Systems and methods for geophysical sensing

Abstract

A system for tracking depth of a hole drilled in a geological formation, the system comprising: one or more proximity / pressure sensors configured to track a position of an element of a drill rig; a vibration sensor configured to measure vibration from drilling by the drill rig; and a processor communicatively connected or connectable to the one or more proximity / pressure sensors and the vibration sensor and configured to track the depth of the drilled hole based on the tracked position and the measured vibration.

Description

SYSTEMS AND METHODS FOR GEOPHYSICAL SENSINGRELATED APPLICATION

[0001] The present application is related to the following patent application, the specification of which is hereby incorporated by reference in its entirety: Australian Provisional Patent Application No. 2024902974 entitled “Systems and methods for geophysical sensing”.TECHNICAL FIELD

[0002] The present disclosure generally relates to geophysical sensing systems and methods. More particularly, embodiments of the present disclosure relate to systems and methods for geophysical sensing to determine drilling depth on a drilling rig.BACKGROUND

[0003] Hole depth is a key parameter both during and after drilling of a hole in a geological formation with a drilling rig. Measurements acquired during drilling are typically indexed against time. The time at which a measurement was acquired is then correlated with the hole depth at that time to allow the measurement to be assigned to a depth. Accurate depth information is required so that measured properties of the subsurface, including but not limited to, density, strength, resistivity and natural radioactivity, are allocated to the correct strata and position in 3-dimensional space. The measurements and their geospatial location can impact commercial evaluation of resources and their extraction.

[0004] Since the hole depth and geotechnical measurements may be acquired by different systems (e.g., the depth is acquired by a rig system while the geotechnical measurements are acquired by a separate geotechnical measurement system), there can be discrepancies in time synchronization leading to complications in allocation of measurements to the correct depth. For example, if the clock in the depth measurement system is desynchronized from the clock in the geotechnical measurement system by as little as a few seconds, the geotechnicalmeasurement may be allocated to the wrong depth, making a layer of strata appear shallower or deeper, thicker or thinner than they are. This may result in miscalculation of the resource in place, thereby impacting commercial evaluation and planning.

[0005] A depth-indexed log can only be computed once the two time-indexed sources of information are brought together and time-depth conversion is performed. In the mining context, depth is generally measured by the rig system and delivered to a mine owner. The depth is generally only available to a third-party contractor if subsequently shared by the mine owner. This two-step process may slow delivery of depth logs of geotechnical measurements and therefore the ability to make timely, informed decisions about ongoing operations based on the information provided by the measurements. Delayed decisions and remedial action can result in deleterious safety and financial outcomes such as injured staff and damaged equipment due to geomechanical instability that may not be recognized in a timely manner during drilling.

[0006] It is desired to address or alleviate one or more disadvantages or limitations of the prior art, or to at least provide a useful alternative.SUMMARY

[0007] According to an aspect, there is provided a system fortracking depth of a hole drilled in a geological formation, the system comprising: one or more proximity / pressure sensors configured to track a position of an element of a drill rig; a vibration sensor configured to measure vibration from drilling by the drill rig; and a processor communicatively connected or connectable to the one or more proximity / pressure sensors and the vibration sensor and configured to track the depth of the drilled hole based on the tracked position and the measured vibration.

[0008] According to another aspect, there is provided a method of tracking depth of a hole drilled in a geological formation, the method comprising: tracking, using one or more proximity / pressure sensors, a position of an element of a drill rig; determining, using a vibration sensor, periods of drilling; and tracking, by a processor, depth of a hole drilled in the geological formation based on the tracked position and the determined periods of drilling

[0009] In an embodiment, the vibration sensor may be connected to, attached to, coupled to or mounted on to the drill rig or drill string to measure the vibration. In an embodiment, the vibration sensor may be connected to, attached to, coupled to or mounted on to the drill rig or drill string to determine the periods of drilling

[0010] The one or more proximity / pressure sensors may comprise a remote proximity / pressure sensor and a stationary proximity / pressure sensor.

[0011] The stationary proximity / pressure sensor may be connected to, attached to, coupled to or mounted on to a stationary part of the drill rig.

[0012] The remote proximity / pressure sensor may be connected to, attached to, coupled to or mounted on to a non -station ary part of the drill rig that is displaced from the stationary proximity / pressure sensor.

[0013] The one or more proximity / pressure sensors may be configured to track the position of a drill head.

[0014] The vibration sensor may be an accelerometer. In an embodiment, the vibration may be related to axial acceleration of a drilling element of the drill rig. In an embodiment, determining the periods of drilling may comprise determining axial acceleration of a drilling element of the drill rig.

[0015] In an embodiment, the measured vibration may be obtained from the vibration sensor via a radio transmitter connected to, attached to, coupled to or mounted on to the drilling element of the drill rig. In an embodiment, the determined periods of drilling from the vibration sensor may be communicated to a processor via a radio transmitter connected to, attached to, coupled to or mounted on to the drilling element of the drill rig.

[0016] The periods of drilling may be determined based on any one or both of: the measured vibration and the tracked position.

[0017] The depth of the hole may be tracked based on accumulation of net downward motion during the determined periods of drilling.

[0018] The drilling element may be subject to vibration during drilling. In various embodiments, the drilling element may be any one of: a drill head, a drill rod attached to the drill head, a drill string.

[0019] In some embodiments, a depth of a drill bit may be determined based on a length of a drilling assembly between a drill head and the drill bit. In an embodiment, a maximum depth reached by the drill bit in a hole may be tracked to be assigned as a current hole depth.

[0020] The one or more proximity sensors may be any one of: a Wi-Fi device, a radio device, a wire encoder device, a chain-drive tracking device, a linear actuator tracking device, an ultrasonic ranging device, an electromagnetic ranging device, an optical ranging device, a LiDAR ranging device, a GNSS tracking device, a GPS tracking device.

[0021] The one or more proximity / pressure sensors may be configured to track the position of a drill head by tracking a vertical height of the drill head. The vertical height may be detennined by tracking a difference in air pressure between the remote pressure sensor connected to, attached to, coupled to or mounted on to a non-stationary part of the drill rig and the stationary pressure sensor connected to, attached to, coupled to or mounted on to a stationary part of the drill rig.

[0022] In various embodiments, a position of a drill head relative to a rig drill floor may be tracked.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] One or more embodiments of the present disclosure are hereinafter described, by way of example only, with reference to the accompanying drawings in which:

[0024] Fig. 1 illustrates prior art technique of deriving depth-indexed geotechnical measurements based on time-indexed geotechnical measurements and time-indexed depth measurements;

[0025] Fig 2 shows a drilling arrangement at a drilling rig;

[0026] Fig. 3 illustrates a system for tracking depth of a hole drilled in a geological formation according to an embodiment of the present disclosure;

[0027] Fig. 4 and Fig. 4A illustrate exemplary arrangements of the system of Fig. 3 according to an embodiment of the present disclosure;

[0028] Fig. 5 is a flow chart illustrating a method of tracking depth of a hole drilled in a geological formation according to an embodiment of the present disclosure;

[0029] Fig. 6 is a flow chart illustrating a method of measuring distance between two elements of a drill rig according to an embodiment of the present disclosure;

[0030] Fig. 7 is a graph showing drill head position measured with an electromagnetic ranging device and corresponding drilled length for each drill rod for a two-rod hole;

[0031] Fig. 8 is a flowchart illustrating a method of identifying drilling intervals according to an embodiment of the present disclosure;

[0032] Fig. 9 is a pair of graphs showing acceleration vs time in the lower panel and radio signal strength indicator (RSSI) as a proxy for drill head position vs time in the upper panel measured during the drilling operation to distinguish between drilling time periods and nondrilling time periods; and

[0033] Fig. 10 is a pair of graphs showing identification of key events in the hole drilling sequence such as beginning and end of hole and number of rods used in the drill string using a combination of rig vibration data and drill head position tracking.DETAILED DESCRIPTION

[0034] Fig. 1 illustrates prior art technique 100 of deriving depth-indexed geotechnical measurements 106 based on time-indexed geotechnical measurements 102 and time-indexed depth measurements 104 (i.e., a time to depth conversion). Surface and subsurface measurements, including depth, may be recorded versus time. The common time index may then be used to merge the geotechnical measurements with the corresponding depth to derive the depth-indexed data 106. The depth-indexed geotechnical measurements may be derived and / or displayed in a tabular manner 106 and / or as a graphical representation 108 or any suitable manner.

[0035] Fig. 2 shows a drilling arrangement 200 at a drilling rig. The drilling arrangement comprises a drill head 202 to which is attached a drill rod 204 above a rig drill floor 206 through which a hole is to be drilled in a geological formation (e g., rock, soil, coal, ore). The rig drill floor 206 may be above the ground level 208. Depth is generally referenced as zero when a drill bit (not shown) attached to the bottom end of a drill string (below the drill rod shown) is located at the ground level 208 and increases with penetration into the geological formation. The drill bit position may be calculated by determining a length of the drill string and tracking a position of the drill head 202 to which the drill bit is attached via drill rods 204. The rig system generally has a wire connected to the drill head 202 that spools from a drum as the drill head moves Encoders on the drum may allow the length of spooled wire and hence the position of the drill head 202 to be measured.

[0036] Drilling may be performed by using the drill bit located at the end of a drill rod 204 (or drill pipe). The drill rod 204 may be suspended from the drill head 202 in the mast of a drill rig, as shown in Fig. 2. The geological formation (e.g., rock, soil, coal, ore) under the drill bit is broken by the application of energy transmitted through rotation and / or reciprocal motion of the drill bit when in contact with the geological formation. The fragments of the geological formation may be circulated out of the hole thereby exposing fresh geological formation to the action of the drill bit. As hole depth increases, the position of the drill head 202 may be tracked which, in conjunction with the determined length of the drill string, may permit the position of the drill bit to be determined. In various embodiments, length of the drill string may be a cumulative length of one or more components of the drill string suchas, but not limited to, drill bit, drill motor or hammer, drill sub, one or more drill rods, saver sub, drive head. The length of the drill string may be increased by adding drill rods. In various embodiments, there may only be one of each of the other components in the drill string.

[0037] Fig. 3 illustrates a system 300 for tracking depth of a hole drilled in a geological formation according to an embodiment of the present disclosure. The system 300 comprises one or more proximity / pressure sensors 302, a vibration sensor 304 and a processor 306. The one or more proximity / pressure sensors 302 may be configured to track a position of an element of a drill rig as will be described in more detail with reference to Fig. 6 below. The vibration sensor 304 may be configured to measure vibration from drilling by the drill rig. The processor 306 is communicatively connected or connectable to the one or more proximity / pressure sensors 302 and the vibration sensor 304 and may be configured to track the depth of the drilled hole based on the tracked position and the measured vibration. In an embodiment, the one or more proximity / pressure sensor(s) 302 may be connected to, attached to, coupled to or mounted on to a drill rig (not shown). In an embodiment, the vibration sensor 304 may be connected to, attached to, coupled to or mounted on to the drill rig or drill string to measure the vibration. In an embodiment, the vibration sensor 304 may be connected to, attached to, coupled to or mounted on to a drilling element (e g., the drill head, a drill rod connected to, coupled to or attached to the drill head, a drill string) associated with the drill rig to measure the vibration. It will be appreciated that any suitable wireless communication protocol (such as radio, Wi-Fi, Bluetooth, optical (laser) encoding, microwave encoding, may be used for communication between the one or more proximity / pressure sensors 302 and the processor 306, as well as between the vibration sensor 304 and the processor 306. The drilling element may be subjected to vibration during drilling by the drill rig.

[0038] Fig. 4 illustrates an exemplary arrangement of the system of Fig. 3 for determining depth of a hole drilled in a geological formation according to an embodiment of the present disclosure. The arrangement 400 comprises a stationary proximity / pressure sensor 402 and a remote proximity / pressure sensor 404. The stationary proximity / pressure sensor 402 may be connected to, attached to, coupled to or mounted on to a stationary point including part of the rig. In various embodiments, the stationary proximity / pressure sensor location isstationary such as on the ground next to the rig, or on a part of the rig which is stationary while drilling such as the drill floor, drillers cab or rig mast. The remote proximity / pressure sensor 404 may be connected to, attached to, coupled to or mounted on to a non-stationary part of the drill rig that is displaced from the stationary proximity / pressure sensor 402. In an embodiment as shown in Fig. 4, the remote proximity / pressure sensor 404 may be connected to, attached to, coupled to or mounted on to a drill head 406 or the drill string. In various embodiments, the stationary proximity / pressure sensor 402 and the remote proximity / pressure sensor 404 may be connected to, attached to, coupled to or mounted on to elements of the drill rig that are displaced from each other. In an embodiment, the remote proximity / pressure sensor 404 may be configured to communicate with the stationary proximity / pressure sensor 402. In another embodiment, the stationary proximity / pressure sensor 402 may be configured to communicate with the remote proximity / pressure sensor 404. In yet another embodiment, the stationary proximity / pressure sensor 402 and the remote proximity / pressure sensor 404 may be configured to communicate with each other.

[0039] The arrangement 400 further comprises a processor 408 (also known as an edge device). In an embodiment, the processor 408 or edge device may be installed inside a driller's cabin. The processor 408 is communicatively connectable or connected to one or both the stationary proximity / pressure sensor 402 and the remote proximity / pressure sensor 404. The processor 408 may be configured to determine position of a drill head based on the tracked position obtained from the stationary proximity / pressure sensor 402 and / or the remote proximity / pressure sensor 404. The processor 408 may be configured to determine position of a drill string (not shown) and hence position of a drill bit based on the tracked position of the drill head.

[0040] The processor 408 is further configured to track depth of the hole drilled by the rig in the geological formation based on the tracked position of the drill head and vibration measured by a vibration sensor 407 as will be described in more detail below.

[0041] The remote proximity / pressure sensor 404 may be configured to track the position of the drill head 406 by any one of Wi-Fi, radio, wire encoder, chain-drive tracking, linear actuator tracking, ultrasonic ranging, electromagnetic ranging, optical tracking, LIDAR tracking, and GNSS or GPS triangulation. The remote proximity sensor 404 and / or thestationary proximity sensor 402 may be any one of: a Wi-Fi device, a radio device, a wire encoder device, a chain-drive tracking device, a linear actuator tracking device, an ultrasonic ranging device, an electromagnetic ranging device, an optical ranging device, a LiDAR ranging device, a GNSS tracking device, a GPS tracking device.

[0042] The processor 408 may be configured to track a position of the drill head 406 by tracking a vertical height of the drill head. The vertical height of the drill head 406 may be determined based on a difference in air pressure between the remote pressure sensor 404 connected to, attached to, coupled to or mounted on to a drill string or drill head and the stationary pressure sensor 402. The stationary pressure sensor 402 may be connected to, attached to, coupled to or mounted on to a stationary point including part of the drill rig. In an embodiment, the remote pressure sensor 404 (connected to, attached to, coupled to or mounted on to the drill string) and / or the stationary pressure sensor 402 may be a digital barometric pressure sensor (e.g., TE Connectivity MS5607-02B A03) Doing so may provide vertical drill head position in a vertical mast but may be corrected for mast angle if the mast is inclined. In an embodiment, the processor 408 may be configured to track the position of the drill head relative to a rig drill floor.

[0043] A vibration sensor 407 is connected to, attached to, coupled to or mounted on to a drilling element of the drill rig (such as the drill string) that vibrates during the drilling process.Parameters of exemplary stationary proximity sensor, remote proximity sensorParameters of exemplary Processor / Edge Device

[0044] Fig. 4A. illustrates an alternative arrangement 400A of the system of Fig. 3 in which the remote proximity / pressure sensor 404 is mounted on the drill string rather than on the drill head 406 as shown in Fig.4.

[0045] It will be appreciated that while Figs. 4 and 4A show downward drilling, the present disclosure may be used for drilling holes up, horizontally etc. into a geological formation (e g., from a tunnel in an underground mine). ‘Depth’ may refer to a length of the hole regardless of the orientation of the hole.

[0046] Fig. 5 is a flow chart illustrating an exemplary method 500 of tracking depth of a hole drilled in a geological formation according to an embodiment of the present disclosure The method 500 comprises tracking, using one or more proximity / pressure sensors, a position of an element of a drill rig (step 502), determining, using a vibration sensor, periods of drilling (step 504), and tracking, by a processor, depth of a hole drilled in a geologicalformation based on the tracked position and determined periods of drilling (step 506). In an embodiment, the vibration measured by the vibration sensor may indicate when the rig is drilling. The tracked position of the element of the drill rig such as drill head position may indicate when the drill string and therefore the drill bit is moving. Position information acquired while drilling may be used to compute the depth of the drilled hole since changes in drill string position while not drilling may not increase the hole depth but may likely be related to adding or removing elements from the drill string at surface. Each of these steps will be described in more detail below. In various embodiments, an element may be any part of the drill rig that allows tracking of drilling progress such as the drill head, saver sub, or drill pipe / rod. In various embodiments, a drilling element may be an element of the drill rig that is subject to significant vibration from the drilling process such as the saver sub or drill pipe / rod. A vibration sensor mounted on a drill mast of the drill rig may not see sufficient vibration to allow drilling to be uniquely identified as shock absorbers may remove much of the vibration energy. A drill pipe may be subject to full drilling vibration, making it potentially suitable for vibrational detection of when drilling is occurring.

[0047] Fig. 6 is a flow chart illustrating an exemplary method 600 of measuring distance between two parts of a drill rig according to an embodiment of the present disclosure. One proximity sensor may be connected to, attached to, coupled to or mounted on to a stationary part of the drill rig. Another proximity sensor may be connected to, attached to, coupled to or mounted on to a non -station ary part of the drill rig. The stationary and non -station ary parts of the drill rig may be displaced from each other. In an embodiment, the pair of proximity sensors may be the stationary proximity sensor 402 and the remote proximity sensor 404 as shown in the exemplary arrangement of the system in Fig. 4). Upon receiving command to start data acquisition (step 602) (e g., through user input from a suitable input interface), the processor 306 may send a signal to one of the proximity sensors (e g , the stationary proximity sensor 402) to activate the proximity sensor to commence measurements (step 604). Upon activation, the proximity sensor measures a relative distance between itself and a second proximity sensor (e.g., the stationary proximity sensor 402 measures a relative distance between itself and the remote proximity sensor 404) (step 606). The processor 306 receives the measured relative distance from the proximity sensor (e g., the stationary proximity sensor 402) and timestamps the measured relative distance (step 608). In an embodiment, the timestamped distance data may be stored in a local database(step 610). In another embodiment, the timestamped distance may be stored in a remote database. It will be appreciated that the timestamped distance data may be stored in any suitable storage. The method 600 then proceeds to confirm if the data acquisition is to continue or be stopped at step 612. The data acquisition and distance measurement continue, i e , the method 600 may continue from step 612 to step 606 as long as the processor does not receive command to stop data acquisition and / or distance measurement (e.g., through user input from a suitable input interface). Once the processor receives a command to stop data acquisition, the method 600 proceeds from step 612 to step 614 and the data acquisition and / or distance measurement ends.

[0048] Another embodiment of the method 600 may comprise measuring air pressure difference between two parts / elements of a drill rig. One pressure sensor may be connected to, attached to, coupled to or mounted on to a stationary part of the drill rig. Another pressure sensor may be connected to, attached to, coupled to or mounted on to a non-stationary part of the drill rig. The stationary and non-stationary parts of the drill rig may be displaced from each other. In an embodiment, the pair of pressure sensors may be the stationary pressure sensor 402 and the remote pressure sensor 404 as shown in the exemplary arrangements of the system in Fig. 4, 4A). Upon receiving command to start data acquisition (e.g., through user input from a suitable input interface), the processor 306 may send a signal to one of the pressure sensors (e.g., the stationary pressure sensor 402) to activate the pressure sensor to commence measurements Upon activation, the pressure sensor measures a relative difference in air pressure between itself and a second pressure sensor (e.g., the stationary pressure sensor 402 measures a relative difference in air pressure between itself and the remote pressure sensor 404). The processor 306 receives the measured relative air pressure difference from the pressure sensor (e.g., the stationary pressure sensor 402) and timestamps the measured relative air pressure difference. In an embodiment, the timestamped air pressure difference data may be stored in a local database. In another embodiment, the timestamped air pressure difference may be stored in a remote database. It will be appreciated that the timestamped air pressure difference data may be stored in any suitable storage. The method then proceeds to confirm if the data acquisition is to continue or be stopped. The data acquisition and air pressure difference measurement continue as long as the processor does not receive command to stop data acquisition and / or air pressure difference measurement (e g., through user input from a suitable input interface). Once theprocessor receives a command to stop data acquisition, the data acquisition and / or air pressure difference measurement ends.

[0049] Fig. 7 is a graph 700 showing drill head position 702 measured with an electromagnetic ranging device (702) and corresponding drilled length for each drill rod (704) for a typical two-rod hole. Head position may be measured relative to the rig drill floor. When the drill bit is at ground level, the drill head is near the top of the mast (left) As drilling continues, the drilled length (which for the first rod may correspond to hole depth if depth has been zeroed (706) when the drill bit is at ground level) may increase while drill head elevation may decrease. When drilling the first rod's length is complete (in this example, at time around 800s), the drill head is unscrewed from the first rod and pulled up the mast so that a second rod can be attached. Drilling then continues during which the drill head elevation decreases further as it moves toward the drill floor while drilled length increases. It may be noted that drilled length may not correspond to hole depth for the second rod since the length of the first rod is to be added to determine the hole depth. In this case, the total depth of the hole at time 1130s may be about 18 m (11.4 m drilled with the first rod at 800s and 6.6 m drilled after the second rod was added). Accordingly, the depth of the drill bit may be determined by the processor based on a length of a drilling assembly between the drill head and the drill bit. The drilling assembly length may increase as more rods are added during the drilling process.

[0050] In single-pass drilling, i.e., drilling performed using a single rod or pipe, the desired depth of the hole may be less than the length of a single rod. In multi-pass drilling, additional rods may be added to the drill string to be able to drill to the desired depth. As the drill head approaches the rig drill floor, the first drill rod is clamped and the drill head unscrewed from it. The drill head is then moved to the top of the mast and another drill rod connected to it The bottom of the second rod is then screwed into the top of the first drill rod that is clamped just above the drill floor The first drill rod is unclamped, and drilling recommences using the drill string consisting of the drill bit and two rods (along with any other components such as drill subs that may be in the drill string). The addition of extra rods may be repeated as many times as necessary to achieve the desired depth of the hole.

[0051] Depth tracking in multi-pass drilling requires information of both the drill head position and the number of rods in the drill string. Acquiring this information by instrumenting the rig is often inconvenient as the rig is heavily utilized and the rig contractor may not be motivated to provide access to the rig to third parties.

[0052] Fig. 8 is a flowchart showing exemplary method 800 of identifying drilling time periods, i.e., periods of drilling, according to an embodiment of the present disclosure The method 800 comprises the steps of obtaining accelerometer time series data, which may be sampled at several kHz (step 802), obtaining rig-dependent processing parameters (step 804), processing the acceleration data based on the obtained accelerometer time series data and the obtained rig-dependent processing parameters (step 806) (e.g., data cleaning and / or de-noising before performing subsequent processing, which may include the steps of calibrating, detrending and / or smoothing acceleration), computing root mean square (RMS) of the acceleration over time windows of a few seconds (step 808), determining if RMS of acceleration is above a threshold (step 810). If the RMS of acceleration is not above the threshold, the method 800 proceeds to step 818 and it is determined that the rig is in a nondrilling time period. If at step 810, it is determined that the RMS of acceleration is above the threshold, the method 800 proceeds to determine if the rig is using a down-the-hole hammer (step 812). If the rig is not using a down-the hole hammer, the method 800 proceeds to step 816 and it is determined that the rig is in a drilling time period. If at step 812, it is determined that the rig is using a down-the hole hammer, the method 800 proceeds to determine if the hammer frequency is above a frequency threshold (step 814). If the hammer frequency is not above the frequency threshold, the method 800 proceeds to step 818 and it is determined that the rig is in a non-drilling time period. If the hammer frequency is above the frequency threshold, the method 800 proceeds to step 816 and it is determined that the rig is in a drilling time period In an embodiment, the vibration sensor may be an accelerometer, and the accelerometer time series data may be obtained from the measured vibration using the vibration sensor In an embodiment, the vibration is related to axial acceleration of the drilling element of the drill rig.

[0053] In an embodiment, the accelerometer time series data may be sampled at 5 kHz. In some embodiments, an RMS acceleration threshold of 5 g may be used to distinguish drilling from non-drilling periods. Frequency threshold may refer to the hammer strike frequency ifa pneumatic hammer is used in the drill string. Hammers may operate at above 20 Hz. In some embodiments, a frequency threshold of above 10 Hz may be used to distinguish periods when the hammer is operating (and hence drilling is taking place) from periods of no hammer operation (i.e., no drilling). In an embodiment, root mean square (RMS) of the acceleration may be computed over time windows of three seconds. Drilling may not be possible while the drill bit is above ground level. The distance between the remote proximity / pressure sensor and the drill bit when the shortest drill string is in place (normally when only the first drill rod is connected) may be drill dependent. If the remote proximity / pressure sensor is further from ground level than this distance, then the bit is above ground level. The accelerometer data may be compared to whether the drill bit is above or below ground level to identify anomalous acceleration responses such as may be experienced as the rig moves from one drill hole location to another. Accordingly, the drilling time periods may be determined based on any one or both of: the measured vibration and the tracked position.

[0054] Fig. 9 is a pair of graphs 900 showing axial acceleration vs time in the lower panel 902 and a drilling head position measurement in the upper panel 904 measured during the drilling operation. In an embodiment, the processor 306 may be further configured to determine drilling time periods based on any one or both of: the measured vibration and the determined drill head position. Vibration amplitude data (912 in the lower panel 904) may be used to distinguish drilling time periods from non-drilling time periods. A drilling head position measurement (upper panel 904), in this case radio signal strength (RSSI 906) between a drill string mounted radio transmitter and a geostationary radio receiver, may be segmented based on the rig activity. In this example, the intervals 908 may indicate nondrilling time periods while the intervals 910 may indicate drilling time periods. Drill head movement can therefore be identified during the drilling of individual rods. Rod removal events may be identified in the processing (e g., by quick and sharp dip and rise in the RSSI measurement) and marked on the plot by vertical black dashed lines. In some embodiments, an RSSI rate of change greater than 20dB / minute may indicate movement of the drill pipe faster than may be typical during drilling, indicating that the drill pipe is either being run in the hole or tripped out of the hole which may be considered as characteristic events in the drilling sequence. These mark the end of one hole and the commencement of the next, allowing the total depth of the hole to be determined by accumulating i.e., summing the increase in drilled length between the beginning- and end-of-hole events. The processor maybe configured to obtain the measured vibration from the vibration sensor via a radio transmitter connected to, attached to, coupled to or mounted on to the drill rig or the drill string. The vibration sensor may be connected to, attached to, coupled to or mounted on to the drill rig or the drill string to measure the vibration. In an embodiment, the processor 306 may be configured to obtain the measured vibration from the vibration sensor via a radio transmitter connected to, attached to, coupled to or mounted on to the drilling element of the drill rig. Tn some embodiments, the processor may be configured to determine the depth of the drilled hole based on accumulation of net downward motion during the determined drilling time periods. In some embodiments, the processor may be configured to determine the depth of the drilled hole based on the maximum depth achieved during the determined drilling time periods.

[0055] In an embodiment, the stationary proximity / pressure sensor may be mounted away from the drill rig with the remote proximity / pressure sensor mounter on the drill head or drill string. In such embodiments, the stationary proximity / pressure sensor may need to be relocated each time the rig moves from one hole location to the next. In an embodiment, the vibration sensor may also be mounted off the drill rig (e g., on the ground next to the rig) and may be relocated each time the rig moves from one hole location to the next.

[0056] Fig. 10 is a pair of graphs 1000 showing similar data as Fig. 9 with additional detail about the rod number and end of hole determination The combination of rig vibration data (1012 in the lower panel 1002) and drill head position tracking (upper panel 1004) may allow identification of key events in the hole drilling sequence such as beginning and end of hole, number of rods used in the drill string and cumulative hole depth. On the left of the upper panel 1004 on Fig. 10, a rod removal event may be identified indicating the end of the previous hole and the start of the next. A period of no change in RS SI (intervals 1010) may indicate that the drill head does not move. This may be the period during which the drill rig tractors to the next hole location, which is consistent with the relatively low amplitude accelerations observed on the lower panel 1002. Once in position, the drill head moves down until the bit is in contact with the ground at which time drilling commences (intervals 1008) and the measured axial acceleration amplitude increases significantly. Subsequent RS SI (1006) increase may indicate the drill head moving towards the drill floor, consistent with hole depth increasing.

[0057] A brief pull up of the drill head and attached drill string may be consistent with a common driller practice to clean the hole at or close to the end of drilling the full length of a rod. There may then be a brief flat period during which the top of the first rod is clamped in place, the drill head unscrewed from the first rod and lifted to the top of the drill mast The drill head may screw into the top of a second drill rod which is then positioned over the first rod and the bottom of the second rod screwed into to the top of the first rod Drilling recommences with two rods in the drill string. Once the desired hole depth is achieved, the drill head is pulled back to the top of the mast, the top of the first rod clamped in place and the bottom of the second rod unscrewed from the first rod. The top of the second rod is then unscrewed from the drill head and the second rod put aside. At this point, the drill head moves down the mast, screws into the top of the first rod then lifts the first rod such that the rod and attached bit is above ground level. This rapid down and up motion may create the characteristic signature used to identify the end of one hole and the beginning of the next in this two-rod drilling scenario. In some embodiments, a drill pipe movement speed greater than 0.5m / s may be used to distinguish rapid drill pipe motion (during running drill pipe in and out of the hole) from the slower drill pipe motion typical of drilling a geological formation (e.g., rock).

[0058] Converting head position into total hole depth comprises tracking the total number of rods in the drill string. In one embodiment, a vibration sensor (such as an accelerometer) may be connected to, attached to, coupled to or mounted on to a drilling element of the drill rig (e.g., the drill string, drill pipe or other part of a rig that vibrates during drilling). The vibration sensor may be configured and / or mounted in a manner such that it can detect drilling-related vibrations. A threshold on the amplitude of vibration may be used to identify when drilling operations are being conducted. The lower panel of Fig. 9 shows the axial acceleration measured by a drill rod-mounted accelerometer. Periods of high axial acceleration indicating active drilling can be distinguished from intervals where axial acceleration amplitude is low indicating a lack of drilling activity. The upper panel of Fig. 9 displays the radio signal strength indicator (RSSI) for a radio transmitter mounted at the top of the drill string. It will be appreciated that the radio transmitter may be used to transmit the vibration sensor data, and therefore the radio transmitter may be connected to, attached to, coupled to or mounted on to the same drilling element as the vibration sensor. RSSI increasesas the transmitter gets closer to the receiver position at the base of the drill rig mast. Like the electromagnetic ranging device results plotted in Fig. 7, this may allow the position of the drill head to be tracked. The RSSI data (upper panel 1004) has been shaded darker (1010) to indicate non-drilling periods and shaded lighter (1008) during drilling as identified from the accelerometer amplitude data (lower panel 1002). Stated differently, the processor may analyse the vibration data obtained from the vibration sensor to distinguish drilling time periods from non-drilling time periods.

[0059] In the example as shown in Fig. 9, five rods have been drilled in the one hour of operations. The beginning and end of each hole are identified to distinguish, for example, a deep hole with 5 rods from 5 shallow holes of one rod each. This may be achieved by identifying rod removal events at the end of the hole. In Fig. 9 and Fig. 10, these end of hole events are marked by vertical black dashed lines. In various embodiments, features of the drill head tracking response may be characterized according to whether they occur during the drilling time periods or the non-drilling time periods. In various embodiments, the drill head tracking response may be used to track drilled length during periods of drilling. In various embodiments, features of the drill head tracking response are used to identify the beginning and end of drilling on a hole and the number of rods used in drilling of the hole. In various embodiments, the drilled length may be accumulated over the drilling periods identified as being related to the same hole, to determine the total hole depth. In an embodiment, the processor 306 may be configured to track a maximum depth reached by a drill bit in a hole and assign that maximum depth as the current hole depth.

[0060] In single-pass drilling, this end of hole marker would not be present as only one rod is used so there is no rod removal sequence. In this case, drilled length would correspond to hole depth. In multi-pass drilling, where more than two rods are used, the number of v- shaped features, N, on the drill head tracking plot may correspond to the number of rods removed from the drill string. The total number of rods in the drill string may then be determined as N + 1. The corresponding total hole depth can then be determined as the cumulative increase in drilled length over the previous N + 1 rods.Possible Advantages

[0061] Some possible advantages of the present disclosure may include: minimal intervention of the drilling process or changes to the existing drilling instrumentation, consequent low down-time or impact on the production / operation of the rig, ability to determine drill hole depth on-site or remotely.

[0062] The present disclosure may overcome problems such as difficulties in gaining timely access to drilling depth information, so that the measurements can be presented as a depth- indexed log. Various remote head location measurements such as by using RSSI and a commercial Wi-Fi frequency radio ranging device may be suitable for measuring drill head position. The present disclosure may allow continuous position tracking of the drill head with the required centimeter-level accuracy.

[0063] During testing of the Wi-Fi ranging device, it became apparent that the depth information provided by one client was highly unreliable. The drilling interval detection logic was then devised to identify the start and stop of drilling without requiring driller input, as this was determined to be the main source of error. Once the drill / no-drill logic was sufficiently robust it became apparent that the combination of the drilling detection logic, the head position tracking and end-of-hole determination would deliver more accurate depth than provided by the client without requiring additional access to the rig beyond what was already being made available when deploying the accelerometer equipment. The present invention, by involving non-contact or wireless drill head tracking, drilling time interval identification and end-of-hole identification as discussed above, may provide a more accurate hole depth tracking system and method.

[0064] Further embodiments may involve using machine learning models that can be trained to identify additional drilling related features in the data such as reflections of signals from surfaces such as metallic surfaces and subsequent interference patterns and provide output to compensate the signals for improved head position determination and hole depth determination.Interpretation

[0065] The FIGs. included herewith show aspects of non-limiting representative embodiments in accordance with the present disclosure, and particular structural elements shown in the FIGs. may not be shown to scale or precisely to scale relative to each other. The depiction of a given element or consideration or use of a particular element number in a particular FIG. or a reference thereto in corresponding descriptive material can encompass the same, an equivalent, an analogous, categorically analogous, or similar element or element number identified in another FIG or descriptive material associated therewith The presence ofin a FIG. or text herein is understood to mean “and / or”, i.e., “X / Y” is to mean “X” or “Y” or “both X and Y”, unless otherwise indicated. The recitation of a particular numerical value or value range herein is understood to include or be a recitation of an approximate numerical value orvalue range, for instance, within + / - 20%, + / - 15%, + / - 10%, + / - 5%, + / - 2.5%, + / - 2%, + / - 1%, + / - 0.5%, or + / - 0%. The term “essentially all” or “substantially” can indicate a percentage greater than or equal to 50%, 60%, 70%, 80%, or 90%, for instance, 92.5%, 95%, 97.5%, 99%, or 100%.

[0066] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

[0067] Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0068] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

CLAIMS1. A system for tracking depth of a hole drilled in a geological formation, the system comprising: one or more proximity / pressure sensors configured to track a position of an element of a drill rig; a vibration sensor configured to measure vibration from drilling by the drill rig; and a processor communicatively connected or connectable to the one or more proximity / pressure sensors and the vibration sensor and configured to track the depth of the drilled hole based on the tracked position and the measured vibration.

2. The system of claim 1, wherein the vibration sensor is connected to, attached to, coupled to or mounted on to the drill rig or drill string to measure the vibration.

3. The system of claim 1 or 2, wherein the one or more proximity / pressure sensors comprise a remote proximity / pressure sensor and a stationary proximity / pressure sensor.

4. The system of claim 3, wherein the stationary proximity / pressure sensor is connected to, attached to, coupled to or mounted on to a stationary part of the drill rig.

5. The system of claim 3 or 4, wherein the remote proximity / pressure sensor is connected to, attached to, coupled to or mounted on to a non-stationary part of the drill rig that is displaced from the stationary proximity / pressure sensor.

6. The system of any one of claims 1 to 5, wherein the one or more proximity / pressure sensors is configured to track the position of a drill head.

7. The system of any one of claims 1 to 6, wherein the vibration sensor is an accelerometer.

8. The system of claim 7, wherein the vibration is related to axial acceleration of a drilling element of the drill rig.

9. The system of any one of claims 1 to 8, wherein the processor is configured to obtain the measured vibration from the vibration sensor via a radio transmitter connected to, attached to, coupled to or mounted on to the drilling element of the drill rig.

10. The system of any one of claims 1 to 9, wherein the processor is further configured to determine drilling time periods based on any one or both of: the measured vibration and the tracked position.

11. The system of claim 10, wherein the processor is configured to track the depth of the hole based on accumulation of net downward motion during the determined drilling time periods.

12. The system of any one of claims 8 to 11, wherein the drilling element is subject to vibration during drilling.

13. The system of any one of claims 8 to 12, wherein the drilling element is any one of: a drill head, a drill rod attached to the drill head, a drill string.

14. The system of any one of claims 1 to 13, wherein the processor is configured to determine a depth of a drill bit based on a length of a drilling assembly between a drill head and the drill bit.

15. The system of claim 14, wherein the processor is configured to track a maximum depth reached by the drill bit in a hole to be assigned as a current hole depth.

16. The system of any one of claims 1 to 15, wherein the one or more proximity sensors is any one of: a Wi-Fi device, a radio device, a wire encoder device, a chain-drive tracking device, a linear actuator tracking device, an ultrasonic ranging device, an electromagnetic ranging device, an optical ranging device, a LiDAR ranging device, a GNSS tracking device, a GPS tracking device.

17. The system of any one of claims 1 to 16, wherein the one or more proximity / pressure sensors is configured to track the position of a drill head by tracking a vertical height of the drill head.

18. The system of claim 17 when dependent on claim 2, wherein the vertical height is determined by tracking a difference in air pressure between the remote pressure sensor connected to, attached to, coupled to or mounted on to a non-stationary part of the drill rig and the stationary pressure sensor connected to, attached to, coupled to or mounted on to a stationary part of the drill rig.

19. The system of any one of claims 1 to 18, wherein the processor is configured to track a position of a drill head relative to a rig drill floor.

20. A method of tracking depth of a hole drilled in a geological formation, the method comprising: tracking, using one or more proximity / pressure sensors, a position of an element of a drill rig; determining, using a vibration sensor, periods of drilling; and tracking, by a processor, depth of a hole drilled in the geological formation based on the tracked position and the determined periods of drilling.

21. The method of claim 20, wherein the vibration sensor is connected to, attached to, coupled to or mounted on to the drill rig or drill string to determine the periods of drilling.

22. The method of claim 20 or 21, wherein the one or more proximity / pressure sensors comprise a remote proximity / pressure sensor and a stationary proximity / pressure sensor.

23. The method of claim 22, wherein the stationary proximity / pressure sensor is connected to, attached to, coupled to or mounted on to a stationary part of the drill rig.

24. The method of claim 22 or 23, wherein the remote proximity / pressure sensor is connected to, attached to, coupled to or mounted on to a non-stationary part of the drill rig that is displaced from the stationary proximity / pressure sensor.

25. The method of any one of claims 20 to 24, further comprising tracking, using the one or more proximity / pressure sensors, the position of a drill head.

26. The method of any one of claims 20 to 25, wherein the vibration sensor is an accelerometer.

27. The method of claim 26, wherein determining the periods of drilling further comprises determining axial acceleration of a drilling element of the drill rig.

28. The method of any one of claims 20 to 27, further comprising communicating the determined periods of drilling from the vibration sensor to a processor via a radio transmitter connected to, attached to, coupled to or mounted on to the drilling element of the drill rig.

29. The method of any one of claims 20 to 28, wherein determining the periods of drilling is further based on the tracked position.

30. The method of claim 29, further comprising tracking the depth of the hole based on accumulation of net downward motion during the determined periods of drilling31 . The method of any one of claims 27 to 30, wherein the drilling element is subject to vibration during drilling.

32. The method of any one of claims 27 to 31, wherein the drilling element is any one of: a drill head, a drill rod attached to the drill head, a drill string.

33. The method of any one of claims 20 to 32, further comprising determining a depth of a drill bit based on a length of a drilling assembly between a drill head and the drill bit.

34. The method of claim 33, further comprising tracking a maximum depth reached by the drill bit in a hole to be assigned as a current hole depth.

35. The method of any one of claims 20 to 34, wherein the one or more proximity sensors is any one of: a Wi-Fi device, a radio device, a wire encoder device, a chain-drive tracking device, a linear actuator tracking device, an ultrasonic ranging device, an electromagnetic ranging device, an optical ranging device, a LiDAR ranging device, a GNSS tracking device, a GPS tracking device.

36. The method of any one of claims 20 to 35, further comprising tracking the position of a drill head by tracking a vertical height of the drill head.

37. The method of claim 36 when dependent on claim 21, wherein tracking the vertical height comprises tracking a difference in air pressure between the remote pressure sensor connected to, attached to, coupled to or mounted on to a non-stationary part of the drill rig and the stationary pressure sensor connected to, attached to, coupled to or mounted on to a stationary part of the drill rig.

38. The method of any one of claims 20 to 37, further comprising tracking a position of a drill head relative to a rig drill floor.

Images