WO2025254574A1

WO2025254574A1 - Method and arrangement for conditioning a drill bit during a rotary core drilling process into rock

Info

Publication number: WO2025254574A1
Application number: PCT/SE2024/050549
Authority: WO
Inventors: Robert DIMBERG; Marcus LÖFGREN; Michael Krasser; Göran LARBO; Krister Larsson
Original assignee: Epiroc Rock Drills AB
Current assignee: Epiroc Rock Drills AB
Priority date: 2024-06-04
Filing date: 2024-06-04
Publication date: 2025-12-11
Anticipated expiration: 2026-12-04

Abstract

The present disclosure relates to a computer-implemented method for conditioning a drill bit during a rotary core drilling process into rock, which drilling process is performed by a drill rig and wherein a flushing medium is provided to the drill bit through a flushing channel The method comprises controlling a flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a first flow rate. The method further comprises obtaining, during the drilling process, a first set of drilling data representing one or more first physical phenomena associated with the drilling process, and also comprises determining from the obtained first set of drilling data, one or more first drilling process parameter values. Additionally, the method comprises determining a first drill bit condition based on a comparison of the one or more first drilling process parameter values with one or more respective predetermined first thresholds, and the method further comprises controlling, based on the determined first drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a second flow rate different from the first flow rate.

Description

METHOD AND ARRANGEMENT FOR CONDITIONING A DRILL BIT DURING A

ROTARY CORE DRILLING PROCESS INTO ROCK

Technical field

The disclosure relates to the field of core drilling, and more specifically to a method and arrangement for conditioning a drill bit during a rotary core drilling process into rock. The disclosure also relates to a computer-readable medium comprising instructions for performing the method, and to a drill rig comprising the arrangement.

Background

During exploration drilling, mineral exploration, and other applications, the method of core drilling may be used. Core drilling is performed by penetrating rock with a hollow drill bit for freeing a substantially cylindrical core composed of rock material. The core may then be the resulting drill hole and can be analysed to determine, e.g., the material, density, porosity etc. of the rock from which the core was taken.

The drilling equipment used for core drilling usually comprises a hollow drill string with a hollow drill bit attached to its front end. The drill bit is driven to penetrate the rock by feeding it into the rock with a feed force provided by a feeding arrangement, while simultaneously rotating the drill bit by using a rock drilling machine. The drill bit usually comprises a very hard cutting material, such as diamond, sintered together with a metal powder.

A challenge during core drilling is to achieve a high rate of penetration into the rock while simultaneously achieving a high lifetime for the drill bit. During a core drilling process, the condition of the drill bit may change, in particular when encountering very hard rock and/or when using wrong parameter settings for the drilling. If the drill bit gets, e.g., too blunt or damaged, it may need to be replaced, which can be very time-consuming due to core drilling holes often being very deep.

Summary

It is an objective of the disclosure to provide a method, an arrangement, a computer program product and drill rig that seeks to mitigate, alleviate or eliminate all or at least some of the above discussed drawbacks. More specifically, it is an object of the present disclosure to address conditioning a drill bit during a rotary core drilling process into rock, to prolong the life of the drill bit and increase the operational efficiency of the drilling process, e.g., via ensuring a high rate of penetration. A further objective of the disclosure is to provide solutions which are less dependent on manual input from an operator.

This and other objects are achieved by means of a computer-implemented method, arrangement, computer program product, and drill rig as defined in the appended independent claims.

According to a first aspect of the disclosure, it is provided a computer-implemented method for conditioning a drill bit during a rotary core drilling process into rock, which drilling process is performed by a drill rig and wherein a flushing medium is provided to the drill bit through a flushing channel. The method comprises controlling a flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a first flow rate. The method further comprises obtaining, during the drilling process, a first set of drilling data representing one or more first physical phenomena associated with the drilling process, and also comprises determining from the obtained first set of drilling data, one or more first drilling process parameter values. Additionally, the method comprises determining a first drill bit condition based on a comparison of the one or more first drilling process parameter values with one or more respective predetermined first thresholds, and the method further comprises controlling, based on the determined first drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a second flow rate different from the first flow rate.

The method may be used whenever a drill rig performs a rotary core drilling process into rock. When the flushing medium is provided to the drill bit through a flushing channel, the flushing medium may function, e.g., to wash away drill cuttings, such as grains of rock, in addition to cooling the drill bit. A change in flow rates, from the first flow rate to the second flow rate, will therefore affect the amount of drill cuttings washed away and the amount of cooling of the drill bit, and thereby result in a conditioning of the drill bit in response to the determined first drill bit condition. Thus, by said conditioning, the lifetime of the drill bit may be extended, and the drill bit will also be able to perform at an improved level for larger parts of the drilling process, achieving, e.g., a higher rate of penetration, thereby allowing for a more efficient drilling process.

Furthermore, since the method is computer-implemented, it also allows for a conditioning that is automated. This method is therefore particularly suited when any drilling process is to be conducted by a relatively inexperienced operator, since it reduces the risk of the drill bit being, e.g., damaged due to human error.

It should also be mentioned that a problem when drilling into rock is that the characteristics of the rock, such as its hardness, will be different at different depths. The provided method, in which a drill bit condition is determined and in which a conditioning of the drill bit is achieved during the drilling process itself, means that the drill bit can be kept in good shape even as the characteristics of the rock around the drill bit vary throughout the drilling process.

According to some embodiments, the second flow rate is lower than the first flow rate, the second flow rate preferably being between 50 and 95% of the first flow rate, more preferably between 70 and 90% of the first flow rate. Having the second flow rate lower than the first flow rate is useful for example if the determined first drill bit condition is indicative of the drill bit being blunt,

According to some embodiments, the method further comprises, when and/or after the flushing medium is controlled to be provided at the second flow rate, controlling a weight on bit to increase from a first weight level to a second weight level. An increase in the weight on bit is useful for example if the determined first drill bit condition is indicative of the drill bit being blunt. Such an increase will in that case increase the friction between the drill bit and the rock, and thereby functions to sharpen the drill bit.

According to some embodiments, the method further comprises controlling the flow rate of the flushing medium to stay between 90 and 110% of the second flow rate when controlling the weight on bit to increase. This is useful for example if the drill bit is blunt, and if the second flow rate is lower than the first flow rate, in which case the increased heat and lubrication due to the lower flow rate will have a synergistic sharpening effect with the increased friction due to the increasing in weight on bit. According to some embodiments, the method further comprises obtaining, during the drilling process, a second set of drilling data representing one or more second physical phenomena associated with the drilling process, and also comprises determining from the obtained second set of drilling data, one or more second drilling process parameter values. In these embodiments, the method additionally comprises determining a second drill bit condition based on a comparison of the one or more second drilling process parameter values with one or more respective predetermined second thresholds, and further comprises controlling, based on the determined second drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a third flow rate different from the second flow rate.

By determining the second drill bit condition, this may be used to effectively evaluate which effect the providing of the flow at the second flow rate has had on the drill bit, and in response to this control the flow of the flushing medium to be provided at a third flow rate.

According to some embodiments the third flow rate is between 80 and 110% of the first flow rate. This may be useful for example if the first drill bit condition was indicative of the drill bit being blunt, but the second drill bit condition is indicative of the drill bit having become sharp again. In that case, it might not be necessary to keep sharpening the drill bit, and a return to roughly the first flow rate would therefore now be suitable.

According to some embodiments, third flow rate is lower than the second flow rate, the third flow rate preferably being between 50 and 95% of the second flow rate, more preferably between 70 and 90% of the second flow rate. Such a reduction in flow to a third flow rate which is lower than the second flow rate, will cause further sharpening of the drill bit.

According to some embodiments, the method comprises, based on the determined second drill bit condition, triggering a warning event indicative of a failure in the conditioning of the drill bit. This is useful for example if the second drill bit condition is indicative of the drill bit being in substantially the same condition as the first drill bit condition. In this case, there might have been a failure in the conditioning, e.g., in that the conditioning might not have had as good of an effect as wanted, and a warning event may be triggered.

According to some embodiments, the one or more first drilling process parameter values are associated with one or more respective first drilling process parameters comprising one or more in the group of: a weight on bit, a torque applied to the drill bit, and a rate of penetration.

According to some embodiments, the one or more second drilling process parameter values are associated with one or more respective second drilling process parameters comprising one or more in the group of: a weight on bit, a torque applied to the drill bit, and a rate of penetration.

According to a second aspect of the disclosure, it is provided a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to perform the method according to the first aspect of the disclosure. The advantages for the computer-readable medium correspond to the advantages of the method according to the first aspect, as described above. The computer-readable medium may also comprise instructions for performing the method according to any of the previously mentioned embodiments, with corresponding advantages for said embodiments as described above.

According to a third aspect of the disclosure, it is provided an arrangement for conditioning a drill bit during a rotary core drilling process into rock, which drilling process is performed by a drill rig and wherein a flushing pump is configured to provide a flushing medium to the drill bit through a flushing channel. The arrangement comprises processing circuitry configured to control a flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a first flow rate. The processing circuitry is further configured to obtain, during the drilling process, a first set of drilling data representing one or more first physical phenomena associated with the drilling process, and also configured to determine from the obtained first set of drilling data, one or more first drilling process parameter values. In addition, the processing circuitry is configured to determine a first drill bit condition based on a comparison of the one or more first drilling process parameter values with one or more respective predetermined first thresholds, and the processing circuitry is further configured to control, based on the determined drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a second flow rate different from the first flow rate.

The advantages for the arrangement correspond to the advantages of the method according to the first aspect, as described above. The arrangement may also be configured for performing the method according to any of the previously mentioned embodiments, with corresponding advantages as described above.

According to some embodiments, the arrangement further comprises at least one sensor arranged to collect the first set of drilling data, wherein the at least one sensor comprises a transmitter arranged to transmit the first set of drilling data to the processing circuitry. The at least one sensor comprises one or more in the group of: a pressure gauge, a force gauge, a torque sensor, a position sensor, a speed sensor, a flow meter, a voltmeter, and an ampere meter.

According to some embodiments, the processing circuitry is further configured to control the flushing pump and/or a valve coupled to the flushing pump, for adjusting the flow of the flushing medium to the second flow rate.

According to a fourth aspect of the disclosure, it is provided a drill rig, which drill rig comprises a rock drilling machine for rotary core drilling, wherein the rock drilling machine is adapted for being attached to a drill string. The drill rig further comprises a flushing pump configured to provide a flow of a flushing medium through a flushing channel, as well as an arrangement according to the third aspect of the disclosure.

The same embodiments and advantages as applicable for the method, computer- readable medium, and arrangement, are also applicable to the drill rig according to the fourth aspect.

Brief description of the drawings

Fig. 1 illustrates a side view of an exemplary drill rig according to embodiments of the disclosure,

Fig. 2 shows schematically a computer-implemented method for conditioning a drill bit according to embodiments of the disclosure, Fig. 3 shows schematically a plurality of further method steps which may optionally be performed as part of the method of Fig. 2

Fig. 4A illustrates how a flow of a flushing medium and a weight on bit may vary over time when performing the method according to embodiments of the disclosure,

Fig. 4B illustrates how a rate of penetration may vary in connection to the method of Fig. 4A, and

Fig. 5 illustrates an exemplary arrangement for conditioning a drill bit according to embodiments of the disclosure.

Detailed description

Aspects of the present disclosure will be exemplified in the following in view of a particular kind of drill rig for core drilling. The disclosure is however applicable for all kinds of core drilling processes into rock, whether performed on the surface or underground.

The terminology used herein is for the purpose of describing particular aspects of the disclosure only and is not intended to limit the invention. It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of the present disclosure will be described and exemplified more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the embodiments set forth herein.

In some implementations and according to some aspects of the disclosure, the functions or steps noted in the blocks can occur out of the order noted in the operational illustrations. For example, two blocks shown in succession can in fact be executed substantially concurrently or the blocks can sometimes be executed in the reverse order, depending upon the functionality/acts involved. Also, the functions or steps noted in the blocks can according to some aspects of the disclosure be executed continuously in a loop.

It will be appreciated that when the present disclosure is described in terms of a method, it may also be embodied in one or more processors and one or more memories coupled to the one or more processors, wherein the one or more memories store one or more programs that perform the steps, services and functions disclosed herein when executed by the one or more processors.

In the following description of exemplary embodiments, the same reference numerals denote the same or similar components.

Fig. 1 illustrates a side view of an exemplary drill rig 101 according to aspects of the disclosure. The drill rig 101 is arranged to perform a rotary core drilling process into rock 102. The drill rig 101 comprises a rock drilling machine 103 for rotary core drilling which is adapted for holding a drill string 104. The drill string 104 is supported by a support 105 located by the rock 102, and the drill string 104 is further attached to a drill bit 106. Both the drill string 104 and the drill bit 106 are in the present example tube-shaped. The rock drilling machine 103 is arranged to rotate the drill string 104 and subsequently the drill bit 106. The rock drilling machine 103 may be driven, e.g., hydraulically or electrically.

The drill rig 101 further comprises a feeding arrangement 107. The feeding arrangement 107 is arranged for feeding the rock drilling machine 103 forward towards the rock 102 with a feed force. The feed force, together with any gravitational force of the drill string 104, determines a force applied to the drill bit 106, also called weight on bit (WOB), which pushes the drill bit 106 into the rock 102. The feeding arrangement 107 may be driven, e.g., hydraulically or electrically.

The type of drill bit 106 used in core drilling comprises a shaft which on its front end comprises a matrix. The shaft and matrix are both hollow, in the present example tube-shaped with a substantially cylindrical hollow interior. Embedded in the matrix is a cutting material such as diamond, tungsten carbide, very hard metals, and similar, which is adapted for cutting the rock.

As the drill bit 106 is driven to rotate by the rock drilling machine 103 and simultaneously pushed into the rock 102 by the feeding arrangement 107, the cutting material of the matrix causes the rock 102 to break and thereby the drill bit 106 penetrates the rock 102. Since the drill bit 106 is hollow, a substantially cylindrical core comprising rock material will be preserved within the hole as the drill bit 106 penetrates the rock 102. The core may then be freed from the rock and be taken out of the hole, for example by wireline, and then analysed further.

The drill rig 101 further comprises a flushing pump 108, which in the present example is connected to an upper end of the drill string 104 through a hose 109. The flushing pump 108 is arranged to provide a flow of a flushing medium through a flushing channel. In the present example, the flushing channel is comprised in the drill string 104, and the flushing pump 108 pumps the flushing medium via the hose 109, into the flushing channel of the drill string 104, and thereby a flow of the flushing medium is provided to the drill bit 106. The flow of the flushing medium may function to flush away drill cuttings, i.e. , grain, pieces and/or particles of rock which have been produced as the drill bit 106 breaks through the rock 102. The flushing medium may also function as a coolant, to prevent the drill bit 106 from overheating during the drilling process. The flushing medium may for example comprise water, oil, water-based mud, and/or oil-based mud.

Fig. 2 shows schematically a computer-implemented method for conditioning a drill bit 106 according to embodiments of the disclosure. The method is performable during a rotary core drilling process, which drilling process may be performed for example by the drill rig 101 of Fig. 1 , and wherein a flushing medium is provided to the drill bit 106 through a flushing channel.

The method comprises controlling S21 the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a first flow rate. This may comprise, e.g., controlling the flushing pump 108 and/or a valve coupled to the flushing pump 108. Providing the flow at the first flow rate may accomplish for example the flushing away of drill cuttings and/or the cooling of the bit.

The method further comprises obtaining S22, during the drilling process, a first set of drilling data representing one or more first physical phenomena associated with the drilling process. Such physical phenomena may be present, e.g., in the rock 102 itself, in the flushing medium, in a mechanical component such as the drill bit 106 or drill string 104, and/or in a hydraulic or electric component of the rock drilling machine 103 and/or feeding arrangement 107.

The first physical phenomena may comprise one or more pressures. Said pressures may comprise a pressure of the flushing medium within the flushing pump 108, the hose 109, the flushing channel and/or the hole. In the case when the rock drilling machine 103 is hydraulically driven, said pressures may comprise hydraulic pressure of a hydraulic fluid within the rock drilling machine 103, also referred to as rotation pressure. In the case when the feeding arrangement 107 is hydraulically driven, said pressures may comprise a hydraulic pressure in a hydraulic fluid of the feeding arrangement 107, also referred to as feed pressure. The first physical phenomena may comprise one or more forces, such as the weight on bit or a feed force of the feeding arrangement 107. The first physical phenomena may comprise one or more torques, for example a torque applied to the drill bit 106 or to the drill string 104. The first physical phenomena may comprise one or more positions and/or speeds, such as a position and/or speed of the drill bit 106, the drill string 104 and/or the rock drilling machine 103 during the drilling process. The first physical phenomena may also comprise a rotation speed or rotation angle of the drill bit 106 or the drill string 104. The first physical phenomena may comprise the flow rate of the flushing medium. The first physical phenomena may comprise one or more currents and/or voltages within circuitry of an electrically driven rock drilling machine 103 and/or electrically driven feeding arrangement 107. The first physical phenomena may also comprise a power within or consumed by such circuitry.

The first set of drilling data may comprise measurements of the physical phenomena. The drilling data may have been collected by at least one sensor, which may be arranged to, e.g., detect and/or measure the physical phenomena. The drilling data may be obtained from the at least one sensor and/or from some other device, such as a memory of a computer. Examples of suitable sensors will be discussed below.

The method further comprises determining S23 from the obtained first set of drilling data, one or more first drilling process parameter values. A first drilling process parameter value may be any type of value such as an absolute value (i.e. , a non- relative value), a relative value, a rate of change, a difference over time, a mean value or similar.

Some first drilling process parameter values may directly correspond to one or more of the first physical phenomena of which the first set of drilling data is representative. For example, data representative of the flow rate of the flushing medium may be used for determining a value of the flow rate itself, such as an absolute or mean value of the flow rate. Similarly, data representative of the rotation pressure within a hydraulically driven rock drilling machine 103 may be used to determine a value of the rotation pressure itself, such as an absolute value of or difference over time in rotation pressure.

Other first drilling process parameter values may more indirectly correspond to said first physical phenomena. For example, data representative of said rotation pressure within a hydraulically driven rock drilling machine 103 may instead and/or additionally be used to determine a value of the torque applied to the drill bit 106, since it is the rotation pressure with which the rotation is driven. Similarly, data representative of the feed pressure within a hydraulically driven feeding arrangement 107 may be used to determine a value for the feed force and/or the weight on bit. Data representative of the position and/or speed of the drill bit 106, drill string 104 and/or rock drilling machine 103 may be used to determine a value of the rate of penetration. Data representative of a voltage and/or current within a circuit of an electrically driven rock drilling machine 103 may be used to determine a value of the torque applied to the drill bit 106. Similarly, data representative of a voltage and/or current within a circuit of an electrically driven feeding arrangement 107 may be used to determine a value of the feed force and/or the weight on bit.

In a preferred embodiment, the one or more first drilling process parameter values are associated with one or more respective first drilling process parameters comprising one or more in the group of: a weight on bit, a torque applied to the drill bit 106, and a rate of penetration.

Each first drilling process parameter value needs only to be associated with its respective first drilling process parameter, and need not necessarily be, e.g., a determined quantity of the parameter itself. For example, a value of the feed force is associated with the weight on bit, since the weight on bit is a substantially linear function of the feed force. A value of the feed pressure in a hydraulically driven feeding arrangement 106 is also associated with the weight on bit, since the weight on bit is a substantially linear function also of the feed pressure. A value of a rotation pressure in a hydraulically driven rock drilling machine 106 is associated with the torque applied to the drill bit 106, since the torque is a substantially linear function of the rotation pressure. In particular, a drilling process parameter value may be considered associated with a respective drilling process parameter for example if the relationship between the drilling process parameter and the drilling process parameter value is substantially in a linear relationship, or in an otherwise causal or correlational relationship.

It should be appreciated that more than one first drilling process parameter value may also be associated with a single first drilling process parameter, e.g., the one or more first drilling process parameter values may comprise multiple values associated with the weight on bit.

The method further comprises determining S24 a first drill bit condition based on a comparison of the one or more first drilling process parameter values with one or more respective predetermined first thresholds. The first drill bit condition may for example be indicative of a current, previous and/or changing status of the drill bit 106. The first drill bit condition may be indicative, e.g., of the drill bit 106 being sharp or blunt or of a change in any of these properties. Each predetermined first threshold may be an upper threshold or a lower threshold.

The predetermined first thresholds may be set prior to commencing the drilling process, for example set by an operator or provided by a system and/or database. The first thresholds may alternatively be determined previously during the drilling process by, e.g., an operator and/or by an automated control system, so that they are predetermined at least when the comparison is performed. The thresholds may be selected based on relevant conditions of the drilling process, such as type of drill bit, type of flushing medium, type of rock etc., but also on previously achieved parameter values, e.g., a previously achieved rate of penetration during the drilling process.

As an example, the drill bit 106 being blunt may result in that the weight on bit necessary to uphold a desired rate of penetration becomes too high. Therefore, a first drill bit condition indicative of the drill bit 106 being blunt may be determined based on a comparison between the weight on bit and an upper threshold for the weight on bit. Said upper threshold may be, e.g., around 80% of a maximally allowed weight on bit for the specific type of drill bit 106, which maximally allowed weight on bit should never be surpassed during drilling. The drill bit 106 being blunt may result in a drop in torque, as the drill bit 106 loses friction with the rock 102, so a first drill bit condition indicative of the drill bit 106 being blunt may be determined based on a comparison of the torque with a lower threshold for the torque. Since the absolute value for the torque generally is quite a lot higher at deeper hole depths, it may alternatively be more useful to compare a difference over time in torque with a lower threshold for difference over time. Such a lower threshold may for example correspond to a total drop in torque of 5% over 30 s, i.e, of a difference over time of minus 5% over said 30 s. The drill bit 106 being blunt may result in a drop in rate of penetration as the drill bit 106 struggles to break through the rock 102 fast enough, so that a drill bit condition indicative of the drill bit 106 being blunt may be determined based on a comparison of the rate of penetration with a lower threshold for the rate of penetration. Said lower threshold for the rate of penetration may be, e.g., around 50% of a desired rate of penetration to uphold during the drilling.

The first drill bit condition may also be based on a comparison of more than one first drilling process parameter values with more than one respective predetermined first thresholds. For example, a first drill bit condition indicative of the drill bit 106 being blunt may be determined based on a comparison of both the rate of penetration and rotation pressure with their respective lower thresholds. In some embodiments, it would suffice for at least one of rate of penetration and rotation pressure reaching their respective lower thresholds; in other embodiments, both would need to do so. In the present example, a drill bit condition indicative of the drill bit 106 being blunt is determined, but similar types of drilling process parameter values and respective thresholds may be used to determine other drill bit conditions, e.g., indicative of the drill bit 106 being sharp.

The method further comprises controlling S25, based on the determined first drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a second flow rate different from the first flow rate. When the flushing medium is controlled to be provided at the second flow rate, this will condition the drill bit 106 in response to the determined first drill bit condition.

The second flow rate may be lower than the first flow rate. For example, if the determined drill bit condition indicates that the drill bit 106 is too blunt, the flow may be controlled to be provided at a lower flow rate. In this case a reduction in flow rate will reduce the cooling of the drill 106 bit in addition to lubricating the drill bit 106 by lessening the amount of drill cuttings flushed away. The resulting heat and lubrication during the drilling will subsequently cause a sharpening of the drill bit 106, as the matrix is worn down and new cutting material is exposed. Such a sharpening will restore and/or increase the cutting ability of the drill bit 106 which will, e.g., allow the drill bit 106 to break through the rock 102 faster, achieving a higher rate of penetration. In this case, the second flow rate is preferably between 50 and 95% of the first flow rate, more preferably between 70 and 90% of the first flow rate, to cause suitable sharpening of the drill bit 106.

The second flow rate may alternatively be higher than the first flow rate. For example, if the determined drill bit condition indicates that the drill bit 106 is sharp enough, the flow may be controlled to be provided at a higher flow rate, to prevent the matrix from unnecessarily being worn down.

In an optional step, the method may comprise, when and/or after the flushing medium is controlled to be provided at the second flow rate, controlling S26 a weight on bit to increase from a first weight level to a second weight level. The increase may for example occur continuously, ramp-wise, and/or step-wise in one or more steps. The controlling may comprise providing a control signal to the feeding arrangement 107 for increasing the feed force, which would cause an increase in the weight on bit. This optional step is particularly useful if the first drill bit condition is indicative of the drill bit 106 being blunt. By increasing the weight on bit, the drill bit 106 is pushed harder into the rock 102, which increases the friction between the drill bit 106 and the rock 102, thereby causing further sharpening of the drill bit 106.

In some embodiments, the increase starts after a predetermined time period has passed in relation to when the flushing medium was controlled to be provided at the second flow rate. For example, it may be suitable to first increase/lower the flow rate to the second flow rate, and then wait a predetermined time before increasing the weight on bit. Said predetermined time may be set, e.g., to a value between 5-30 s.

In some embodiments, the method further comprises controlling the flow rate of the flushing medium to stay between 90 and 110% of the second flow rate when controlling the force to increase.

This is particularly useful if the drill bit 106 is blunt, and when the second flow rate is lower than the first flow rate. By letting the flow rate stay between 90% and 110% of the second flow rate when controlling the weight on bit to increase, the increased heat and lubrication due to the lower second flow rate will have a synergistic effect with the increased friction due to the increasing in weight on bit, causing an even better sharpening of the drill bit 106.

Fig. 3 shows schematically a plurality of further method steps which may optionally be performed as part of the method of Fig. 2. The further method steps of Fig. 3 may be performed after the steps S21-S26 of Fig. 2 or partially overlapping with said steps. As indicated in Fig. 3, the method may therefore further comprise obtaining S31 , during the drilling process, a second set of drilling data representing one or more second physical phenomena associated with the drilling process. The discussion and previously mentioned examples regarding the first set of drilling data and the first physical phenomena applies equally well to the second set of drilling data and second physical phenomena. In particular, the second set of drilling data may for example obtained from at least one sensor, which at least one sensor is arranged for collecting the second set of drilling data. In those embodiments in which sensors are used for collecting both the first and second sets of drilling data, it should be noted the same, partially different or entirely different sensors may be used for collecting the first and second sets of drilling data respectively. It should be noted that the one or more second physical phenomena may be the same as, partially overlapping with, or not overlapping with the one or more first physical phenomena.

The method may further comprise determining S32 from the obtained second set of drilling data, one or more second drilling process parameter values. The discussion and previously mentioned examples regarding the first drilling process parameter values applies equally well to the second drilling process parameter values. In particular, the one or more second drilling process parameter values may be associated with one or more respective second drilling process parameters comprising one or more in the group of: the weight on bit, the torque applied to the drill bit 106, and the rate of penetration. Such one or more second drilling process parameters may be the same as, partially overlapping, or not overlapping with any one or more first drilling process parameters as mentioned above. For example, if the one or more first drilling process parameters consists only of the weight on bit, the one or more second drilling process parameters may also consist only of the weight on bit (same), or comprise both the weight on bit and the torque (partially overlapping), or consist only of the torque and rate of penetration (not overlapping). It should be appreciated then that any selection of second drilling process parameters may therefore be independent of any selection of first drilling process parameters.

The method may further comprise determining S33 a second drill bit condition based on a comparison of the one or more second drilling process parameter values with one or more respective predetermined second thresholds. The discussion and previously mentioned examples regarding the first drill bit condition applies equally well to the second drill bit condition. The discussion and previously mentioned examples regarding the predetermined first thresholds also applies equally well to the predetermined second thresholds. It should be noted that, in the case that the set of first drilling parameters (partially) overlaps with the set of second drilling parameters, the respective predetermined first thresholds for these overlapping drilling parameters may be the same as, or different from, the respective predetermined second thresholds for these overlapping drilling parameters. For example, if the weight on bit is both a first drilling parameter and a second drilling parameter, the first threshold for the weight on bit may be the same as, or higher, or lower, than the second threshold for the weight on bit.

The method may further comprise controlling S34, based on the determined second drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a third flow rate different from the second flow rate. The second drill bit condition may effectively represent which effect the providing of the flushing medium at the second flow rate has had on the drill bit 106, and the flushing medium may in response be controlled to be provided at the third flow rate. In some embodiments, the third flow rate is between 80 and 110% of the first flow rate. This may be useful for example if the first drill bit condition was indicative of the drill bit 106 being blunt, but the second drill bit condition is indicative of the drill bit 106 having become sharp again. In that case, it might not be necessary to keep sharpening the drill bit 106, and a return to roughly the first flow rate would therefore now be suitable. It is however not always needed to have the third flow rate be equal to the first flow rate. For example, if the first drill bit condition was indicative of the drill bit 106, e.g., being blunt, it may be possible to infer that the first flow rate was not ideal for, e.g., the present rock characteristics: otherwise the drill bit 106 would not have become blunt in the first place. Therefore, by letting the third flow rate be, e.g., between 80 to 95% or between 105 and 110% of the first flow rate, said third flow rate may then be better suitable for the current rock characteristics than the first flow rate, and by providing the flushing medium at said third flow rate it is possible to reduce the need for performing any further conditioning in the future. Therefore, it is advantageous to have the opportunity of the third flow rate lying in the broader interval of 80 to 110% of the first flow rate, rather than only being, e.g., equal to the first flow rate.

In some embodiments, the third flow rate is lower than the second flow rate, the third flow rate preferably being between 50 and 95% of the second flow rate, more preferably between 70 and 90% of the second flow rate. This may be useful for example if the first drill bit condition was indicative of the drill bit 106 being blunt, and the second drill bit condition indicative of the drill bit 106 still being relatively blunt despite a sharpening caused by the second flow rate being lower than the first flow rate. In that case, a reduction in flow to a third flow rate which is lower than the second flow rate, will cause further sharpening of the drill bit 106. It should be appreciated that this process may also be iteratively repeated by later lowering the flow to a fourth flow rate, then to a fifth flow rate, etc., until a sufficient amount of sharpening has been occurred. Such an iteration may also involve the weight on bit, which may similarly be iteratively increased. For example, if the weight on bit was increased from a first weight level to a second weight level after a lowering of the flow rate the second flow rate, the weight on bit may then further be increased to a third weight level after lowering the flow rate to the third flow rate, and so on. In some embodiments, the method further comprises, based on the determined second drill bit condition, triggering S35 a warning event indicative of a failure in the conditioning of the drill bit 106. This may be suitable for example if none of the one or more second drilling process parameter values have reached their respective predetermined second thresholds after a predetermined maximum time has passed. Said predetermined maximum time may e.g. be set to a value between 40-120 s. The triggering of the warning event may comprise providing an operator and/or an automated control system with a warning signal and/or a warning command. The triggering may comprise controlling the conditioning and/or the drilling process to end. The third flow rate may be relatively large, e.g., larger than the second flow rate, to flush away more drill cuttings and cool the drill bit 106, thereby preventing any damage to the drill bit 106 which could arise as a consequence of the failure in conditioning. The third flow rate may alternatively be relatively low, e.g., substantially equal to zero, whereby the flow of the flushing medium is substantially turned off, which may be suitable for example if the drilling process is to end. Based on the warning event, it may be decided to, e.g., initiate another conditioning, to troubleshoot the failure, and/or to replace the drill bit 106 with a new one.

Fig. 4A illustrates how a flow of a flushing medium and a weight on bit may vary over time when performing the method according to embodiments of the disclosure, and Fig. 4B illustrates how a rate of penetration may vary in connection to the method of Fig. 4A. In Fig. 4Athe flow rate is plotted against time in solid lines, with the weight on bit being plotted against time in dashed lines. In Fig. 4B, the rate of penetration is plotted against the same time axis as in Fig. 4A. To best illustrate the method, Figs. 4A and 4B show an abstract and simplified visualization of the conditioning, but in practice the shapes of the shown curves may of course be somewhat different. Note in particular that each vertical axis has an axis break, so that the shown graphs are not to be considered to represent absolute values, only relative values.

The method is here exemplified in a situation where the drill bit 106 has become blunt during the drilling process, and the conditioning of the drill bit 106 causes a sharpening of the drill bit 106. The method may however be performed also in connection with other drill bit conditions, as explained previously. At the start, the flow of the flushing medium is controlled to be provided at a first flow rate Q1 . During the time when the flow rate is provided at the first flow rate Q1 , the weight on bit is controlled to be gradually increasing, which may be done in order to preserve a relatively constant rate of penetration despite the drill bit 106 slowly becoming blunter. However, despite this gradual increase, it can be seen in Fig. 4B that the rate of penetration is initially dropping over time. A first set of drilling data is obtained, which in the present example is representative of a hydraulic pressure within the feeding arrangement 107. Based on the first set of drilling data, a first drilling process parameter value is determined, which in the present example is a value of the weight on bit. A predetermined first threshold F1 is set for the weight on bit, which if reached indicates that the drill bit 106 has become blunt. The determined value of the weight on bit is compared to the predetermined first threshold F1 , and at a first timepoint T 1 , when the weight on bit has reached this threshold, it is determined based on this comparison a first drill bit condition indicating that the drill bit 106 has become blunt. Thereafter, based on this first drill bit condition, the flow of the flushing medium is controlled to be provided at a second flow rate Q2, which in the present example is lower than the first flow rate Q1 . As explained earlier, the providing of the flow at a lower flow rate will cause a sharpening of the blunt drill bit 106. It can be seen in Fig. 4B, that the rate of penetration starts increasing after the first timepoint T1 as a result of this sharpening.

The providing of the flow at the lower flow rate may itself suffice for sharpening the drill bit 106. In the present example however, a further sharpening is wanted. Therefore, starting at a second timepoint T2, the weight on bit is controlled to increase from a first weight level, which in the present example is the same as the predetermined first threshold F1 , to a second weight level F2. As explained earlier, this increase will cause a further sharpening of the drill bit 106. As can be seen in Fig. 4A, when increasing the force, the flow rate is in this example controlled to stay constant, and therefore in particular to stay between 90 and 110% of the second flow rate Q2. When the flow rate stays between 90 and 110% of the second flow rate when increasing the force, the reduction in flushing and cooling together with the increased friction has a synergistic sharpening effect, as discussed earlier. As shown in Fig. 4B, the rate of penetration increases further after the second timepoint T2, due to this additional sharpening. In the present example, a second set of drilling data representative of a plurality of positions of the drill bit 106 is obtained. From the second set of drilling data, a value of the rate of penetration is determined. The value of the rate of penetration is compared with a respective predetermined second threshold V1 for the rate of penetration, and at a third timepoint T3, it is determined based on this comparison a second drill bit condition indicative of the drill bit 106 having become sharp again. Subsequently, the flow of the flushing medium is controlled to be provided at a third flow rate Q3, which in the present example is higher than the second flow rate, since there now is less need in sharpening the drill bit 106 further. It can also be seen the weight on bit is lowered after this timepoint, since the bit is now sharp enough to uphold a desired rate of penetration with this lower weight on bit. In the present example, the third flow rate is lower than the first flow rate, but not less than 80% of the first flow rate. As explained earlier, by not returning to exactly the first flow rate, this may function to reduce the need of performing any additional sharpening in the future, since this third flow rate may be better suited to, e.g., the present rock characteristics. In the present example, this is indicated in Fig. 4B by the rate of penetration stabilizing at a relatively high level after the third timepoint T3.

As an example, when drilling with a core drill bit of size type N, it may be suitable in the above to have the first flow rate Q1 at 35 L/min, the second flow rate Q2 at 28 L/min, the third flow rate Q3 at 33 L/min, the first weight level F1 at 32 kN, the second weight level F2 at 38 kN, and the rate of penetration threshold V1 at 24 cm/min.

Fig. 5 illustrates an exemplary arrangement 50 for conditioning a drill bit 106 according to embodiments of the disclosure. The drill rig 101 may, in addition to comprising the rock drilling machine 103 and the flushing pump 108, comprise said arrangement 50. The arrangement 50 may alternatively be located elsewhere and interact with the drill rig 101 for example by wireless signal. The arrangement 50 may also be incorporated in a separate module, which may be readily installed in any type of suitable drill rig. The arrangement 50 comprises processing circuitry 51 configured to perform the method steps S21-S25 of Fig. 2. It should however be appreciated that the processing circuitry may further be configured to perform any of the above-mentioned embodiments of the methods described in relation to Figs. 2-4. The processing circuitry may comprise one or more processors 51a, which one or more processors 51a may comprise for example one or more general-purpose central processing units (CPUs), one or more digital signal processors (DSPs), one or more application-specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more programmable logic devices, and/or any other one or more discrete or logic devices/circuits/chipsets.

The processing circuitry may further comprise one or more memories 51 b, which one or more memories 51b may comprise for example one or more read-only memories (ROM), one or more a random-access memories (RAM), and/or one or more nonvolatile RAM (NVRAM). Stored upon the one or more memories 51 b might be one or more computer programs or any other type of computer code comprising instructions which, when executed by the processing circuitry, causes the arrangement to perform the method for conditioning a drill bit according to embodiments of the disclosure.

Fig. 5 also depicts a computer-readable medium 53 comprising instructions which, when executed by a computer, cause the computer to carry out the method for conditioning a drill bit according to embodiments of the disclosure. The computer- readable medium may for example be a hard drive, an USB stick, or a CD-ROM.

In some embodiments, the arrangement 50 further comprises at least one sensor 52 arranged to collect the first set of drilling data, wherein the at least one sensor 52 comprises a transmitter 52a arranged to transmit the first set of drilling data to the processing circuitry. The transmitter may be arranged to transmit the first set of drilling data to the processing circuitry in any suitable way, such as by wired or wireless signal.

The at least one sensor 52 may comprise a pressure gauge arranged to collect data representative of a pressure of the flushing medium, a rotation pressure and/or a feed pressure. The at least one sensor 52 may comprise a force gauge arranged to collect data representing a force, such as the weight on bit or a feed force of the feeding arrangement 107. The at least one sensor 52 may comprise a torque sensor arranged to collect data representing a torque, for example a torque applied to the drill bit 106 or to the drill string 104. The at least one sensor 52 may comprise a position sensor and/or a speed sensor arranged to collect data representing a position and/or speed of, e.g., the drill bit 106, the drill string 104 and/or the rock drilling machine 103 during the drilling process. The at least one sensor 52 may comprise a flow meter arranged to collect data representing the flow rate of the flushing medium through the flushing channel. The at least one sensor 52 may comprise a voltmeter and/or an ampere meter arranged to collect data representing a voltage and/or current respectively, for example within a circuit of a component of the drill rig 101.

It is also possible to have more than one sensor 52 of the same or similar type. For example, two pressure gauges may be used, one of which may collect data representing a rotation pressure, and the other which may collect data representing a feed pressure.

In some embodiments, these mentioned sensors and/or types of sensors may also be used for collecting the above-mentioned second set of drilling data, where applicable, and that such sensors for collecting the second set of drilling data may be comprised in the arrangement 50 as well.

In some embodiments, the processing circuitry 50 is further configured to control the flushing pump 108 and/or a valve coupled to the flushing pump 108, for adjusting the flow of the flushing medium to the second flow rate Q2. Controlling the flushing pump 108 and/or said valve enables for accurate adjustment of the flow. Such a valve may be coupled to the flushing pump 108 in a number of ways. For example, it may be directly attached to the flushing pump 108. Alternatively, it may be placed for example on the hose 109 and thereby coupled to the flushing pump 108 via the hose 109.

Claims

1 . A computer-implemented method for conditioning a drill bit (106) during a rotary core drilling process into rock (102), which drilling process is performed by a drill rig (101 ) and wherein a flushing medium is provided to the drill bit (106) through a flushing channel, the method comprising:

- controlling (S21 ) a flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a first flow rate (Q1 );

- obtaining (S22), during the drilling process, a first set of drilling data representing one or more first physical phenomena associated with the drilling process;

- determining (S23) from the obtained first set of drilling data, one or more first drilling process parameter values;

- determining (S24) a first drill bit condition based on a comparison of the one or more first drilling process parameter values with one or more respective predetermined first thresholds; and

- controlling (S25), based on the determined first drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a second flow rate (Q2) different from the first flow rate (Q1 ).

2. The method according to claim 1 , wherein the second flow rate (Q2) is lower than the first flow rate (Q1 ), the second flow rate (Q2) preferably being between 50 and 95% of the first flow rate (Q1 ), more preferably between 70 and 90% of the first flow rate (Q1 ).

3. The method according to any one of claims 1-2, further comprising, when and/or after the flushing medium is controlled to be provided at the second flow rate (Q2):

- controlling (S26) a weight on bit to increase from a first weight level (F1 ) to a second weight level (F2).

4. The method according to claim 3, further comprising: controlling the flow rate of the flushing medium to stay between 90 and 110% of the second flow rate (Q2) when controlling the weight on bit to increase.

5. The method according to any one of claims 1-4, further comprising:

- obtaining (S31), during the drilling process, a second set of drilling data representing one or more second physical phenomena associated with the drilling process;

- determining (S32) from the obtained second set of drilling data, one or more second drilling process parameter values;

- determining (S33) a second drill bit condition based on a comparison of the one or more second drilling process parameter values with one or more respective predetermined second thresholds; and

- controlling (S34), based on the determined second drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a third flow rate (Q3) different from the second flow rate (Q2).

6. The method according to claim 5, wherein the third flow rate (Q3) is between 80 and 110% of the first flow rate (Q1 ).

7. The method according to claim 5, wherein the third flow rate (Q3) is lower than the second flow rate (Q2), the third flow rate (Q3) preferably being between 50 and 95% of the second flow rate (Q2), more preferably between 70 and 90% of the second flow rate (Q2).

8. The method according to any one of claims 5-7, further comprising, based on the determined second drill bit condition:

- triggering (S35) a warning event indicative of a failure in the conditioning of the drill bit (106).

9. The method according to any one of claims 1-8, wherein the one or more first drilling process parameter values are associated with one or more respective first drilling process parameters comprising one or more in the group of: a weight on bit, a torque applied to the drill bit (106), and a rate of penetration.

10. The method according to any one of claims 5-9, wherein the one or more second drilling process parameter values are associated with one or more respective second drilling process parameters comprising one or more in the group of:

- a weight on bit,

- a torque applied to the drill bit (106), and

- a rate of penetration.

11. A computer-readable medium (53) comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of claims 1 -10.

12. An arrangement (50) for conditioning a drill bit (106) during a rotary core drilling process into rock (102), which drilling process is performed by a drill rig (101 ) and wherein a flushing pump (108) is configured to provide a flushing medium to the drill bit (106) through a flushing channel, the arrangement (50) comprising processing circuitry (51 ) configured to:

- control a flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a first flow rate (Q1 );

- obtain, during the drilling process, a first set of drilling data representing one or more first physical phenomena associated with the drilling process;

- determine from the obtained first set of drilling data, one or more first drilling process parameter values;

- determine a first drill bit condition based on a comparison of the one or more first drilling process parameter values with one or more respective predetermined first thresholds; and

- control, based on the determined drill bit condition, the flow of the flushing medium through the flushing channel, wherein the flushing medium is controlled to be provided at a second flow rate (Q2) different from the first flow rate (Q1 ).

13. The arrangement (50) according to claim 12, further comprising at least one sensor (52) arranged to collect the first set of drilling data, wherein the at least one sensor (52) comprises a transmitter (52a) arranged to transmit the first set of drilling data to the processing circuitry (51 ), wherein the at least one sensor (52) comprises one or more in the group of:

- a pressure gauge,

- a force gauge,

- a torque sensor,

- a position sensor,

- a speed sensor,

- a flow meter,

- a voltmeter, and

- an ampere meter.

14. The arrangement according to any one of claims 12-13, wherein the processing circuitry (50) is further configured to control the flushing pump (108) and/or a valve coupled to the flushing pump, for adjusting the flow of the flushing medium to the second flow rate (Q2).

15. A drill rig (101) comprising:

- a rock drilling machine (103) for rotary core drilling, wherein the rock drilling machine is adapted for holding a drill string (104);

- a flushing pump (108) configured to provide a flow of a flushing medium through a flushing channel; and

- an arrangement (50) according to any one of claims 12-14.