Methods and systems for detecting loose joints in drill strings

Abstract

This invention relates to a method for determining the state of joints (134, 135, 136, 137) connecting a first drill string assembly and a second drill string assembly (105, 106, 131, 132, 133). A drilling rig (100) includes a rotating unit (109) for rotating a drill string (107) and a means for determining the torque applied by the rotating unit. When the joints (134, 135, 136, 137) are released, joint release mechanisms (140, 300), separate from the rotating unit (109), apply a joint release torque acting on the drill string (107). The method includes applying torque in the joint release direction by means of the rotating unit (109) and applying the joint release torque acting on the drill string by means of the joint release mechanisms (140, 300). The torque applied by the rotating unit is monitored during the application of the joint loosening torque, and the joints (134, 135, 136, 137) are determined to be loosened based on the monitored representation of the torque applied by the rotating unit (109).

Description

Technical Field

[0001] This invention relates to mining, and more particularly to a method and system for detecting whether a drill string joint has become loose. The invention also relates to a computer program for implementing the method according to the invention, as well as a system and drilling rig. Background Technology

[0002] Rock drilling rigs can be used in many applications. For example, they can be used for tunnel excavation, open-pit mining, underground mining, rock reinforcement, well drilling, and 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 breaking of rock is typically performed by a drill bit that contacts the rock, which is usually connected to the drilling rig via a drill string. Drilling can be accomplished in various ways, and can be, for example, percussion, in which the impact elements of the drilling rig repeatedly strike the drill bit. The drilling rig can be directly connected to the drill bit, such as in DTH / ITH drilling, or alternatively connected to the drill bit via the drill string to transmit impact pulses in the form of shock / stress waves to the drill bit and further into the rock. Percussion drilling can be combined with rotary drilling to achieve drilling in which the ball teeth or inserts of the drill bit strike new rock with each stroke, thereby increasing drilling efficiency. Rotary drilling can also be used.

[0004] When drilling longer holes, multiple drill rods can be connected together using joints to extend the drill string, thus allowing the desired hole length to be drilled. Drill rods are typically threaded, and therefore, as drilling progresses, additional drill rods are added by threading them onto the existing drill string. After drilling is complete, i.e., after a specific hole has been drilled, the drill string is retrieved from the borehole one by one, as the drill string is pulled back and the drill rods are disconnected from each other.

[0005] Drill pipe joints can be tightened so securely during drilling that high release torque may be required to loosen them, thereby allowing the drill pipe to separate from each other and be removed from the drill string. Various solutions exist for achieving joint loosening, including, for example, the use of joint loosening mechanisms. These mechanisms apply the loosening torque by means of leverage acting on the drill string. However, this type of solution can cause excessive wear on drill string components. Summary of the Invention

[0006] The object of this invention is to provide a method and system that can be used in the loosening of a joint to avoid excessive wear on components during the joint loosening process. According to embodiments of the invention, a method and system that can increase the available loosening torque when loosening a joint is also provided.

[0007] According to the present invention, a method is provided for determining whether a joint of a drill string of a drilling rig has been loosened by attempting to loosen the joint, the joint connecting a first drill string component and a second drill string component. The drilling rig includes a rotating unit for rotating the drill string during drilling and a means for determining a representation of the torque applied to the drill string by the rotating unit. A joint loosening mechanism, separate from the rotating unit, is configured to apply a joint loosening torque acting on the drill string when the joint is loosened.

[0008] The method includes, when the drill string joint is loosened:

[0009] A torque is applied in the direction of joint release using a rotating unit;

[0010] The joint release mechanism applies a joint release torque to the drill string;

[0011] During the application of joint loosening torque by means of the joint loosening mechanism, the representation of the torque applied by the rotating unit is monitored;

[0012] The presence or absence of a loose joint is determined based on the monitored torque applied by the rotating unit; and

[0013] A signal indicating that the connector has been released is generated when the above determination indicates that the connector has been released.

[0014] The rotating unit can be part of the drilling machine of a drilling rig or constitute a separate unit from the drilling machine. According to an embodiment of the invention, the drilling machine includes an impact element for introducing shock waves into the drill string during drilling. According to an embodiment of the invention, the drilling machine performs drilling solely by rotation.

[0015] Properly tightening the joints is essential for efficient drilling. Threaded joints are typically tightened during drilling, for example, due to the shock waves passing through them during the drilling process.

[0016] However, at some point, the tightened joint will be loosened and the drill string components—the rotary unit, drilling machine, drill pipe, and / or drill bit—will separate from each other. For example, after drilling, the drill string retracts and the drill pipes separate from each other. However, this also applies when the length of the drill pipe has been drilled and additional drill pipes are added to the drill string. In some cases, the joint loosening torque available through the rotary unit is sufficient to loosen the joint. In this case, it is sufficient to clamp the drill string downstream of the joint using a suitable gripping device to allow the rotary unit to apply the joint loosening torque. However, during drilling, the joint may become so tightly tightened that it can only be loosened with the assistance of the rotary unit.

[0017] In this case, a joint release mechanism different from the rotating unit can be used. This joint release mechanism can be, for example, but not limited to, a so-called disconnecting tool, which can also be referred to as a breaking table, crushing table, or disconnecting table, or a breaking tool. Other names for this type of solution may also be used. For simplicity, the term disconnecting tool will be used below. A disconnecting tool, or any other solution, is included in this invention and is capable of firmly clamping the components connected by the joint by means of a gripping device such as a jaw, while applying rotational motion to one of the drill string components connected by the joint through leverage, for example, by a hydraulic cylinder acting on the gripping jaw of one of the joint components. The problem with this solution is that it is impossible to detect whether the joint has actually been released by attempting to release the joint, or whether the gripping device of the joint release mechanism has slid on the drill string component without properly clamping it, resulting in no or very little release torque actually acting on the joint. This leads to a solution in which the joint release torque is applied repeatedly to ensure that the joint is released before the connected components are unscrewed and separated.

[0018] However, this solution leads to excessive wear on both the drill string components and the joint release mechanism. Furthermore, repeated release attempts are time-consuming.

[0019] According to an embodiment of the invention, such a problem can be alleviated by a method in which torque is applied using a joint loosening mechanism to detect whether the joint is actually loosened.

[0020] This is achieved by applying torque in the joint-loosening direction using the drilling rig's rotating unit, such as a rotary motor, before applying the joint-loosening torque using the joint-loosening mechanism. Before the torque is applied via the rotating unit, as seen from the rotating unit, the drill string can be locked at least downstream of the joint to prevent rotation. Therefore, the applied torque typically does not cause actual rotation of the drill string at this stage.

[0021] Then, during the application of the joint loosening torque by means of the joint loosening mechanism, the representation of the torque applied by the rotary unit is monitored, and based on the monitored representation of the torque applied by the rotary unit, it is determined whether the joint has been loosened by this action. When this determination indicates that the joint has been loosened, a signal indicating that the joint has been loosened is generated. In this way, the rotary unit is used to determine whether the joint has actually been loosened by the joint loosening mechanism. If the joint is loosened on the first loosening attempt, this can be detected, so that no further attempts are needed and excessive wear is avoided, saving time. Alternatively, the joint can be unscrewed to separate the drill string components from each other. In the case that the rotary unit is a hydraulic rotary unit, the representation of the torque applied by the rotary unit can be the hydraulic pressure applied to the rotary unit.

[0022] According to an embodiment of the invention, the torque applied by the rotating unit is monitored while the loosening torque is applied by the joint loosening mechanism, and the joint is determined to be loosened when a predetermined change in the monitored torque applied by the rotating unit is detected. If the joint is loosened, the torque applied by the joint loosening mechanism will cause the drill string to rotate, and this rotation will affect the torque provided by the rotating unit. When a predetermined change is detected, it can be concluded that the joint has been successfully loosened. In the case that the rotating unit is a hydraulic rotating unit, changes in the pressure acting on the rotating unit can be monitored.

[0023] According to an embodiment of the invention, a loosening of the joint is determined when the monitored value of the torque applied by the rotating unit is below a predetermined threshold. That is, a loosening of the joint is only determined if a sufficiently large decrease in the value of the torque, such as pressure, applied by the rotating unit is detected. In cases where only a small rotation of the drill string is achieved by the joint loosening mechanism and the joint is not thus sufficiently loosened, this may not cause a sufficiently large decrease and therefore will not be detected as a loosening of the joint.

[0024] According to an embodiment of the invention, the rotation unit is configured with a first rotational speed, which is lower than the rotational speed applied by the joint release mechanism when torque is applied to the drill string. In this way, when the drill string is rotated by the joint release mechanism, the rotational speed will exceed the set rotational speed of the rotation unit, such that the torque supplied to the rotation unit will be insufficient for the current rotational speed of the drill string and thus reduced.

[0025] According to an embodiment of the invention, the joint release torque applied by means of the rotating unit acts together with the joint release mechanism such that the total release torque applied to the drill string exceeds the torque applied by the joint release mechanism at least before the drill string begins to rotate. This provides a solution for generating a higher total release torque, which increases the likelihood of releasing the joint.

[0026] According to an embodiment of the invention, when the torque applied by the rotating unit indicates that the joint is still tightened after the joint loosening torque is applied by the joint loosening mechanism, the application of torque by the rotating unit and the application of joint loosening torque by means of the joint loosening mechanism are repeated. One or more additional attempts can increase the probability of loosening the joint, but these additional attempts are only used if the conclusion is reached that the joint has not been loosened, and only to the extent of that conclusion. Therefore, repeated attempts are only used when there is a motivation.

[0027] According to an embodiment of the invention, when the torque applied by the rotating unit and the joint loosening torque applied by means of the joint loosening mechanism have been repeated a predetermined number of times without confirming that the joint has been loosened, an alarm signal indicating a fault is generated. In this way, the drilling rig control system or operator can be aware that the joint loosening has not been successful and can take appropriate action.

[0028] According to an embodiment of the present invention, the joint release mechanism includes a first clamping device and a second clamping device, the first clamping device being used to hold the drill string in a releasable position upstream of the joint in relation to the rotating unit, i.e., on the rotating unit side of the joint to prevent rotation, and the second clamping device being used to hold the drill string in a releasable manner downstream of the joint in relation to the rotating unit.

[0029] According to an embodiment of the invention, the joint release mechanism includes a lever device for applying torque to the drill string through the gripping of a first clamping device. This provides a solution capable of delivering high release torque.

[0030] According to an embodiment of the invention, when the monitoring indicator, representing the torque applied by the rotating unit, indicates the loosening of the joint, the gripping of the first clamping device is released. This allows the joint to be unscrewed by means of the rotating unit so that the drill string components can be released from each other after the joint is loosened.

[0031] According to an embodiment of the invention, the rotating unit is hydraulically driven and includes, for example, a rotary motor. In this case, the torque applied by the rotating unit can be monitored by monitoring the hydraulic pressure of the rotating unit. The pressure can be monitored by means of one or more pressure sensors. The rotating unit can also be controlled to be set to a predetermined rotational speed, and a rotational pressure acting on the rotating unit in the unscrewing direction can be applied before the torque is applied by the joint loosening mechanism. The rotational pressure can be continuously increased until at least a predetermined rotational pressure is reached, after which the torque can be applied by the torque loosening mechanism.

[0032] According to an embodiment of the invention, whether the joint is loosened is determined based on the monitored change in rotational pressure, particularly based on the presence of at least a predetermined pressure drop while the loosening torque is applied by the joint loosening mechanism.

[0033] According to an embodiment of the invention, when it is determined that the joint has been loosened during the application of torque, the application of the joint loosening torque by means of the joint loosening mechanism is immediately stopped. Therefore, the joint loosening mechanism can only be used precisely to loosen the joint to the required degree. This further reduces wear on, for example, drill string components and the joint loosening mechanism.

[0034] The method according to the invention can be performed partially or entirely by means of the drilling rig control system.

[0035] Other features and advantages of the invention are illustrated in the detailed description of the exemplary embodiments set forth below and in the accompanying drawings. Attached Figure Description

[0036] Figure 1 An exemplary drilling rig that can utilize embodiments of the present invention is illustrated;

[0037] Figure 2 An exemplary method according to an embodiment of the present invention is illustrated;

[0038] Figure 3 An exemplary joint release mechanism according to an embodiment of the present invention is illustrated;

[0039] Figure 4 An exemplary hydraulic circuit of a rotating unit used according to an embodiment of the present invention is illustrated.

[0040] Figure 5 The illustration shows the clamping of a drill string via a joint release mechanism according to an embodiment of the present invention. Detailed Implementation

[0041] Embodiments of the invention will be illustrated below with reference to specific types of drilling rigs, wherein drilling is performed using an impact device in the form of a downhole (DTH) / in-well (ITH) hammer. However, the invention is also applicable to other types of drilling rigs, wherein, for example, a rotary unit comprising or including a rotary motor is used to rotate the drill string during drilling. The drilling rig can also be any other type with or without an impact device, wherein a rotary unit is used to rotate the drill string during drilling, and wherein a release torque is applied to the drill string using leverage. For example, the drilling machine and the rotary unit can be arranged relative to the drill bit at opposite ends of the drill string, such as on a bracket of the feed beam, and the drilling machine and the rotary unit can also form an integrated unit providing both impact and rotation or an integrated unit for drilling solely by rotation. The invention is also applicable to other types of drilling machines besides hydraulically driven drilling machines, such as drilling machines operated by electrical or pneumatic devices.

[0042] Figure 1 A rock drilling rig 100 according to an exemplary embodiment of the present invention is illustrated, and an inventive method for determining the state of at least one joint of the drill string will be described with respect to the rock drilling rig 100. The drilling rig 100 is in the process of drilling, wherein the drilling has currently reached a depth x.

[0043] The rock drilling rig 100 according to this example constitutes an open-pit drilling rig; however, it should be understood that the drilling rig may also be of the type primarily intended for, for example, underground drilling, or for any other purpose. The rock drilling 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 bracket 104, which is slidably arranged along the feed beam 103 to allow the bracket 104 to travel along the feed beam 103. The bracket 104, in turn, carries a rotating unit 109, wherein rotation is indicated by 117. The rotating unit 109 is connected by means of a drill string 107 to an impact device, i.e., a drilling machine, in the form of a downhole (DTH) hammer 106. The rotating unit 109 can provide rotation in two directions of rotation. Therefore, the rotating unit 109 can travel along the feed beam 103 by sliding the bracket 104. In addition to rotating the drill string 107, the rotating unit 109 also provides a feed force acting on the drill string 107, thereby pressing the drill bit 108 against the rock surface being drilled.

[0044] As its name suggests, the DTH hammer (impact device) 105 operates by penetrating the borehole at the end of the drill string 107. The impact piston (not shown) of the DTH hammer 105 strikes a drill tool such as the drill bit 106 to transfer shock wave energy to the drill bit 106 and further into the rock to break it. The DTH hammer is useful, especially because the drilling rate is not significantly affected by the length / depth of the borehole being drilled. Therefore, the rotation provided by the rotating unit 109 transmits rotational energy via the drill string 107 to the hammer 105 and thus to the drill bit 106.

[0045] Drill string 107 may include a single drill rod threadedly connected to rotary unit 109 and impact device 105 (the drill bit is also threadedly connected to impact device 105). However, drill string 107 typically does not include a single-piece drill string, but rather comprises multiple drill rods. When drilling has advanced a distance corresponding to the length of the drill rods, a new drill rod is threadedly connected to one or more drill rods that are already threaded together to form a drill string, thereby allowing drilling to advance another drill rod length before the new drill rod is threadedly connected to the existing drill rods. Drill rods of the disclosed type can extend substantially to any desired length as drilling progresses. This is illustrated by drill rods 131 to 133, which are joined together by threaded joints 135, 136. It should be noted that the invention is applicable to drill strings having any number of joints. Drill bit 106 is threadedly connected to drill rod 133 by means of threaded joint 137. Furthermore, impact device 105 includes an impact element in the form of an impact piston acting on drill bit 106.

[0046] During use, the impact piston of the impact device 105 repeatedly strikes the drill bit 106 to transfer shock wave energy into the rock to break it. The rotating unit 109 provides rotation of the drill string 107 during drilling to ensure that the drill bit inserts of the drill bit 106 are indexed between the strokes of the impact piston, thereby preventing the drill bit inserts from repeatedly striking the rock in the same manner.

[0047] According to the illustrated example, the rotating unit 109 is powered by pressurized hydraulic fluid supplied to the impact device by one or more hydraulic pumps 116 arranged on the carrier 101 and suitable hoses 118. The carrier 101 also includes a hydraulic fluid tank 119 from which hydraulic fluid is drawn and returned to power the rotating unit 109 using a hydraulic circuit. Additional hydraulic pumps may be present to provide pressurized hydraulic fluid in one or more additional hydraulic circuits, such as damping circuits.

[0048] Furthermore, the DTH hammer 105 is driven by compressed air, and for this reason, the compressed air is guided to the hammer 105 through channels inside the drill string 107, wherein the compressed air is supplied from the housing 115 to the drill string 107 via suitable couplings and hoses or other suitable devices known per se and therefore not shown herein. The compressed air is generated by a compressor 110, which can inflate the housing 115, from which the compressed air is supplied to the drill string. Exhaust gas from the DTH hammer 105 can be discharged through holes in the drill bit for the purpose of removing drilling residue from the borehole, which is also the usual practice.

[0049] Hydraulic pump 116, compressor 110 and other power-consuming devices, such as other compressors and other hydraulic pumps, are driven by power source 111, which is, for example, an internal combustion engine, such as a diesel engine or any other suitable power source, such as an electric motor or a combination of power sources. Figure 1 Also illustrated is a pressure sensor 112 used to measure the pressure of the hydraulic circuit that powers the rotating unit 109. It should be understood that various other pressure sensors and other types of sensors are used in conjunction with the drilling rig of the disclosed example. For simplicity, such sensors are not illustrated.

[0050] 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 requesting various actions, and other devices, wherein the 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 and rotary unit 109, 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.

[0051] The disclosed type of drilling rig may also include more than one control unit, such as multiple control units, wherein each control unit 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 may further utilize any suitable type of data bus to allow communication between the various units of the drilling rig 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 compartment 114.

[0052] According to an embodiment of the present invention, the loosening of the joint according to the embodiment of the present invention is controlled by the control unit of the drilling rig, for example... Figure 1 The control unit 120 performs this function partially or completely.

[0053] Regarding the loosening of the connector, Figure 1 The drilling rig 100 also includes Figure 1 The connector release mechanism is schematically indicated by 140, and will be referred to below. Figure 3 A more detailed description of the joint release mechanism is provided.

[0054] As described above, when drilling is complete, the drill rod retracts from the borehole, wherein during retraction, the components forming the drill string loosen from each other as the drill string is pulled out. Similarly, when the length of the rod has been drilled, the rotating unit detaches from the drill rod that was just drilled, allowing another drill rod to be added to the drill string.

[0055] However, during drilling, the joint can be tightened to the point that the rotation / torque applied by the rotary motor is insufficient to loosen the joint. Therefore, as discussed above, a method is typically used in which a joint loosening mechanism or breaking mechanism, such as a disconnecting tool, is used to break the joint, so that even if the joint is loosened, the drill pipes, for example, threaded together during drilling, can separate from each other if the rotary motor cannot provide sufficient joint loosening torque (i.e., the torque applied in the joint loosening direction) to break the joint. The joint breaking mechanism 140 is referred to as a disconnecting tool in this specification, but as discussed, it can also have various other names and designs.

[0056] As discussed above, it may be impossible to determine whether the disconnecting tool's disengagement action actually loosened the connector.

[0057] Figure 2 An exemplary method according to an embodiment of the present invention is illustrated, by means of which it is possible to detect whether a joint loosening action has actually loosened the joint. The method begins in step 201, in which it is determined whether the joint has been loosened. In the case of fully automated controlled drilling, this determination can be performed automatically by the drilling rig control system. Figure 2 The method can also be initiated, for example, by an operator requesting the initiation of joint detachment. According to embodiments of the invention, the method may include the step of positioning the drill string, particularly the joint to be detached, in a suitable location for properly completing the detachment. This positioning of the drill string can be performed by an operator or automatically by the drilling control system. Specifically, this positioning relates to the positioning of the joint relative to the disconnecting tool.

[0058] The transition from step 201 to step 202 may depend, for example, on an indication that the drill string is actually in a position for performing the joint loosening according to an embodiment of the invention, wherein such an indication may be provided by the drilling rig control system or, for example, implicitly by the operator requesting the method. According to an embodiment of the invention, the method remains in step 201 as long as the joint is not loosened, and continues to step 202 when the joint is loosened.

[0059] When it is determined in step 201 that the joint will be loosened and the drill string according to an embodiment of the invention is in a position for loosening the joint, the joint loosening mechanism and disconnecting tool according to this example are prepared in step 202 for loosening the joint. Figure 3 The diagram illustrates an exemplary disconnect tool 300. As mentioned above, in Figure 1 The diagram also schematically illustrates the disconnect tool represented by 140. Figure 3The disconnect tool 300 is intended for illustrative purposes only, and it should be recognized that the joint release mechanism can have a variety of different designs and configurations. However, what is common to this design and configuration of the joint release mechanism is that it is provided with a device for clamping the drill string and providing torque by means of leverage.

[0060] according to Figure 3 In an exemplary embodiment, the disconnecting tool 300 includes clamping devices 302, 303, 304, and 305 for clamping the drill string. Clamping devices 304 and 305 clamp the drill string to one side of the joint to be released, thus connecting one drill string component via the joint, while clamping devices 302 and 303 clamp the drill string to the other side of the joint to be released, thus connecting another drill string component. Each of clamping devices 302 to 305 includes, for example, a clamping device 306 in the form of a jaw. It should be noted that the clamping devices and therefore the jaws are only visible in the figures for clamping element 303. The clamping device 306 is frictionally connected to the drill string component when pressed against the drill string, wherein this force can be applied, for example, by means of a hydraulic cylinder located in the housing of the clamping device 303. The hydraulic cylinder of the clamping device selectively presses or releases the jaws against the drill string, as illustrated by arrow 307.

[0061] The clamping devices operate in pairs to clamp the drill string onto corresponding sides of the joint, respectively. Specifically, clamping devices 302 and 303 clamp the drill string onto one side of the joint and thus provide frictional gripping of the drill string through coordinated operation to prevent rotation of the drill string relative to the jaws of the clamping devices while holding onto another drill string component to be released from one. Similarly, clamping devices 304 and 305 clamp the drill string onto the other side of the joint and thus hold onto another drill string component to be released from each other. This is in Figure 5 The diagram in the middle is schematically illustrated for Figure 1 Regarding the connector 135, clamping devices 302 and 303 clamp the drill string component 131, and clamping devices 304 and 305 clamp the drill string component 132.

[0062] Therefore, in step 202, when preparation is made to disconnect the tool, the upper disconnect tool clamping devices 302, 303 and the lower disconnect tool clamping devices 304, 305 operate to securely clamp the drill string on both sides of the joint, and thus securely clamp the two drill string components to be released from each other. This control is performed by the drilling rig control system.

[0063] In addition to clamping the drill string by means of clamping devices 302 to 305, it is also ensured that the interrupt stroke cylinder 310 is in the correct position for performing the interrupt stroke, as will be discussed below. Typically, the interrupt stroke cylinder 310 is set to the correct position before the drill string is clamped by means of clamping devices 302, 303, as will be explained below, as clamping devices 302, 303 participate in the joint release stroke (also known as, for example, the interrupt stroke).

[0064] Once the disconnecting tool, i.e., the joint loosening mechanism, is ready in step 202, the method continues to step 203, in which torque is applied by the rotating unit. According to this example, the application of torque is performed by applying pressure to the rotating unit 109. The rotating unit 109 can have various different designs and operate according to various different technologies. Figure 4 The diagram illustrates a non-restrictive example. Figure 4 The illustration shows a rotary motor 109, which can be selectively controlled to rotate in two directions of rotation as required. For example, during drilling, the rotary motor is controlled to provide rotation in the tightening direction, i.e., for tightening the threads of the various joints of the drill string by rotating the drill string. According to an embodiment of the invention, on the other hand, the rotary unit 109 is utilized for loosening the joints, in which case rotation is utilized in the opposite direction to the rotation direction during drilling. The rotation direction of the rotary motor is controlled by means of a directional control valve 401, which, according to this example, can be set to three different states 401a, 401b, and 401c, wherein state 401b disables rotation, while states 401a and 401c provide two different directions of rotation. According to this example, state 401a represents the setting of the rotary motor in the loosening direction; for this purpose, the directional control valve 401 is set to state 401a in step 204.

[0065] In addition, according to Figure 4 For example, the rotary motor 109 is controlled by a hydraulic pump 402, which allows control of the rotary unit 109 in terms of rotational pressure and rotational speed. Figure 2 In step 204, the hydraulic pump 402 is configured to control the rotating unit 109 at a relatively low rotational speed, for example, on the order of 3 RPM to 10 RPM, although various other different settings may be used. Specifically, the hydraulic pump 402 is configured to apply a low rotational speed to the rotating unit 109, such as that applied by the joint release mechanism, as will be discussed below. However, since the clamping device of the disconnect tool is already configured to clamp the drill string and thereby prevent the drill string from rotating, there will be no actual rotation of the rotating unit at this stage.

[0066] Instead, pressure will be established in the rotating unit 109, wherein the maximum pressure that can be established may, for example, depend on the current configuration of the system and is on the order of 100 to 200 bar. The pressure in the rotating circuit is monitored using a pressure sensor 403, which, according to this example, is located upstream of the directional control valve 401. However, this location is merely exemplary and may depend on, for example, the specific layout of the hydraulic circuit of the rotating unit. It is also conceivable that two or more pressure sensors could be used in this regard.

[0067] The pressure of the rotary unit is continuously built up by the hydraulic pump 402, thereby providing the release torque by means of the rotary unit, although this torque will not currently act on the joint due to the clamping of the drill string by means of the clamping device of the disconnecting tool. The pressure rise is monitored using a signal transmitted by the pressure sensor 403, and in step 205 it is determined whether the pressure of the rotary unit has reached a pressure exceeding a predetermined threshold. Unless this is the case, the method remains in step 205 for continued pressure rise. When the pressure reaches the predetermined threshold, the method proceeds to step 206. The pressure threshold in step 205 is preferably a threshold corresponding to a suitable percentage of the theoretical maximum pressure that the rotary unit can be set to. The threshold ensures that the actual pressure will be reached by being below the maximum pressure. This is because the theoretical maximum pressure may not always correspond exactly to the pressure that can actually be obtained. This threshold is, for example, on the order of 50% to 80% of the theoretical maximum pressure, but it should be understood that other limits can be used alternatively.

[0068] Therefore, when it is determined in step 205 that a predetermined pressure threshold has been reached, the method continues to step 206, in which an interrupt stroke is performed, i.e., a joint release torque is applied to the joint. This is done while maintaining pressure on the rotating unit 109. As discussed above, the disconnecting tool includes an interrupt stroke cylinder 310. The interrupt stroke cylinder 310 is hydraulically operated, and when the stroke is performed in the direction of arrow 311, the upper portion of the disconnecting tool, i.e., the portion including clamping devices 302 and 303, will rotate counterclockwise relative to the lower portion of the disconnecting tool according to the figure and according to arrow 312, and thereby counterclockwise relative to clamping devices 304, 305. The interrupt stroke cylinder 310 thus provides a joint release torque on the joint. This joint release torque can be very high and particularly significantly higher than the joint release torque that the rotating unit can transmit.

[0069] Furthermore, while the stroke of cylinder 310 is in progress, the motion performed by the interrupted stroke cylinder 310 will generate the rotational speed of the drill string component. After the interrupted stroke begins, it is determined in step 207 whether the full interrupted stroke has been completed, i.e., whether the interrupted stroke cylinder 310 has completed the stroke length and reached the end position, so that the rotation applied by the interrupted stroke has stopped. When it is determined in step 207 that the full stroke has been performed, the method continues to step 208, in which, if necessary and as described below, the gripping of the clamping devices 302, 303 is released, so that the interrupted stroke cylinder 310 can return to its initial position for subsequent interrupted strokes.

[0070] In step 209, it is determined whether a rotational pressure drop is detected during the interrupted stroke. As described above, the rotational circuit is set to a predetermined rotational speed using the hydraulic pump 402. This predetermined rotational speed is set to the rotational speed of the drill string, which is lower than the rotational speed achieved during the interrupted stroke by means of the interrupted stroke cylinder. This, in turn, means that when the interrupted stroke is executed, the flow rate provided by the hydraulic pump 402 will be insufficient to maintain the pressure in the rotational circuit, because if the drill string is released, its rotational speed will exceed the set rotational speed of the rotational unit 109.

[0071] In this scenario, during the interrupted stroke, a pressure drop will be generated in the rotary loop. The pressure signal transmitted by pressure sensor 403 is therefore monitored during the interrupted stroke, and specifically, it is determined whether a pressure drop exceeding a predetermined pressure drop is detected. This predetermined pressure drop can be, for example, some suitable pressure difference, such as a predetermined number of bar, a percentage of a pressure threshold, or determined in any other suitable manner.

[0072] The pressure drop detected during the interrupted stroke indicates that the connector has actually been loosened and the rotation of the drill string components (according to 131 in this example) has actually occurred. Therefore, the pressure drop in the rotation circuit is used as an indicator of whether the connector loosening was successful. If it is determined in step 209 that the connector loosening was successful, the method continues to step 210, in which the connector is unscrewed so that the drill string components can be separated from each other. This unscrewing can be performed in any conventional manner, for example, using the rotation unit 109. The method then continues to step 211, in which it is determined whether other connectors should be loosened, in which case the method returns to step 201. Otherwise, the method ends at step 212.

[0073] However, if no pressure drop is detected during the braking stroke, this indicates that the joint release was unsuccessful. For example, the gripping of the jaws of the clamping devices 302, 303 may not be sufficient to transmit the torque transmitted by the interrupted stroke piston. This may occur, for example, when the drill string components are covered with dust in the joint area and / or, for example, when lubrication reduces the frictional gripping of the jaws. Therefore, if it is determined in step 209 that the joint release was unsuccessful, the method continues to step 213, in which it is determined whether any other interrupted stroke attempts exist. According to an embodiment of the invention, only a limited number of interrupted strokes are allowed to attempt to release the joint before a signal indicating a failure is generated. Therefore, it is determined in step 213 whether any attempts remain, and if so, the method returns to step 202, in which the above process is repeated again.

[0074] If, in step 213, it is determined that the maximum number of attempts has been reached, for example, on the order of 2 to 7 attempts, the method continues to step 214, in which the joint loosening method is stopped and an error signal is generated to warn, for example, that the joint loosening operation by the operator and / or the drilling rig control system has not been successfully performed.

[0075] Furthermore, if, in step 210, during the unscrewing of the connector, it is determined that the rotational pressure monitored by pressure sensor 403 exceeds the pressure limit, this indicates that the connector is still not sufficiently loosened and therefore another interruption stroke should be performed. In this case, the method continues to step 213 to determine if other connector loosening attempts are available, as described above.

[0076] Therefore, according to embodiments of the present invention, a method is provided that can determine whether an interruption stroke for releasing a joint is successful. In this way, excessive interruption strokes associated with wear can be avoided, and accurate determination of the joint condition can be performed.

[0077] In addition to the above, other features can be utilized according to embodiments of the invention. As discussed, the pressure of pressure sensor 403 is monitored during the interrupted stroke, and according to embodiments of the invention, it is also determined whether a pressure drop is detected during the interrupted stroke. When this is the case, i.e., a pressure drop is detected, since the pressure drop already indicates that the joint has loosened during the partially executed interrupted stroke, it is not necessary to complete the full interrupted stroke. Therefore, according to embodiments of the invention, once a pressure drop is detected during the interrupted stroke, the interrupted stroke stops because it is not necessary to continue the interrupted stroke. This further reduces wear on components such as the grippers and drill string.

[0078] This invention can be used with virtually any type of drilling rig, wherein torque can be applied by a clamping device that grips the drill string, and wherein a rotating unit can provide torque in the direction of joint release. This invention is also applicable to underground drilling rigs and drilling rigs operating on the ground.

[0079] Furthermore, the present invention has already described the hydraulic drilling rig and the hydraulic rotary unit by way of example. However, according to the present invention, it is also conceivable that other technologies, such as an electric rotary unit including a motor, can be used. When using an electric rotary unit, for example, the current can be monitored instead of the pressure described above, and the desired rotational speed of the motor can be set directly using suitable control electronics known per se.

Claims

1. A method for determining whether a joint (134, 135, 136, 137) of a drill string (107) of a drilling rig (100) is loose, said joint (134, 135, 136, 137) connecting a first drill string assembly and a second drill string assembly (105, 106, 131, 132, 133), said drilling rig (100) comprising: A rotating unit (109) is used to rotate the drill string (107) during drilling; A device for determining an expression of the torque applied to the drill string by the rotating unit (109); The joint release mechanism (140, 300) is different from the rotating unit (109) and is configured to apply a joint release torque on the drill string (107) when the joints (134, 135, 136, 137) are released; The method includes, when the joints (134, 135, 136, 137) of the drill string (107) are loosened: A torque is applied in the joint loosening direction by means of the rotating unit (109); The joint release mechanism applies a joint release torque to the drill string; The representation of the torque applied by the rotating unit (109) is monitored during the application of the joint release torque by means of the joint release mechanism (140, 300); Whether the joints (134, 135, 136, 137) are loose is determined based on the monitored torque applied by the rotating unit (109); and When the above determination indicates that the connectors (134, 135, 136, 137) have been released, a signal indicating that the connectors (134, 135, 136, 137) have been released is generated.

2. The method according to claim 1, further comprising: The torque applied by the rotating unit (109) is monitored while the loosening torque is applied by the joint loosening mechanism (140, 300). The joints (134, 135, 136, 137) are determined to be loosened when a predetermined change in the monitored representation of the torque applied by the rotating unit (109) is detected.

3. The method according to claim 1 or 2, further comprising: The joints (134, 135, 136, 137) are determined to be loose when the monitored value of the torque applied by the rotating unit (109) drops below a predetermined threshold.

4. The method according to claim 1, further comprising: The rotation unit (109) is set to a first rotation speed, wherein the first rotation speed is lower than the rotation speed applied by the joint release mechanism (140, 300) when torque is applied to the drill string (107).

5. The method according to claim 1, further comprising: The joint release torque is applied by means of the rotating unit (109) such that the total release torque applied to the drill string (107) exceeds the torque applied by the joint release mechanism (140, 300).

6. The method of claim 1, further comprising, when the indication of the torque applied by the rotating unit (109) indicates that the joints (134, 135, 136, 137) are still tightened after a joint loosening torque is applied by the joint loosening mechanism (140, 300): The torque is repeatedly applied by the rotating unit (109) and the joint release torque is applied by means of the joint release mechanism (140, 300).

7. The method according to claim 6, further comprising: An alarm signal indicating a fault is generated when the torque applied by the rotating unit (109) and the joint loosening torque applied by means of the joint loosening mechanism (140, 300) have been repeated a predetermined number of times.

8. The method according to claim 1, further comprising: When it is determined, based on the monitoring of the torque applied by the rotating unit (109), that the joints (134, 135, 136, 137) have been loosened, the application of the joint loosening torque by means of the joint loosening mechanism (140, 300) is stopped during the application of torque by means of the joint loosening mechanism (140, 300).

9. The method according to claim 1, further comprising: Before torque is applied by the rotating unit (109), as seen from the rotating unit (109), the drill string (107) is locked at least downstream of the joints (134, 135, 136, 137) to prevent rotation.

10. The method according to claim 1, wherein the joint release mechanism (140, 300) includes a first clamping device (302, 303) and a second clamping device (304, 305), the first clamping device (302, 303) for releasably clamping the drill string on the rotating unit side of the joint (134, 135, 136, 137), and the second clamping device (304, 305) for releasably holding the drill string downstream of the joint (134, 135, 136, 137) in relation to the rotating unit (109) to prevent rotation.

11. The method according to claim 10, wherein the joint release mechanism (140, 300) further comprises a lever device (310) for applying torque to the drill string by the gripping of the first clamping device (302, 303).

12. The method of claim 11, further comprising: when monitoring of the representation of the torque applied by the rotating unit (109) indicates that the joints (134, 135, 136, 137) have loosened: Release the gripping action of the first clamping device (302, 303); and By means of the rotating unit (109), the joints (134, 135, 136, 137) are unscrewed to release the drill string components (105, 106, 131, 132, 133) connected by the joints (134, 135, 136, 137) from each other.

13. The method of claim 1, wherein the rotating unit (109) is hydraulically driven and the representation of the torque applied by the rotating unit (109) is monitored by monitoring the hydraulic pressure of the rotating unit (109), the method further comprising, before the torque is applied by the joint release mechanism (140, 300): The rotating unit (109) is set to a first rotational speed and a rotational pressure is applied to the rotating unit (109) in the unscrewing direction. Increase the rotational pressure to at least the predetermined rotational pressure.

14. The method of claim 13, further comprising: The pressure of the rotating unit (109) is monitored while the loosening torque is applied by the joint loosening mechanism (140, 300), and While the loosening torque is applied by the joint loosening mechanism (140, 300), it is determined whether the joint (134, 135, 136, 137) is loosened based on the changes in the monitored rotational pressure.

15. The method according to claim 1, further comprising: The method is performed by means of the drilling rig control system (120).

16. A non-transient computer-readable medium comprising instructions that, when executed by a computer, cause the computer to perform the method according to claim 1.

17. A system for determining whether joints (134, 135, 136, 137) of a drill string (107) of a drilling rig (100) are loose, said joints (134, 135, 136, 137) connecting a first drill string assembly and a second drill string assembly (105, 106, 131, 132, 133), said drilling rig (100) comprising: A rotating unit (109) is used to rotate the drill string (107) during drilling; A device for determining an expression of the torque applied to the drill string by the rotating unit (109); The joint release mechanism (140, 300) is different from the rotating unit (109) and is configured to apply a joint release torque acting on the drill string (107) when the joints (134, 135, 136, 137) are released; The system includes means for the following actions when the joints (134, 135, 136, 137) of the drill string (107) are loosened: A torque is applied in the joint loosening direction by means of the rotating unit (109); A joint release torque is applied to the drill string (107) by means of the joint release mechanism (140, 300); The representation of the torque applied by the rotating unit (109) is monitored during the application of the joint release torque by means of the joint release mechanism (140, 300); Whether the joints (134, 135, 136, 137) are loose is determined based on the monitored torque applied by the rotating unit (109); and When the above determination indicates that the connectors (134, 135, 136, 137) have been released, a signal indicating that the connectors (134, 135, 136, 137) have been released is generated.

18. A rock drilling rig (100) comprising the system according to claim 17.

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