described in greater detail.

The borehole survey assembly comprises a borehole survey tool 4 containing sensor means 5 for collecting data of a borehole 6.

The borehole survey assembly comprises additionally damping means 18 for suspending the borehole survey tool in a central flushing channel 8 of a drill tool 1 for percussive drilling between said damping means 18. Such damping means comprises preferably, but not necessarily at least one of the following: spring means, such as conical springs, made of a wire or the like having a thickness between 0.5 and 3.0 mm, hydraulic damping means and pneumatic damping means. Such damping means can for example comprise spring means, such as conical springs, made of a wire or the like having a thickness, such as a diameter, between 0.5 and 3.0 mm, preferable between 1.0 and 2.5 mm, more preferable between 1.5 and 2.0 mm, for example 1.8 mm. Conical springs are advantageous to use in the borehole survey assembly, because they have less impact on the flow of flushing fluid in the central flushing channel 8. Conical springs are preferably, but not necessarily, used, because due to the construction of a conical spring, flushing fluid can more efficiently flow past a conical spring than a cylindrical spring. One reason for this is that the flow direction of the flushing fluid need to change less when flowing through a conical spring in the direction of the central of the conical spring than when flowing through a cylindrical spring in the direction of the central axis of the cylindrical spring. If spring means are used as damping means 18, two spring means are preferably, but not necessarily used, as shown for example in figure 2, so that each damping means 18 is arranged between an inner surface (not marked with a reference numeral) of the central flushing channel 8 and the borehole survey tool 4 so that the borehole survey tool 4 is suspended between the spring means.

The damping means 18 are preferably, but not necessarily, situated outside the borehole survey tool 4.

The sensor means 5 of the borehole survey tool 4 are preferably, but not necessarily, at least partly, preferably fully, embedded in polymer such as polyurethane so that the polymer at least partly embedding the sensor means 5 also at least partly, preferably fully, forms the outermost surface of the borehole survey tool 4 and so that the polymer at least partly embedding the sensor means 5 also at least partly forms a protective casing 24 of the borehole survey tool 4. Because the polymer that at least partly embeds the sensor means 5 also at least party forms the outermost surface of the borehole survey tool 4, the flushing fluid flowing in the central flushing channel 8 of the drill tool 1 can effectively cool the sensor means 5 of the borehole survey tool 4.

Because the borehole survey tool 4 is to be suspended in a central flushing channel 8 of a drill tool 1, the borehole survey tool 4 will be cooled by flushing fluid flowing in the central flushing channel 8.

In the embodiment shown in figures 2 to 5, the borehole survey tool 4 has an elongated configuration having two opposite ends, and one damping means 18 at each opposite end.

The borehole survey assembly comprises preferably, but not necessarily, a piezoelectric device 19 for harvesting energy during percussive drilling i.e. when the drill tool 1 and the components thereof (the drill rod(s) 2 and the drill bit assembly 3 and a possible adapter 9 between a drill rod 2 and the drill bit assembly 3) oscillates during percussive drilling. The borehole survey assembly comprises preferably, but not necessarily also energy storing means 21 for storing electrical energy produced by the piezoelectric device 19. Especially if surveying of the borehole 6 is performed as the drill tool 1 is withdrawn from the borehole, energy storing means 21 are of advantage, because this enables harvesting energy during percussive drilling by means of the piezoelectric device 19 when the borehole 6 is drilled and subsequently using the energy stored on the energy storing means 21 for the sensor means afterwards when the drill tool 1 is withdrawn from the borehole 6. The piezoelectric device 19 may comprise one or more piezoelectric apparatuses that may be of Unimorph-, Bimorph-, Monomorph-, or Multimorph-type. A such piezoelectric apparatus may be pre-strained and may be made for example of metal, polymer and/or ceramic material. A such piezoelectric apparatus may for example, as shown in figures 6 and 7, comprise a flexible piezoelectric plate 35 that is fastened at one end or both ends to the borehole survey tool 4. A mass 36 for manually adjusting the resonation frequency may be fastened to the flexible piezoelectric plate. The mass 36 is preferably, but not necessarily, arranged eccentrically so that the mass 26 will move both as a result of rotation of the drill tool 1 and as a result of the oscillation of the drill tool 1. A coil (not shown in the figures) or a capacitor (not shown in the figures) may be provided for electrically adjusting the resonation frequency.

The energy storing means 21 for storing energy may comprise an accumulator 28 for storing energy and an inductive coil 29 for charging the accumulator 28, or a capacitor.

The sensor means 5 of the borehole survey assembly comprises preferably, but not necessarily, at least one gyro sensor 31 for generating a first signal indicative of angular rate, and at least one acceleration sensor 32 for generating a second signal indicative of acceleration along the borehole 6.

The borehole survey assembly comprises preferably, but not necessarily, first receiving means 22 for receiving control signals to control the operation of the borehole survey assembly.

The borehole survey assembly comprises preferably, but not necessarily, transmitting means 23 for transmitting data of a borehole 6.

The borehole survey assembly comprises preferably, but not necessarily, a protective casing 24, for example a polymer casing. A such protective casing is preferably but, not necessarily, dust- and watertight.

The borehole survey assembly comprises preferably, but not necessarily, holding means 27 for preventing the borehole survey assembly from rotating when mounted in a central flushing channel 8 of a drill tool 1.

The borehole survey assembly comprises preferably, but not necessarily, a control means 25 for controlling the sensor means 5.

The borehole survey assembly comprises preferably, but not necessarily, memory means 26 for storing data of the borehole 6 produced by the sensor means 5 when the borehole survey assembly together with the drill tool 1 is located at least partly in a borehole 6.

It is apparent to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.

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14

List of reference numerals

1. Drill tool

2. Drill rod

3. Drill bit assembly

4. Borehole survey tool

5. Sensor means

6. Borehole

7. Data processing means

8. Central flushing channel

9. Adapter

10. First adapter part

11. Second adapter part

12. First female thread

13. First male thread

14. Second male thread

15. Second female thread

16. First central flushing channel part

17. Second flushing channel part

18. Damping means

19. Piezoelectric device

20. Flushing fluid passage

21. Energy storing means

22. First receiving means

23. Transmitting means

24. Protective casing

25. Control means

26. Memory means

27. Holding means

28. Accumulator

29. Inductive coil

30. Flushing channel section

31. Gyro sensor

32. Acceleration sensor

33. Second receiving means

34. Display means

35. Flexible piezoelectric plate

36. Mass

37. Central flushing channel section