Method and system for detecting the condition of a joint of a drill string

Abstract

The invention relates to a method for determining a state of at least one joint of a drill string (107) of a drilling rig, the drilling rig comprising a percussion device comprising a percussion element for introducing a stress wave into the drill string (107), and a sensor for sensing a stress wave in the drill string (107) caused by a percussion of the percussion element, the method comprising, when the percussion element introduces a stress wave into the drill string (107): determining a representation of an incident stress wave caused by the percussion element; determining a representation of a reflected wave representing a reflection of the incident stress upon reaching the at least one joint; estimating a stiffness of the at least one joint by estimating a force exerted on the at least one joint by the incident wave and a displacement caused by the force; and generating a signal representing the state of the at least one joint based on the estimated stiffness.

Description

Technical Field

[0001] This invention relates to mining, and more particularly to methods and systems for detecting the condition of drill string joints. The invention also relates to computer programs for implementing the methods according to the invention. Background Technology

[0002] Rock drilling rigs have applications in many fields. For example, they can be used for tunnel excavation, open-pit mining, underground mining, rock reinforcement, and well drilling. They can also be used for drilling blasting holes, grouting holes, holes for installing rock anchors, water wells and other wells, piling, and foundation drilling. Therefore, rock drilling rigs have a wide range of uses.

[0003] The actual fracturing of rock is typically carried out by a drill bit that contacts the rock, usually connected to a drilling machine via a drill string. Drilling can be done in various ways, including, for example, percussion drilling, where, for instance, the percussion element of the drilling machine, such as an impact piston, repeatedly strikes the drill bit, typically connected to the drill string by impact, to transmit shock pulses, or stress waves, in the form of shock waves to the drill bit and further into the rock. Percussion drilling can be combined with rotation to allow the drill bit's knobs, inserts, to strike new rock with each stroke, thereby increasing drilling efficiency.

[0004] The drill bit can be pressed against the rock during drilling by means of feed force to ensure that as much impact energy as possible from the impact device is transferred to the rock.

[0005] To achieve an effective percussion drilling process, it is crucial to set various drilling parameters in a manner that allows as much of the shock wave energy generated by the impact element as possible to be transmitted into the rock to break it. If the drill bit is not firmly pressed against the rock, energy may be reflected to an undesirable degree and back into the drilling rig, potentially causing excessive wear or damage. This can also occur if the drill string joints (usually threaded joints) are not properly tightened. Harmful reflections can also occur if the shock wave energy is too low relative to the force used to press the drill string against the rock.

[0006] When drilling longer holes, for example, in rock, multiple drill rods can be joined together, for example, by screwing them together, to extend the drill string, thereby allowing the hole to be drilled to the desired length. Summary of the Invention

[0007] The object of this invention is to provide a method and system for identifying loose joints, particularly loose threaded joints, during impact drilling.

[0008] According to the present invention, a method is provided for determining the state of at least one joint of a drill string of a drilling rig, the drilling rig comprising: an impact device including an impact element for introducing a shock wave into the drill string; and a sensor for sensing a stress wave in the drill string caused by the impact of the impact element, the method comprising, when the impact element introduces the stress wave into the drill string, performing the following operations: determining a representation of an incident stress wave caused by the impact element; and determining a representation of a reflected wave, the reflected wave representing the reflection of the incident stress upon reaching the at least one joint.

[0009] The stiffness of at least one joint is estimated by estimating the force exerted on at least one joint by the incident wave and the displacement caused by the force, and a signal representing the state of the at least one joint is generated based on the estimated stiffness.

[0010] As mentioned above, properly tightened joints are a requirement for efficient drilling. Normally, threaded joints are also secured by the shock waves passing through them during drilling. However, under adverse conditions, joints can become loose, which degrades the drilling process and causes excessive wear on the threaded joints.

[0011] There are also situations where loosening of the joints is desired. After drilling, the drill string retracts, and the drill rods loosen from each other. However, during drilling, the joints may become so tightly tightened due to the shock waves passing through them during drilling that they cannot be loosened by the rotary motor of the drilling machine alone.

[0012] To address this issue, for example, an operator could end drilling by briefly impacting the drill string with the impact device without pressing the drill string against the rock being drilled, thus loosening the joint. The success of this may depend on the operator's skill. This process may damage parts of the drilling rig and may take longer than necessary.

[0013] According to the present invention, such a problem can be mitigated by a system and method in which the state of the joints (whether they are loose or tight) can be accurately estimated and utilized during drilling and when the joints are loosened before the drill string is retracted.

[0014] The determination of the joint's condition is performed by estimating the force exerted on at least one joint by the incident wave generated by the impact of the impact element and further determining the displacement caused by said force when the impact is on the joint whose condition is being determined. The estimated stiffness can then be used to generate a signal indicating the condition of at least one joint (i.e., whether the joint is tightened or loose). This signal can be used by the drilling rig control system in automated drilling or by an operator manually controlling the drilling control parameters.

[0015] The displacement of the joint can be determined by estimating the velocity v of the stress wave as it propagates through the drilled steel. thread (It can be estimated as:) ), and for example according to d=∫v thread dt is integrated over the velocity of the stress wave.

[0016] According to an embodiment of the present invention, the force acting on the joint due to the incident stress wave can be estimated by multiplying the sum of the incident wave and the reflected wave by the cross-sectional area of ​​a component of the drill string, such as the cross-sectional area of ​​the drill rod.

[0017] According to an embodiment of the invention, at least one of the representations of the incident stress wave and the reflected stress wave is filtered before estimating the joint stiffness. In this way, noise in the signal, such as that caused by other reflections in the drill string, can be attenuated and / or removed to allow for a more accurate estimation of the joint stiffness.

[0018] According to an embodiment of the invention, offsets in the representation of incident and / or reflected waves are removed before estimating the joint stiffness. These offsets may be related to signal levels caused by other reflections in the drill string, and removing these offsets also allows for a more accurate estimation of the joint stiffness.

[0019] According to an embodiment of the invention, stiffness is estimated as the change in force exerted on the at least one joint by the incident wave relative to the displacement of the joint caused by the force. This provides a reliable measure of the joint's stiffness. According to an embodiment of the invention, when the change in force relative to the change in displacement exceeds a threshold, it is determined that the joint is properly tightened. Conversely, when the change in force relative to the change in displacement is below the threshold, it can be determined that the joint is loose.

[0020] According to an embodiment of the invention, multiple thresholds are used to make it possible, for example, to determine whether a joint is about to become loose before it has actually become loose.

[0021] According to an embodiment of the invention, the drilling rig control system continuously monitors the estimated stiffness of one or more joints of the drill string, wherein the drilling rig control system can adjust one or more drilling control parameters based on the estimated stiffness of at least one monitored joint. Such control parameters may include impact pressure, feed pressure, feed force, feed rate, rotational pressure, rotational flow rate, and rotational speed.

[0022] Stiffness can be estimated for multiple or all joints in a drill string. The generated signals can indicate whether a specific joint is loose, or alternatively, whether any or all joints are loose.

[0023] According to an embodiment of the invention, when all joints are to be loosened, for example when the drill string is to be retracted from the drilled hole, it can be determined whether a joint is loose for each joint, and when all joints are loose, a signal indicating that all joints are loose can be generated. In this way, for example, once a joint is loosened, the impact applied by the operator or the drilling rig control system can be stopped, thereby avoiding excessive impact. For example, once it is determined that all joints are loose, the drilling rig control system can stop applying impact to the drill string.

[0024] The state of a particular connector can be determined by estimating when the sensor can detect reflections originating from that connector in time.

[0025] According to an embodiment of the present invention, when the first connector is a certain distance away from the sensor, causing the incident wave and the reflected wave to mix, compensation can be made for the representation of the incident wave based on the reflection, so that the representation of the incident wave is also effective when used to estimate the stiffness of the connector further away from the sensor.

[0026] According to embodiments of the invention, a first sensor element, such as a portion of a sensor or a separate sensor, is used to determine the representation of the incident wave, and a second sensor element is used to determine the representation of the reflected wave. A combination of sensors can also be used to determine both the incident and reflected waves. In this way, for example, compensation for the incident wave for the reflected wave is not required, even if the incident and reflected waves are temporally congruent at the locations of the sensor elements.

[0027] Regarding sensors further, sensors that can contact the drill string or are arranged close to the drill string can be used for non-contact measurement of stress waves in the drill string. Such non-contact sensors can operate, for example, based on the principle of measuring changes in the magnetization of the drill string in response to stress waves traveling within it. Various suitable sensors or combinations thereof are known to those skilled in the art of rock drilling, and therefore will not be discussed in detail herein.

[0028] Further features and advantages of the invention are indicated in the detailed description of the exemplary embodiments set forth below and in the accompanying drawings. Attached Figure Description

[0029] Figure 1 An exemplary drilling rig to which embodiments of the present invention can be applied is shown;

[0030] Figure 2A It shows Figure 1 The drill string of the drilling rig shown;

[0031] Figure 2B It shows Figure 2A The cross-sectional area of ​​the drill string joint;

[0032] Figure 3 It shows the relationship with Figure 2A Exemplary stress wave measurements related to drill strings;

[0033] Figures 4A to 4B The stress wave cuts of multiple impact pistons with two different joints are shown.

[0034] Figure 5 An exemplary method according to an embodiment of the present invention is shown;

[0035] Figures 6A to 6B It shows Figures 4A to 4B The estimated stiffness of the impact;

[0036] Figure 7 Estimates of the stiffness of multiple joints for multiple impacts are shown;

[0037] Figure 8 Estimates of the stiffness of multiple joints for multiple impacts are also shown. Detailed Implementation

[0038] The following embodiments of the invention are illustrated with respect to a specific type of drilling rig, wherein drilling is performed using an impact device in the form of a top hammer. The drilling rig can also be any other type of drilling rig, wherein drilling is performed using a hydraulic impact device for transmitting stress waves to the drill string to break the rock. The invention is also applicable to drilling rigs including other types of impact drilling rigs besides hydraulically driven drilling rigs, such as drilling rigs operated electrically or pneumatically.

[0039] Figure 1 A rock drilling rig 100 according to an exemplary embodiment of the present invention is shown, with regard to which an inventive method for determining the state of at least one joint of the drill string will be described. The drilling rig 100 is in the process of drilling, wherein the drilling has currently reached a depth x.

[0040] The rock drill 100 according to this example constitutes a surface drill rig; however, it should be understood that the drill rig may also be a percussion drill rig primarily used for, for example, underground drilling or for any other purpose. The rock drill rig 100 includes a carrier 101 that conventionally carries a cantilever 102. Furthermore, a feed beam 103 is attached to the cantilever 102. The feed beam 103 carries a carriage 104, which is slidably arranged along the feed beam 103 to allow the carriage 104 to travel along the feed beam 103. The carriage 104, in turn, carries an impact device 105, such as a drill bit, and also includes, for example, a rotating unit (not shown, but rotation is indicated by 117), so that the impact device 105 can travel along the feed beam 103 by sliding the carriage 104.

[0041] The impact device 105 is connected to the drilling tool, such as the drill bit 106 according to this example, via a drill string 107. The drill string may consist of a single drill rod, which is threadedly connected to the drilling machine, and the drill bit is threadedly connected to the drill rod. This is common, for example, in tunnel excavation. However, the drill string 107 is typically not composed of a single drill string, but rather of multiple drill rods. When drilling has proceeded a distance corresponding to the length of the drill rods, a new drill rod is threadedly connected to one or more drill rods already threaded together to form a drill string, thereby allowing drilling to proceed to another drill rod length before the new drill rod is threadedly connected to the existing drill rods. This is illustrated by drill rods 202 to 204, which are engaged together via threaded joints 206, 207. The drill bit 106 is engaged with drill rod 204 via threaded joint 208. Furthermore, the impact device 105 includes a drill shank (see [link to example]). Figure 2A An impact element in the form of an impact piston 115 strikes the drill shank, and the drill shank is connected to the drill string 202 via a threaded joint 205. Drill strings of the disclosed type can extend to virtually any desired length as drilling progresses. As the number of drill strings increases, the number of joints that may loosen and cause problems also increases. It should be noted that this invention is applicable to drill strings with any number of joints.

[0042] In use, the impact piston 115 of the impact device 105 repeatedly impacts the drill shank and thus the drill rod to transfer shock wave energy to the drill string 107, which in turn transfers it to the drill bit 106 and further into the rock to break it. In addition to providing rotation of the drill string and thus the drill bit 106 during drilling, the impact device 105 and / or the slide 104 also provide a feed force acting on the drill string 107 by being subjected to a force acting in the drilling direction, thereby pressing the drill bit 106 against the rock surface being drilled.

[0043] According to the example shown, the impact device 105, particularly the impact piston 115, is powered by pressurized hydraulic fluid supplied to the impact device by a hydraulic pump 116 arranged on the carrier 101 and a suitable hose 118. The carrier 101 also includes a hydraulic fluid tank 119 from which hydraulic fluid is drawn and returned via a hydraulic circuit that powers the impact device. Other hydraulic pumps may be present for supplying pressurized hydraulic fluid in one or more additional hydraulic circuits, such as, for example, damping circuits (see below).

[0044] Similarly, under normal circumstances, flushing fluids such as compressed air or a mixture of compressed air and water or any other suitable type of mixture can be directed to the drill bit 106 through channels (not shown) within the drill string 107, wherein compressed air can be supplied from the tank to the drill string 107 in a manner known per se, which is not shown herein.

[0045] The hydraulic pump 116 and other power consumers such as, for example, compressors and other hydraulic pumps are driven by a power source 111, which is, for example, an internal combustion engine such as a diesel engine or any other suitable power source such as, for example, an electric motor or a combination of power sources. Figure 1 Sensor 209 is also shown, which measures the stress wave introduced into the drill string by the impact piston 115 and the reflections that occur at various locations in the drill string and when the stress wave impacts the rock. As described above, sensor 209 can operate, for example, based on the principle of measuring changes in the magnetization of the drill string in response to stress waves traveling in the drill string, of which various such sensors are known in the art. For example, when performing the estimation according to the invention, a sensor as illustrated in any of the documents EP 2811110 A1, EP 3266975B1, WO 2007 / 082997 A1, US 6,640,205 B2, US 7114576B2, and WO 2017 / 217905A1 can be used.

[0046] The rock drilling rig 100 also includes a drilling rig control system, which includes at least one control unit 120. The control unit 120 is configured to control various functions of the drilling rig 100, such as controlling the drilling process. When the drilling rig 100 is manually operated, the control unit 120 can receive control signals from an operator, for example, located in an operator's compartment 114 (via operator-controlled devices such as joysticks and other devices requesting various actions), and wherein control signals, such as joystick deflections and / or manipulations of other devices caused by the operator, can be translated by the control system into appropriate control commands. The control unit 120 can, for example, be configured to request movements performed by various actuators such as cylinders / motors / pumps, for example, to manipulate the boom 102, feeder 103, and control the impact device 105, as well as various other functions. The described controls and other functions can alternatively be partially or fully autonomously controlled by the control unit 120.

[0047] The disclosed type of drilling rig may also include more than one control unit, such as multiple control units, each of which may be arranged to monitor and execute various functions of the drilling rig 100. However, for simplicity, it will be assumed below that the various functions are controlled by control unit 120. Such a control system can further utilize any suitable type of data bus to allow communication between the various units of the machine 100. When the drilling rig 100 is operated by an operator, various data may be displayed, for example, on one or more displays in the operator's cabin 114.

[0048] According to an embodiment of the invention, the control unit of the drilling rig, for example... Figure 1The control unit 120 performs the determination of the status of one or more joints of the drilling rig, but can also perform this determination at any other suitable location. Furthermore, as will be further explained and illustrated below, when it is determined that one or more joints of the drill string are loose, this can enable the drilling rig control system to take appropriate actions, such as adjusting or stopping drilling and / or providing appropriate notification to the drilling rig operator.

[0049] Figure 2A It shows according to Figure 1 The drill string. The impact device, i.e., the drill bit, is only partially shown in the illustration of the shank adapter 201. The impact piston strikes the shank adapter 201 to introduce stress waves into the drill string. The shank adapter 201 is threadedly connected to the first drill rod 202 via a threaded joint 205. Similarly, as described above, the drill rod 202 is threadedly connected to the second drill rod 203 via a joint 206, and so on, and wherein the drill string terminates at the drill bit 106, which impacts the rock surface to break the rock by the introduced shock waves.

[0050] As mentioned above, it is crucial to properly tighten the threads during drilling to avoid excessive wear on drill string components. Loose joints can also produce potentially harmful reflections, meaning that a significant portion of the introduced shock waves is reflected at the joint instead of being transmitted to the drill bit and ultimately to the rock to be broken. These reflections can be harmful not only to the drill string but also to the drilling rig's impact mechanism and other components. The ability to detect loose joints during normal drilling can reduce the chances of such adverse conditions going undetected for a period of time. However, as also mentioned above, the ability to detect loose joints is desirable not only during normal / conventional drilling. When drilling is complete, the drill string retracts from the drilled hole, during which time the components forming the drill string loosen from each other as the drill string is pulled out. However, during drilling, the joints become tightened to a degree that the rotation / torque applied by the rotary motor alone is insufficient to loosen the joints. Therefore, the following method is commonly used: the impact piston repeatedly strikes the drill string while the drill bit is not in contact with the rock. This is because such a process can loosen the joints.

[0051] Experienced drillers may be able to determine when repeated impacts on the drill string will sufficiently loosen all joints, allowing the drill string to retract directly. However, inexperienced drillers may apply impacts for longer than necessary, potentially resulting in excessive wear and possibly welding the threads together instead of thermal loosening caused by stress waves acting on already loosened threads. Alternatively, the applied impacts may be insufficient, resulting in all joints remaining unloosened. This can cause problems when retracting the drill string and require reconnecting the drill rig to the string for further loosening.

[0052] According to an embodiment of the invention, such problems can be mitigated by a system that can determine whether the drill string joint is sufficiently tightened for proper drilling or, as appropriate, sufficiently loosened to allow proper retraction of the drill string.

[0053] According to the implementation method, this determination can be performed individually for each connector, and Figure 2A The vertical axis t shows the time elapsed after the impact piston strikes the shank adapter (shown by impact surface A at time t = 0). It should be noted that time t = 0 can also be the time when the incident wave arrives at sensor 209, i.e., slightly after the actual initial contact point between the impact piston and the drill shank. As will be explained below, both the incident stress wave and the reflected stress wave are detected using sensor 209. However, according to embodiments of the invention, separate sensors can be used to detect the incident and reflected waves separately.

[0054] Then, signal processing is performed on the detected signal according to the following. However, to facilitate signal processing and reduce computation, it is not necessary to process the complete signal detected by sensor 209; processing only an appropriate portion of the detected signal is sufficient. This is in Figure 2A The diagram illustrates portions of the detected signal, denoted below by "cutouts" 206 to 210. These cutouts represent time intervals relating to the expected reflection at a particular joint. For example, cutout 206A represents a substantially immediate reflection occurring at joint 205, where the shank adapter 201 and drill pipe 202 are threaded together. Similarly, cutout 206A represents the joint between drill pipe 202 and drill pipe 203. Cutout 207A represents the joint between drill pipe 203 and drill pipe 204, and a final cutout 208A represents the joint from drill bit 106 to drill pipe 204. In addition to the cutouts shown, the incident wave can be measured starting at time t = 0. However, measuring the incident wave using time window 205A may be sufficient, as joint 205 is very close to the impact surface A.

[0055] As shown in the figure, since it takes time for the stress wave to propagate from the impact surface A through the drill string and be reflected at various reflection points along the drill string and travel back to the position of sensor 209, corresponding reflections occur at different time points.

[0056] The timing of evaluating a particular joint can be determined in various ways. For example, this can be determined directly by first using the distance from sensor 209 to one or more threads to be evaluated. Many parameters can influence this determination. For example, information such as the length of the drilled steel and the distance to the thread tip is required. Furthermore, the correct steel length is needed, i.e., the distance the stress wave travels in the steel from the impact of the impact piston.

[0057] However, such information is typically stored in the drilling rig control system. For example, the length of the shank adapter may be stored. The type of drill rod used is usually already input into the control system for use in other parts of the drilling rig control, and such data may include, for example, the length of the drill rod, the cross-sectional area and type of steel used in its manufacture. The propagation speed of stress waves in the steel can be accurately determined by the length of the steel, the Young's modulus of the drill steel, and the density of the drill steel. The speed can also be calibrated using knowledge of the drill steel length typically stored in the drilling rig control system, and the travel time can be determined by analyzing the arrival times of incident and reflected waves and / or multiple reflected waves and secondary incident waves (reflected waves that reach the drill shank and are reflected back to the rock, etc.) from different parts of the drill string. The speed can be determined based on the travel time.

[0058] Therefore, the propagation speed of the stress wave in the drill string can be directly determined using methods known per se. This also allows for the accurate determination of the precise "tick" of the sensor signal from sensor 209, which will be used to determine the state of the joint according to an embodiment of the invention. When determining the tick, the length of the joint is preferably also considered. Reflections will begin at the tip of the thread and will occur along the entire length of the thread. However, according to an embodiment of the invention, instead of using the tick, the complete signal from sensor 209 is used, where the expected arrival times of various reflections can still be determined in the same manner.

[0059] The following will refer to Figures 3 to 5 The description details the actual processing of sensor signals detected / received from sensor 209 to determine whether a joint is loose. Specifically, according to an embodiment of the invention, the stiffness of one or more joints being evaluated is estimated.

[0060] Regarding the first joint, namely the joint 205 where the drill shank is connected to the drill string 202, according to this example, the reflection from this joint will reach the sensor 209 before the complete stress wave is introduced into the drill string and propagates fully toward the drill bit 106. This is because the time required for the entire length of the stress wave to pass through, for example, the sensor 209 will depend on the length of the impact piston, and this time may be longer than, for example, the time required for the incident side of the stress wave to reach the first joint 205 and be reflected back to the sensor 209. Even if this is not the case, it may still occur, for example, depending on the specific location of the sensor 209. This is particularly true when the sensor is located near the joint between the drill shank and the first drill string. If the piston length is stored in the control system, this can be used to determine the pulse length of the incident stress wave.

[0061] Figure 3An exemplary sensor measurement is shown during a first time period when a stress wave is generated in the drill string. The impact piston begins to strike the drill shank at time t0, which causes compression of the drill string. The duration of the stress wave essentially corresponds to the time required for the stress wave to propagate through the length of the impact piston 115. This is schematically indicated by the time interval t1-t2 in the figure. Between times t1 and t2, there are also reflections caused by the joint between the drill shank and drill string 202, and these reflections are superimposed on the incident stress wave. The notch of this joint according to the example shown is determined as the time period t1-t2, and therefore the same as the notch of the incident wave. However, this depends on the sensor location according to this particular example. It should be understood that, in general, the incident and reflected waves can arrive at the sensor at different or partially overlapping or completely overlapping time intervals depending on the sensor location. This will also depend on the length of the drill shank. However, it may be advantageous to position the sensor near the first joint of the drill string. The notch of the subsequent joint, namely joint 206, is determined as the time period t3-t4. The notches of the remaining joints of the drill string ( Figure 3 A similar evaluation will be conducted (not shown in the image). Figure 3 The graph illustrates the stress waves from at least two impacts by the impact piston. This graph is also correlated with measurements performed in a laboratory environment. In real-world operation, the measured signals are typically much noisier. Furthermore, according to an embodiment of the invention, the piston impact trigger can be used to accurately determine the time point at which the piston impacts the impact surface A, thereby accurately determining the timing of the appropriate cut. According to an embodiment of the invention, this can instead be determined based on changes in the detected stress waves.

[0062] Figure 4A and Figure 4B Three exemplary stress wave measurements are shown, each representing the stroke of the impact piston. Figure 4A The cut of the first joint (i.e., the joint between drill shank 201 and drill rod 202) is shown, and thus the three different strokes / impacts of the impact piston are shown. Figure 4B The cut of the second joint (i.e., the joint between drill pipe 202 and drill pipe 203) is shown in a similar manner. Specifically, Figure 4A and Figure 4B The measured stresses of these joints as a function of time are shown, with time windows determined according to the above. The measured stress waves shown have been filtered according to the following. The measured signals may indeed have considerable noise. Note that the joints are represented as threads in the figures.

[0063] Figure 5 An exemplary method for determining the stiffness of a joint according to an embodiment of the present invention is shown. As described above and as follows... Figure 4A and Figure 4BAs shown, notches can be performed on each joint of the drill string. These joints can be evaluated sequentially or simultaneously, i.e., evaluated in parallel or as a new notch is generated. Evaluation can be continuous, i.e., each joint can be evaluated for each stroke of the impact piston (or, for example, each joint every X strokes). Notches for a specific thread are shown in step 501, where these notches can be performed based on stored and / or otherwise received signals 502, as measured by sensor 209. To perform the determination, the reflected wave (box 503 and as shown) is determined. Figure 4A and Figure 4B The representation of the incident stress wave (shown in box 504) and the representation of the incident stress wave are shown. Regarding the incident stress wave, this can be determined by a separate cut, determined by the distance from the impact surface of the impact piston striking the drill shank to the location of sensor 209, or, for example, by a cut that already exists in time period t1-t2, which substantially covers the incident stress wave. This determination is performed for each joint of the drill string to be evaluated.

[0064] If the first thread is close to the sensor, as in this example, and is also loose, the incident wave will mix with the reflected wave from the loose joint. This can be compensated for, especially for obtaining accurate results from joints further away on the drill string.

[0065] Such compensation can be performed by adjusting the signal to remove reflection from the first joint, or by using a stored reference signal from the same combination of the handle and piston when the joint is tightened, such that the reflection can be estimated as a difference relative to that reference. This reference signal can be predetermined and stored in the control system. Alternatively, the reference signal can be stored from a previous impact where the joint is considered to be tightened. Sensors or combinations of sensors capable of separating the incident and reflected waves from each other can also be used. This can be performed, for example, by measuring the deflected stress wave using individual sensors or individual sensor elements of a single sensor, allowing the incident and reflected waves to be solved from the two measurements.

[0066] In step 505, the reflected wave is filtered and offset adjusted. Regarding filtering, this can be performed in any suitable manner, for example, to remove ripples caused by reflections from other loose joints and / or irregularities in the drill string. This can be performed, for example, by using moving average filtering, but can also be performed by filtering in any other suitable manner, such as finite impulse response (FIR) filtering and / or infinite impulse response (IIR) filtering. In addition to filtering the reflected wave in step 505, the reflected wave can also be offset adjusted to remove any offset in the signal that is not caused by a specific reflection being positively evaluated. This can be performed by subtracting a reference offset or by using measurements taken from the start of the cut time window as a reference.

[0067] Typically, the reference offset can be determined in various ways. For example, sensor signals representing the strokes on a drill string with the same drill shank and drill bit, and possibly drill pipe, can be stored in the control system. The offset can be determined and used as a reference, which can then be subtracted from the measurement signal. Alternatively or additionally, sampling can be performed at the beginning, for example, at the beginning of the stress wave when the incoming wave is measured, or at the beginning of the time period in which the analysis is performed. A reference offset from a previous stroke, i.e., a reference offset already stored when the previous stroke was measured, can also be used. The offset can be compensated for before and after filtering to remove any residual offset after filtering. Furthermore, it may be necessary to consider whether the first joint, i.e., the joint between the drill shank and the first drill pipe, is loose, and to compensate for this when analyzing the reflection from the joint between the first and second drill pipes.

[0068] In step 506, the incident wave signal is filtered in a similar manner, for example, using a moving average filter or any other suitable type of filter. Furthermore, any offsets are removed, which can be determined in a similar way. The incident wave can also be scaled to a level corresponding to the level of the reflected wave. This scaling can be performed, for example, because the cross-sectional area of ​​the joint may be larger than that of the drill pipe, thus affecting the level of the reflected wave. This is in Figure 2B The diagram illustrates that, Figure 2B The different cross-sectional areas of connector 206 are shown, namely A. joint (Cross-sectional area of ​​the joint) and A rod (Cross-sectional area of ​​the rod). Then the scaling factor. It can be applied to incident waves to obtain appropriate scaling related to reflected waves.

[0069] In step 507, the force exerted by the joint when subjected to the incident wave is estimated, for example, according to the following equation:

[0070] F = A rod (σ inc +σ ref (Equation 1)

[0071] in

[0072] A rod The area described above is that of the drill pipe. Since the type of drill pipe, etc., is used for general control of the drilling rig, the control system typically knows this area.

[0073] σ inc It is a filtered representation of the incident wave, as determined in step 506, that is, the stress wave introduced into the drill steel by the impact piston.

[0074] σ refIt is a filtered representation of the reflected wave from the connector being evaluated, and is determined in step 505.

[0075] These representations preferably have a corresponding time length.

[0076] In step 508, the velocity v as the stress wave propagates through the drill steel is estimated. thread This estimate of the propagation speed can be estimated as follows:

[0077]

[0078] in

[0079] c is the velocity of sound in the cobalt steel, which can be determined directly, for example, by considering the Young's modulus of the cobalt steel. p is the density of the cobalt steel.

[0080] These parameters can be stored in the drilling rig's control system for various drill pipes in case of parameter changes.

[0081] In step 509, the estimated velocity is integrated to obtain the displacement, which is a measure of the compression (or extension) of the joint when subjected to the incident wave.

[0082] d=∫v thread dt (Equation 3)

[0083] The stiffer the joint, the smaller the displacement d relative to the applied force. Therefore, according to an embodiment of the invention, the degree of compression of the joint and the force required to complete the compression (or extension, which may be the case), i.e., the longitudinal displacement of the joint, are used to determine the representation of the joint's stiffness.

[0084] This is Figure 6A and Figure 6B As shown in, Figure 6A and Figure 6B The calculated force is plotted relative to the calculated displacement. Figure 6A and Figure 6B They represent about Figure 4A and Figure 4B The calculated value of the measurement.

[0085] Therefore, stiffness can be defined as the change in force relative to concurrent displacement, i.e. As long as the estimated stiffness exceeds, for example, a threshold This confirms that the connector has been fully tightened.

[0086] This is Figures 6A to 6B As shown in, Figures 6A to 6B The dashed lines 601 and 602 represent the threshold values, respectively. Stiffness above a threshold, i.e., stiffness above the threshold line, is considered sufficiently tightened, while stiffness below the threshold line is considered to indicate a loose joint. Therefore, regarding... Figure 6A In the example, solid lines indicate a stroke where the joint is considered to be firmly tightened, while dashed and dotted lines indicate a loose joint.

[0087] about Figure 6B In the example, solid lines and dashed lines are considered to represent tightened joints, while dashed lines are considered to represent loose joints.

[0088] When in Figure 5 When the stiffness of a specific joint or any joint (which may be as appropriate) is determined in box 510, this can be indicated to the drill rig operator or used for, for example, the automatic control of the drill rig in box 511 in any suitable manner. The stiffness of the drill string joints can be continuously estimated so that a signal indicating, for example, the presence of a loose joint can be generated whenever deemed necessary. For example, there may be indicators, such as lights or other types of indicators on the display, indicating whether one or more joints are considered to be at least partially loose because the joints exhibit insufficient stiffness.

[0089] This can then be used by the control system in automated drilling or by the operator, allowing the control parameters used to control drilling to be adjusted automatically or manually as deemed necessary. During normal drilling, it will be sufficient to indicate whether any joint in the drill string is at least partially loose or allows the operator to take necessary actions if required. For example, this could include adjusting the drilling control parameters, for instance, by increasing and / or decreasing any of the control parameters impact pressure, feed pressure, and rotational pressure.

[0090] In the event of drill string retraction, alternatively and / or additionally, indicators may exist to show whether all joints have been loosened. Estimates of joint stiffness can also be used in automated drilling, where the rig control system can adjust drilling control parameters in response to estimates of joint condition. Similarly, when the drill string is to be retracted, the control system can apply a degree of impact to precisely loosen the joints while avoiding excessive impact.

[0091] According to the present invention, a method is therefore provided for accurately estimating the stiffness of a joint using reflected waves, which themselves may be difficult to analyze, particularly during observation. Figures 4A to 4B The curves are obvious, even though these curves have been filtered and offset removed.

[0092] Based on the example above, an estimation has been performed to determine whether the joint is tight or loose. According to embodiments of the invention, the presentation to the user or control system controls may also be, for example, the number of loose threads per specific number of impacts, expressed as a percentage. The determination according to the invention can be arranged to begin at the start of drilling. The results of the estimation of the joint's state can also be stored, for example, in memory 512, to allow the use of historical data.

[0093] This invention also allows for different thresholds for the increase in force relative to the change in displacement. This can be used to detect whether one or more joints are about to loosen, allowing appropriate action to be taken before the joints actually become loose. Furthermore, the thresholds can be different for different joints in the drill string.

[0094] Figure 7 It shows Figure 2A Various connectors ( Figure 7 The figure shows an exemplary estimate of the stiffness of the thread (represented in the figure) over time. It illustrates the estimate under 120 consecutive or discontinuous (whichever may be the case) impacts on the piston. For any X impacts, the measurement can be arranged to be performed once for each thread. The figure shows a level 701 representing a threshold above which the joint is considered securely tightened. As can be seen from the figure, all joints are estimated to be fully tightened throughout the entire measurement period shown.

[0095] Figure 8 With similar Figure 7 The way shown Figure 2A Examples of estimates of the stiffness of various joints over time. Figure 8 The estimates for approximately 300 impacts are shown. Based on... Figure 8 For example, for all impacts, joint 1 was substantially fully tightened. The same was true for joint 2, while for most impacts between 3470 and 3600, thread 3 was loose, and joint 4 was largely loose between 3560 and 3600. Moving forward from impact 3600, for virtually all joints, the joints were tightened. This is likely because the drilling rig control system or operator has adjusted one or more drilling control parameters based on the estimated stiffness of the monitored joints, resulting in the joints being securely tightened again. When the drilling rig control system automates the control parameters, it can estimate the stiffness immediately after adjustment, thus ensuring properly tightened joints.

[0096] This invention can be used with virtually any type of drilling rig, where hydraulic percussion drilling is combined with joints that may loosen during drilling. Similarly, this invention is applicable to any other type of percussion drilling technique. This invention applies to underground drilling rigs as well as drilling rigs operating on the surface.

Claims

1. A method for determining the state of at least one joint (205, 206, 207, 208) of a drill string (107) of a drilling rig (100), the drilling rig (100) comprising: An impact device (105) includes an impact element (115) for introducing a shock wave into the drill string (107); and a sensor (209) for sensing a stress wave in the drill string (107) caused by the impact of the impact element (115), the method comprising performing the following operations when the impact element (115) introduces a stress wave into the drill string (107): Determine the representation of the incident stress wave caused by the impact element (115); Determine the representation of the reflected stress wave, which represents the reflection of the incident stress wave upon reaching the at least one joint (205, 206, 207, 208); The stiffness of the at least one joint (205, 206, 207, 208) is estimated by estimating the force exerted on the at least one joint (205, 206, 207, 208) by the incident stress wave and the displacement caused by the force. Based on the estimated stiffness, a signal representing the state of the at least one joint (205, 206, 207, 208) is generated.

2. The method according to claim 1, further comprising: By multiplying the sum of the representations of the incident stress wave and the reflected stress wave by the cross-sectional area of ​​the drill string (107) component ( , The force is estimated using this method.

3. The method according to claim 1 or 2, further comprising performing the following operations before estimating the stiffness of the joint: At least one of the representations of the incident stress wave and the reflected stress wave is filtered.

4. The method according to any one of claims 1 to 3, further comprising: Before estimating the stiffness of the joint, offsets in the representation of the incident stress wave and / or the reflected stress wave, which are related to the signal level caused by other reflections in the drill string (107), are removed.

5. The method according to any one of claims 1 to 4, further comprising: The stiffness is estimated as the change in force exerted on the at least one joint (205, 206, 207, 208) by the incident stress wave relative to the displacement of the joint caused by the force.

6. The method according to claim 5, further comprising: When the change in force relative to the change in displacement exceeds a threshold, it is determined that the joint is tightened.

7. The method according to any one of claims 1 to 6, further comprising: Monitor the estimated stiffness of at least one of the joints (205, 206, 207, 208), and One or more drilling control parameters are adjusted by means of the drilling rig control system based on the estimated stiffness of the at least one joint (205, 206, 207, 208) being monitored.

8. The method according to any one of claims 1 to 7, further comprising: Estimate the stiffness of multiple or all of the joints (205, 206, 207, 208) of the drill string (107).

9. The method according to any one of claims 1 to 8, further comprising performing the following operation when all joints (205, 206, 207, 208) are to be loosened: By estimating the stiffness of the joints (205, 206, 207, 208), it is determined whether all joints (205, 206, 207, 208) are loose, and A signal is generated when it is determined that all connectors (205, 206, 207, 208) are loose.

10. The method of claim 9, further comprising: The impact element (115) is controlled by the drilling rig control system to apply an impact to the drill string (107). The stiffness of the joints (205, 206, 207, 208) is continuously estimated to determine whether all joints (205, 206, 207, 208) are loose, and Once it is determined that all joints (205, 206, 207, 208) are loose, stop applying impact to the drill string (107).

11. The method according to any one of claims 1 to 10, further comprising determining the state of the particular joint by estimating when the sensor (209) is able to detect the reflection of the incident stress wave originating from the particular joint in time.

12. The method according to any one of claims 1 to 11, further comprising performing the following operation when the first connector (205) is a certain distance away from the sensor (209) such that the incident stress wave and the reflected stress wave are mixed: The representation of the incident stress wave is compensated for by the reflection, so that the representation of the incident stress wave is effective in estimating the stiffness of the joints (206, 207, 208) further away from the sensor (209).

13. The method according to any one of claims 1 to 12, further comprising: The representation of the incident stress wave is determined using a first sensor element, and the representation of the reflected stress wave is determined using a second sensor element.

14. A computer program product comprising instructions that, when executed by a computer, cause the computer to perform the method according to any one of the preceding claims.

15. A computer-readable medium comprising instructions that, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 13.

16. A system for determining the state of at least one joint (205, 206, 207, 208) of a drill string (107) of a drilling rig (100), the drilling rig (100) comprising: An impact device (105) includes an impact element (115) configured to introduce a shock wave into the drill string (107); and a sensor (209) configured to sense a stress wave in the drill string (107) caused by the impact of the impact element (115), the system being characterized in that the system is configured to operate as follows when the impact element (115) introduces a stress wave into the drill string (107): Determine the representation of the incident stress wave caused by the impact element (115); Determine the representation of the reflected stress wave, which represents the reflection of the incident stress wave upon reaching the at least one joint (205, 206, 207, 208); The stiffness of the at least one joint (205, 206, 207, 208) is estimated by estimating the force exerted on the at least one joint (205, 206, 207, 208) by the incident stress wave and the displacement caused by the force. Based on the estimated stiffness, a signal representing the state of the at least one joint (205, 206, 207, 208) is generated.

17. A rock drilling rig (100), characterized in that, It includes the system according to claim 16.

Images