Patent Publication Number: US-2022220845-A1

Title: Rig sensor testing and calibration

Description:
TECHNICAL FIELD 
     This disclosure relates to wellbore drilling and production. 
     BACKGROUND 
     Hydrocarbons trapped in subsurface reservoirs are retrieved by first forming wellbores from the surface of the Earth to the subsurface reservoirs and then producing (that is, raising) the trapped hydrocarbons through the wellbores to the surface. Equipment used to drill the wellbores can include a drill string that is disposed in the wellbore and which includes a drill bit that drills into the Earth, and a surface rig system which supports the drill string and provides other functions. The surface rig system can include multiple surface components such as equipment to hoist and rotate the drill string and to pump drilling fluid into the drill string. 
     SUMMARY 
     This disclosure describes a system, tool, and method for monitoring the accuracy of the various rig sensors positioned on the various surface components of a well drilling system. 
     Certain aspects of the subject matter herein can be implemented as a method including attaching a sensor calibration tool to a drill string. The sensor calibration tool includes a first tool sensor configured to measure a first operational parameter. A first tool sensor measurement of the first operational parameter is received from the first tool sensor, where the drill string is disposed at least partially within a wellbore and supported by a surface rig system and the sensor calibration tool is positioned on the drill string at a surface location proximate to the surface rig system. A first rig sensor measurement of the first operational parameter is received from a first rig sensor positioned on a first surface component of the surface rig system. The first rig sensor is calibrated based on a comparison of the first tool sensor measurement with the first rig sensor measurement. 
     An aspect combinable with any of the other aspects can include the following features. The first tool sensor measurement and the first rig sensor measurement each include a respective plurality of measurements of the first operational parameter over a period of time. 
     An aspect combinable with any of the other aspects can include the following features. The sensor calibration tool includes a memory module. The first rig sensor measurement is stored in the memory module. 
     An aspect combinable with any of the other aspects can include the following features. The receiving of the first tool sensor measurement and the receiving of the first rig sensor measurement are by a data gathering and analysis module comprising a computer system comprising one or more processors and a non-transitory computer readable medium storing instructions executable by the one or more processors to perform operations. 
     An aspect combinable with any of the other aspects can include the following features. The sensor calibration tool includes a wireless transmitter. The first tool sensor measurement is transmitted from the sensor calibration tool via wireless telemetry to the data gathering and analysis module. 
     An aspect combinable with any of the other aspects can include the following features. A difference between the first tool sensor measurement and the first rig sensor measurement is calculated by the data gathering and analysis module. The difference is compared to a stored difference threshold by the data gathering and analysis module. An alert is transmitted by the data gathering and analysis module in response to the difference exceeding the stored difference threshold. 
     An aspect combinable with any of the other aspects can include the following features. Historical measurements from the first rig sensor of the first operational parameter are stored by the data gathering and analysis module. The historical measurements are adjusted by the data gathering and analysis module based in part on the comparison of the first tool sensor measurement with the first rig sensor measurement. 
     An aspect combinable with any of the other aspects can include the following features. The first operational parameter can include a frequency of rotation of the drill string, a pressure of fluid pumped through a stand pipe line and down the drill string, a flow rate of fluid pumped through the stand pipe line and down the drill string, a temperature of fluid pumped through the stand pipe line and down the drill string, a torque load of the drill string, a frequency of mud pump strokes, a weight of the drill string, vibrations in the drill string, or acoustic signals in proximity of the drill string. 
     An aspect combinable with any of the other aspects can include the following features. The first surface component of the surface rig system includes a stand pipe line, a top drive, a mud pump, a mud pit, a rotary table, or a draw works for a drill line. 
     An aspect combinable with any of the other aspects can include the following features. The first rig sensor is included in a plurality of rig sensors, each rig sensor positioned on a respective one of a plurality of surface components of the surface rig system, each rig sensor configured to measure a respective one of a plurality of operational parameters. The first tool sensor is included in a tool sensor bank disposed on the sensor calibration tool, the tool sensor bank comprising a plurality of tool sensors, each tool sensor of the tool sensor bank configured to measure a respective one of the plurality of operational parameters. A respective tool sensor measurement of the respective operational parameter for which the tool sensor is configured to measure receiving is received from each tool sensor in the tool sensor bank. A respective rig sensor measurement of the respective operational parameter for which the surface rig sensor is configured to measure is received from each of a plurality of rig sensors. Each of the plurality of rig sensors is calibrated based on a comparison of the respective tool sensor measurement with the respective tool sensor measurement of the respective operational parameter for which the rig sensor is configured to measure. 
     Certain aspects of the subject matter herein can be implemented as a drilling sensor calibration system. The drilling sensor calibration system includes a surface rig system configured to support a drill string, a first rig sensor positioned on a first surface component of the surface rig system, the first rig sensor configured to measure a first operational parameter, and a sensor calibration tool configured to be attached to the drill string at a surface location proximate to the surface rig system, the sensor calibration tool comprising a first tool sensor configured to measure the first operational parameter. The drilling sensor calibration system also includes a data gathering and analysis module includes a computer system comprising one or more processors and a non-transitory computer readable medium storing instructions executable by the one or more processors to perform operations. The operations include receiving, from the first tool sensor, the first tool sensor measurement of the first operational parameter, receiving, from the first rig sensor, the first rig sensor measurement of the first operational parameter, and displaying a comparison of the first tool sensor measurement with the first rig sensor measurement. 
     An aspect combinable with any of the other aspects can include the following features. The operations include calibrating the first rig sensor based on a comparison of the first tool sensor measurement with the first rig sensor measurement 
     An aspect combinable with any of the other aspects can include the following features. The first tool sensor measurement includes a plurality of measurements over a period of time. 
     An aspect combinable with any of the other aspects can include the following features. The sensor calibration tool includes a memory module. The first rig sensor measurement is stored in the memory module. 
     An aspect combinable with any of the other aspects can include the following features. The sensor calibration tool includes a wireless transmitter. The first tool sensor measurement is transmitted via wireless telemetry from the sensor calibration tool to the data gathering and analysis module. 
     An aspect combinable with any of the other aspects can include the following features. The operations include calculating, by the data gathering and analysis module, a difference between the first tool sensor measurement and the first rig sensor measurement, comparing, by the data gathering and analysis module, the difference to a stored difference threshold, and transmitting, by the data gathering and analysis module, an alert in response to the difference exceeding the stored difference threshold. 
     An aspect combinable with any of the other aspects can include the following features. The operations include storing, by the data gathering and analysis module, historical measurements from the first rig sensor of the first operational parameter, and adjusting, by the data gathering and analysis module, the historical measurements based in part on the comparison of the first tool sensor measurement with the first rig sensor measurement. 
     An aspect combinable with any of the other aspects can include the following features. The first operational parameter includes a frequency of rotation of the drill string, a pressure of fluid pumped through a stand pipe line and down the drill string, a flow rate of fluid pumped through the stand pipe line and down the drill string, a temperature of fluid pumped through the stand pipe line and down the drill string, a torque load of the drill string, a frequency of mud pump strokes, a weight of the drill string, vibrations in the drill string, or acoustic signals in proximity of the drill string. 
     An aspect combinable with any of the other aspects can include the following features. The first surface component of the surface rig system includes a stand pipe line, a top drive, a mud pump, a mud pit, a rotary table, or a draw works for a drill line. 
     An aspect combinable with any of the other aspects can include the following features. The first rig sensor is included in a plurality of rig sensors, each rig sensor positioned on a respective one of a plurality of surface components of the surface rig system. Each rig sensor is configured to measure a respective one of a plurality of operational parameters, and wherein the first tool sensor is included in a tool sensor bank disposed on the sensor calibration tool, the tool sensor bank comprising a plurality of tool sensors, each tool sensor of the tool sensor bank configured to measure a respective one of the plurality of operational parameters. The operations include receiving, from each tool sensor in the tool sensor bank, a respective sensor measurement of the respective operational parameter for which the tool sensor is configured to measure, receiving, from each of a plurality of rig sensors, a respective sensor measurement of the respective operational parameter for which the rig sensor is configured to measure, and displaying a comparison of the respective tool sensor measurement with the respective tool sensor measurement of the respective operational parameter for which the rig sensor is configured to measure. 
     The details of one or more implementations of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a drawing of an example well system in accordance with an embodiment of the present disclosure. 
         FIG. 2  is a drawing of a sensor calibration tool in accordance with an embodiment of the present disclosure. 
         FIG. 3  is a drawing of a sensor bank on a sensor calibration tool in accordance with an embodiment of the present disclosure. 
         FIGS. 4A and 4B  are drawings of a sensor calibration tool in accordance with an alternative embodiment of the present disclosure. 
         FIG. 5  is a process flow diagram of a method for determining an accuracy of a rig sensor in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     During drilling operations, it can be useful for an operator to have information regarding various operational parameters of the well drilling system such as drill string weight, revolutions-per-minute (RPM) of the drill string, drilling fluid pressure, drilling fluid flow, drilling fluid temperature, drill string vibrations, noise, and/or tension, compression, drag, and/or strain of the drill string. Such information can be used by the operator to monitor drilling operations so as to optimize rate of penetration and otherwise maximize the safe, efficient, and cost-effective operation of the well system. 
     Sensors that measure such operational parameters are typically positioned on various surface components of the rig system. The kind, location, and accuracy of rig sensors can vary greatly with different well systems in different locations and different kinds and types of equipment and sensors. In addition, it is common for rig sensors to go out of calibration or otherwise develop inaccuracies that are reflected in the operational parameter information received by the operator. Different skill levels of crew members can also contribute to differences in operational parameter information received by the operator from the rig sensors. 
     This disclosure describes a system, tool, and method for monitoring the accuracy of the various rig sensors positioned on the various surface components of a well drilling system. In accordance with an embodiment of the disclosure, an instrumented sub comprising a sensor calibration tool housing one or multiple tool sensors can be attached to the drill string. Each of the tool sensors on the sensor calibration tool can measure an operational parameter that is also measured by a corresponding rig sensor that is positioned on a surface component. Sensor data from the rig sensors and the tool sensors can be captured by a data gathering and analysis module and displayed for the operator on a display screen. The system can be configured to alert the operator if differences between the rig sensor measurement and the tool sensor measurement exceed a threshold value. Based on the sensor data and comparison information provided by the system, rig sensors can be calibrated and/or otherwise adjusted and managed to enhance sensor data accuracy. 
     Properly calibrated and accurate rig sensors can contribute to a higher rate-of-penetration and avoid drill string failure and/or other conditions or events that can result in lost time and increased costs. The sensor calibration tool can be easily attached or detached from the drill string and carried to a different wellsite, such that the system with the same tool sensor suite can be utilized at multiple drilling locations, thus minimizing time and costs and allowing for consistent sensor calibration procedures and results. 
     In accordance with an embodiment of the present disclosure, the sensor calibration tool and system can be brought to a wellsite in response to an incident such as stuck pipe or twist off and installed on the well system to determine whether and the extent to which any rig sensors are out-of-calibration or otherwise inaccurate. Historical data related to the incident can be analyzed and corrected if necessary utilizing data from the sensor calibration tool. Data from the sensor calibration tool can be utilized in preventative tools such as machine learning algorithms for automated operations or rig crew training. 
       FIG. 1  illustrates a well system  100  in accordance with one embodiment of the present disclosure. In the illustrated embodiment, Well system  100  includes a conventional rotary land rig. However, the present disclosure is applicable to other types of onshore or offshore drilling rigs (including top drive, power swivel, down hole motor, and coiled tubing units) and to other drilling and/or production rigs or platforms that are operable to bore through the earth and/or produce hydrocarbons or other resources from the earth. 
     Well system  100  includes a surface rig system  102  and a drill string  150 . Surface rig system  102  includes several surface components at or near the surface, including a derrick  104  that is supported above a rig floor  106 . In other embodiments, a mast may be used in lieu of a derrick  104 . Surface rig system  102  further includes a lifting gear that includes a crown block  108  mounted to the derrick  104 , a travelling block  110 , a hook  116 , and a swivel  118 . The crown block  108  and the travelling block  110  are interconnected by a cable  112  that is driven by draw works  114  to control the upward and downward movement of the travelling block  110 . Travelling block  110  carries hook  116  from which is suspended swivel  118 . The swivel  118  supports a top drive  138 , which is also a surface component of surface rig system  102 . Other surface components of surface rig system  102  include slips  122 , mud pumps  124 , stand pipe line  132 , and mud tanks  128 , described in more detail below. In other embodiments, surface rig system  102  can include other, more, and/or fewer surface components. 
     Drill string  150  includes drill pipe  154  (which comprises a plurality of interconnected drill pipe sections), and further includes a saver sub  152  at the top (uphole) end of drill string  150  and a bottom-hole assembly (BHA)  156  at the downhole end of drill string  150 . BHA  156  includes a drill bit  158  and a mud motor  160 , and may also include stabilizers, drill collars, measurement well drilling (MWD) instruments, and the like. 
     Drill string  150  is positioned at least partially in well bore  101 . The top of drill string  150 , specifically, saver sub  152 , is attached to top drive  138 . In this way, surface rig system  102  supports drill string  150 . The weight of drill string  150  may be further supported by slips  122 . 
     Surface rig system  102  also pumps drilling fluid, or mud,  126 , down drill string  150 . More specifically, mud pumps  124  draw drilling fluid  126  from mud tanks  128  through stand pipe line  132 . The drilling fluid  126  is delivered to the drill string  150  through stand pipe line  132  which connects to swivel  118 . From the swivel  118 , the drilling fluid  126  travels through the drill string  150  to the BHA  156 , where it turns the mud motor  160  and exits the bit  158  to scour the formation and lift the resultant cuttings through the annulus to the surface. At the surface, mud tanks  128  receive the drilling fluid  126  from the well bore  101  through a flow line  134 . The mud tanks  128  and/or flow line  134  can include a shaker or other device to remove the cuttings. 
     Drilling is accomplished by rotating the drill string  150 , which in turn rotates the bit  158 , and applying weight on bit  158 . Surface rig system  102 , and specifically, top drive  138 , provides the rotation to drill string  150  within bore hole  101 . Alternatively or in addition, a down hole motor may rotate the bit  158  independently of the drill string  150  and the top drive  138 . As previously described, the cuttings produced as bit  158  drills into the earth are carried out of bore hole  101  by the drilling fluid  126  supplied by pumps  124 . 
     In some embodiments, a drilling rig may include a rotary table at the rig floor instead of a top drive. In such embodiments, the rotary table is part of the surface rig system and provides the rotation to drill string  150  during drilling operations. 
     Information regarding operational parameters of well system  100  such as drill string weight, revolutions-per-minute (RPM) of the drill string, drilling fluid pressure, drilling fluid flow, drilling fluid temperature, drill string vibrations, noise, and/or tension, compression, drag, and/or strain of the drill string can come from rig sensors positioned on (that is, attached to or positioned on the surface of or within) some of the surface components of surface rig system  102 , such as draw works  114 , stand pipe line  132 , mud pumps  124 , and/or top drive  138 . 
     For example, in some embodiments, a hook load rig sensor  170  can attached to draw works  114  to measure the weight supported by draw works  114 . Hook load rig sensor  170  can be attached at or near the “dead end” of cable  112  or another suitable location. 
     In some embodiments, additional rig sensors that measure other operational parameters are positioned on other surface components of surface rig system  102 . For example, fluid pressure rig sensor  172  can be disposed on or within stand pipe line  132  to measure a pressure of drilling fluid  126  fluid pumped through a stand pipe line  132  and down drill string  150 . A flow rig sensor  174  can be disposed one or within mud pumps  124  to measure the rate of flow of drilling fluid  126  pumped by mud pumps  124  through stand pipe line  132  and down drill string  150 . In some embodiments, flow rig sensor  174  can detect the number of strokes per minute of mud pumps  124  instead of or in addition to the flow rate. A temperature rig sensor  176  can be disposed on or within mud pumps  124  to measure a temperature of drilling fluid  126 . 
     In some embodiments, one or more sensors can be attached to top drive  138 . For example, a torque rig sensor  178  can be attached to top drive  138  to measure a torque load of the drill string. A revolutions-per-minute (RPM) rig sensor  180  can be attached to top drive  138  to measure a frequency of rotation of the drill string. A vibration rig sensor  182  can be attached to top drive  138  to measure vibration at or near the top of drill string  150 . An acoustic rig sensor  184  can be attached to top drive  138  to measure noise or other acoustic signals at or near the top of drill string  150 . 
     In drilling systems where a rotary table is used instead of a top drive, the torque, RPM, vibration, and acoustic rig sensors can be attached to or near the rotary table instead of top drive  138 . Vibration and/or acoustic rig sensors can also be attached to other surface components of surface rig system  102 . 
     In some embodiments, all of the above-described rig sensors are attached to the surface components of surface rig system  102  as described above. In other embodiments, only one or some of the above-described rig sensors are attached to the surface rig system  102  components. In some embodiments, additional or other rig sensors can be included to measure the above-described or other operational parameters, and/or rig sensors can be placed within, on, or near different or additional surface components of surface rig system  102  than the ones described above. 
     In an embodiment of the present disclosure, a sensor calibration tool  162  can be attached to drill string  150 . As described in more detail in reference to  FIGS. 2 and 3 , sensor calibration tool  162  can house a tool sensor bank which can include one or more tool sensors which can measure operational parameters such as drill string weight, torque, revolutions-per-minute (RPM) of the drill string, drilling fluid pressure, drilling fluid flow, drilling fluid temperature, drill string vibrations, noise, tension, compression, drag, and/or pipe bending. Sensor calibration tool  162  can be attached to drill string  150  before insertion of drill string  150  into wellbore  101  or after at least a portion of drill string  150  is disposed at least partially within wellbore  101 . As described in further detail below, data from the tool sensors on sensor calibration tool  162  can be compared to data from the rig sensors on the surface components of surface rig system  102 , the accuracy of the rig sensors can be analyzed and sensors calibrated or otherwise adjusted as necessary so as to optimize drilling operations. 
     As described in more detail in  FIGS. 2-4 , sensor calibration tool  162  can include, in addition to a sensor bank including one or multiple tool sensors, a communication module to transmit the tool sensor data. The communication module which can include a wireless transmitter (such as wi-fi, Bluetooth, laser, or acoustic) or other suitable data transmission means. In some embodiments, sensor calibration tool  162  can also include a memory module to store historical or current sensor data from the tool sensors. Sensor calibration tool  162  can also include a power module to provide power to the tool sensors and/or the communication module and/or memory module. 
     Well system  100  also includes a data gathering and analysis module  190  to receive and/or analyze sensor data from the rig sensor or sensors and the tool sensor or sensors, as described in further detail below. Data gathering and analysis module  190  can include a wireless reader or other receiver to download information from sensor calibration tool  162  such as sensor data from tool sensors of sensor calibration tool  162 . Data gathering and analysis module  190  can also be configured to receive data from one, some, or all of the rig sensors of surface rig system  102 , via wired or wireless connection. 
     In some embodiments, data gathering and analysis module  190  includes a computer system that comprises one or more processors, and a computer-readable medium (for example, a non-transitory computer-readable medium) storing computer instructions executable by the one or more processors to perform operations. In some embodiments, data gathering and analysis module  190  is configured to receive display sensor data received from the rig sensors and/or the tool sensors and transmit the information to data display screen  192 , which can provide the information to an operation using a graphical user interface (GUI) or other suitable user interface. Sensor data from a rig sensor of a surface component of surface rig system  102  can be displayed next to sensor data from a tool sensor on sensor calibration tool  162  for the same operational parameter. An operator observing a difference in the sensor data between the rig sensor and the corresponding tool sensor can take a suitable action such as calibrating or otherwise adjusting the rig sensor and/or replacing a failed rig sensor. 
     For example, sensor calibration tool  162  can include a weight sensor which provides information regarding the weight of drill string  150 . Measurements from the weight tool sensor can be displayed next to data from hook load rig sensor  170  on draw works  114 . Sensor calibration tool  162  can also include a tool sensor that is an RPM sensor to measure the RPM of drill string  150 , and measurements from this RPM tool sensor can be displayed next to data from RPM rig sensor  180  on top drive  138 . Values from other tool sensors on sensor calibration tool  162  can likewise be displayed next to corresponding values for the same operational parameter from rig sensors on surface rig system  102 . 
     In some embodiments, while attached to drill string  150 , sensor calibration tool  162  is positioned at a surface location proximate to surface rig system  102  and the tool sensor measurements and rig sensor measurements can be transmitted and received while the tool is positioned at this surface location. In some embodiments, sensor calibration tool  162  is positioned above rig floor  106 . In some embodiments, sensor calibration tool  162  can be positioned at a near-surface location some distance downhole, for example, within about 300 feet of the surface. For example, in the embodiment illustrated in  FIG. 1 , sensor calibration tool  162  is positioned on the drill string just above rig floor  106  and is proximate to surface components of surface rig system  102  such as top drive  138 , draw works  114 , and mud pumps  124 . Such a surface position allows for data from sensor calibration tool to be most easily, quickly, and accurately transmitted to data gathering and analysis module  190  and/or otherwise accessed via wireless transmission or other means. Also, so positioned at a surface location, data from the tool sensors on sensor calibration tool  162  can in some embodiments be more accurately and directly compared to the data from the nearby rig sensors of surface rig system  102 , for a given operational parameter. In some embodiments, locating sensor calibration tool  162  at a surface location can result in more accurate torque measurements, as no frictional losses from rubbing of the tool against the wellbore would be required to be taken into account. In some embodiments, sensor calibration tool  162  can be positioned at a surface location and drill pipes  154  added to drill string  150  below sensor calibration tool  162 , and so positioned can provide measurements of the weight of individual drill pipes  154  as they are added to the drill string. 
     As drilling continues and drill string  150  travels further downhole, sensor calibration tool  162  can be removed from drill string  150  before sensor calibration tool  162  descends into (or further into) wellbore  101 . In some embodiments, sensor calibration tool  162  can then be reattached at a higher point on drill string  150  to maintain the position of sensor calibration tool  162  at a surface location as drilling operations continue. In some embodiments, sensor calibration tool  162  is attached to saver sub  152  and drill pipes  154  added beneath sensor calibration tool  162 , such that sensor calibration tool  162  remains at a surface location as drill pipes  154  and other portions of drill string  150  are lowered into wellbore  101 . In some embodiments, sensor calibration tool  162  is lowered into wellbore  101  along with other components of drill string  150  as drill string  150  travels further downhole. 
     As described in further detail with regards to  FIGS. 2 and 4 , sensor calibration tool  162  can be configured as a threaded sub or a clamp that can be readily and easily attached and/or detached from drill string  150 . In this way, sensor calibration tool  162  can continue to be positioned at a surface location. Also, because it is easily attachable and detachable, sensor calibration tool  162  can be easily deployed at different well sites, thus minimizing time and costs and allowing for consistent sensor results and consistent calibration procedures and results for different well systems. Likewise, in some embodiments, data gathering and analysis module  190  and display screen  192  can be portable units. In some embodiments, some of the gathering and analysis functions of data gathering and analysis module  190  can be performed in a cloud or edge network. 
     In some embodiments, data gathering and analysis module  190  can adjust the measurements from the rig sensors and/or the tool sensors so as to make the measurements more directly comparable. For example, in some embodiments, a measurement from hook load rig sensor  170  on draw works  114  can be adjusted by removing (manually or automatically) the known weight of travelling block  110 , hook  116 , swivel  118 , and top drive  138  such that what is left represents the weight of drill string  150  and can be more directly compared to the measurement of the weight of drill string  150  from the weight sensor on sensor calibration tool  162 . In some embodiments, no adjustment is necessary because any adjustment would be within the margin of error of the sensor. 
     In some embodiments, sensor data can be streamed and displayed in real time, and can include single measurements and/or multiple measurements over time. In some embodiments, historical sensor data can be downloaded from sensor calibration tool  162  to data gathering and analysis module  190  and retrieved by the operator from data gathering and analysis module  190  as needed by inputting retrieval commands. 
     In some embodiments, data gathering and analysis module  190  can be configured to analyze the sensor data and provide alerts the operator when a calibration is required and/or perform other actions. For example, data gathering and analysis module  190  can be configured to calculate the difference between a measurement from a tool sensor on sensor calibration tool  162  of an operational parameter and the corresponding rig sensor measurement (from a rig sensor on a surface component of surface rig system  102 ) of that operational parameter. Some difference may be an acceptable operational variation, but a greater difference may be an unacceptable variation indicating an out-of-calibration sensor or other condition requiring action by the operator. In some embodiments, data gathering and analysis module  190  can store a threshold value of the difference, above which above which calibration or another action is required. A difference below the threshold value would not trigger an alert; a difference above the threshold value would trigger an alert. 
     In some embodiments, once the alert is received, the operator can calibrate the rig sensor as necessary in light of the data from the sensor calibration tool  162 . Such calibration can be done manually or automatically. 
     In some embodiments, data gathering and analysis module  190  can be configured to measure and record the standard deviation between tool sensor data and rig sensor data. In some embodiments, data gathering and analysis module  190  can be configured to store historical data including values from the rig sensors and the tool sensors and/or standard deviation data. In some embodiments, data gathering and analysis module  190  can be configured to compare historical data from rig sensors with historical data from tool sensors of their respective operational parameters. In some embodiments, data gathering and analysis module  190  can adjust or correct historical rig sensor data based on this comparison with historical or current tool sensor data and provide the operator with an output comprising such adjusted or corrected historical sensor rig data. 
     In some embodiments, sensor data from sensor calibration tool  162  can be used to train machine learning algorithms and/or otherwise used to understand and optimize drill string behavior and/or drilling optimization. 
     In some embodiments, the sensor calibration tool and system can be brought to a wellsite in response to an incident such as stuck pipe or twist off and installed on the well system to determine whether and the extent to which any rig sensors are out-of-calibration or otherwise inaccurate. Where similar incidents have occurred at multiple wells, the system and method can be brought to each of those wells such that historical data related to the incidents at the different wells can be analyzed, corrected, and compared using a common tool and system. By correcting historical data and comparing corrections from different rig systems (which may have significant discrepancies in rig sensor accuracy) with the same calibration tool, a better understanding of the incident(s) can be achieved and future incidents avoided. Data from the system and method can be utilized in preventative tools such as machine learning algorithms for automated operations or rig crew training. 
       FIG. 2  is a drawing of sensor calibration tool  162  in accordance with an embodiment of the present disclosure. In the embodiment shown in  FIG. 2 , sensor calibration tool  162  is an instrumented sub including a mandrel  202 , an upper connection  204 , and a lower connection  206 . Upper connection  204  and lower connection  206  can comprise threaded connections that can be attached to threaded drill pipe segments of drill string  150  using known methods. For example, in one embodiment, sensor calibration tool  162  can be attached to drill pipe segment or segments that are in a mouse hole at the rig, and the drill pipe and tool combination then attached to drill string  150 . In another embodiment, sensor calibration tool  162  can be threaded directly to a drill pipe that is already attached to drill string  150 . 
     Sensor calibration tool  162  as shown in  FIG. 2  also includes a sensor bank  210  that includes multiple individual tool sensors to measure operational parameters, as described above. Sensor bank  210  is described in further detail in  FIG. 3 . Sensor calibration tool  162  also includes power source  212  which can include one or more batteries. In some embodiments, power can be provided from another source (for example, a power cable and/or a fluid turbine) in lieu of or in addition to batteries. Communication module  214  can include a wireless transmitter (such as wi-fi, Bluetooth, laser, or acoustic) or other suitable means for transmitting sensor data. Sensor calibration tool  162  can further include a memory module (not shown). In some embodiments, the memory module can comprise a SDD or HDD or similar memory system and a USB interface. 
       FIG. 3  is a drawing of a sensor bank on a sensor calibration tool  162  in accordance with an embodiment of the present disclosure. The features of sensor bank the sensor bank illustrated in  FIG. 3  are described in reference to the elements described in reference to  FIGS. 1 and 2 . 
     In the illustrated embodiment, the sensor bank illustrated in  FIG. 3  is sensor bank  210  of  FIG. 2  and is disposed on mandrel  202 . In the illustrated embodiment, sensor bank  210  includes eight tool sensors: weight tool sensor  310 , fluid pressure tool sensor  312 , flow tool sensor  314 , temperature tool sensor  316 , torque tool sensor  318 , RPM tool sensor  320 , vibration tool sensor  322 , acoustic tool sensor  324 . Each tool sensor can measure a respective operational parameter. In some embodiments, sensor bank  210  may include a different number (for example, fewer) tool sensors and/or sensors for different and/or additional operational parameters than as described above. Sensor data from the tool sensors can be compared to rig sensor data for the corresponding operational parameter, as described above in reference to  FIG. 1 . 
     Specifically, for example, weight tool sensor  310  can measure the weight of drill string  150 , and data from weight tool sensor  310  can be compared to data from hook load rig sensor  170 . Fluid pressure tool sensor  312  can measure the pressure of drilling fluid flowing through drill string  150 , and data from fluid pressure tool sensor  312  can be compared to data from fluid pressure rig sensor  172 . Flow tool sensor  314  can measure the flow rate of drilling fluid flowing through drill string  150  and data from flow tool sensor  314  can be compared to data from flow rig sensor  174 . Temperature tool sensor  316  can measure the temperature of drilling fluid flowing through drill string  150 , and data from temperature tool sensor  316  can be compared to data from temperature rig sensor  176 . Torque tool sensor  318  can measure a torque load of drill string  150 , and data from torque tool sensor  318  can be compared to data from torque rig sensor  178 . RPM tool sensor  320  can measure the frequency of rotation of drill string  150 , and data from RPM tool sensor  320  can be compared to data from RPM rig sensor  180 . Vibration tool sensor  322  can measure vibrations of drill string  150 , and data from vibration tool sensor  322  can be compared to data from vibration rig sensor  182 . Acoustic tool sensor  324  can measure noise or other acoustic signals at or near the top of drill string  150 , and data from acoustic tool sensor  324  can be compared to data from acoustic rig sensor  184 . 
       FIGS. 4A and 4B  are drawings of a sensor calibration tool in accordance with an alternative embodiment of the present disclosure. In the embodiment shown in  FIG. 4 , the sensor calibration tool is configured as a clamp that can be attached to the exterior of drill string  150 . 
     Referring to  FIG. 4A , sensor calibration clamp tool  400  includes a body  402  that splits in half. In  FIG. 4A , sensor calibration clamp tool  400  is in an open position revealing interior surface  403 . Interior surface  403  includes latching mechanisms  404  which are configured to attach to an exterior surface of a drill string (such as drill string  150  of  FIG. 1 ), as shown in  FIG. 4B . 
     Like sensor calibration tool  162  of  FIG. 2 , sensor calibration clamp tool  400  includes a sensor bank  210 , a power source  212 , and a communication module  214 . Sensor bank  210 , power source  212 , and communication module  214  have a structure and function as described in reference to  FIG. 3 . 
     Sensor calibration clamp tool  400  can, in some embodiments, be more easily attachable and detachable from the drill string than sensor calibration tool  162 , resulting in further cost and time savings. In some embodiments, sensor bank  210  of sensor calibration clamp tool  400  may have the same suite of tool sensors as sensor calibration tool  162 . In some embodiments, sensor bank  210  of calibration clamp tool  400  may have a different suite and/or a different number of tool sensors than the sensor bank of sensor calibration tool  162 . For example, in some embodiments, sensor calibration clamp tool  400  can include tool sensors for torque, RPM, and vibration, but not include sensors for flow, pressure, and/or temperature. 
       FIG. 5  is a process flow diagram of a method for determining an accuracy of a rig sensor in accordance with an embodiment of the present disclosure. The method is described with reference to the components described in reference to  FIGS. 1-2 . 
     Referring to  FIG. 5 , method  500  begins at block  502  with attaching a sensor calibration tool (such as sensor calibration tool  162 ) to a drill string (such as drill string  150 ). As described in reference to  FIGS. 1 and 2 , the sensor calibration tool includes on or many tool sensors, each of which is configured to measure a respective operational parameter. 
     As described in reference to  FIG. 1 , the drill string can be disposed at least partially within a wellbore and supported by a surface rig system and the sensor calibration tool can be positioned on the drill string at a surface location proximate to the surface rig system. Proceeding to block  504 , a receiver such as a data gathering and analysis module  190  receives a tool sensor measurement of the respective operational parameter from one of the tool sensors. 
     Proceeding to block  506 , the data gathering and analysis module or other suitable receiver receives a rig sensor measurement from a rig sensor positioned on a surface component of the surface rig system, of the same operational parameter that was also measured by the tool sensor operational parameter 
     Proceeding to block  508 , a difference between the rig sensor measurement and the tool sensor measurement is determined. This can be done manually by an operator or automatically by the data gathering and analysis module. 
     In some embodiments, the difference can be compared to a difference threshold. If the difference threshold is exceeded, the data gathering and analysis module can transmit an alert to the operator. 
     Proceeding to block  510 , the rig sensor is calibrated based on the comparison of the tool sensor measurement with the rig sensor measurement. Calibration can be done manually or automatically as described in reference to  FIG. 1 . 
     In this disclosure, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed in this disclosure, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section. 
     In this disclosure, “approximately” or “substantially” means a deviation or allowance of up to 10 percent (%) and any variation from a mentioned value is within the tolerance limits of any machinery used to manufacture the part. Likewise, “about” can also allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range. 
     Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “0.1% to about 5%” or “0.1% to 5%” should be interpreted to include about 0.1% to about 5%, as well as the individual values (for example, 1%, 2%, 3%, and 4%) and the sub-ranges (for example, 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “X, Y, or Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise. 
     While this disclosure contains many specific implementation details, these should not be construed as limitations on the subject matter or on what may be claimed, but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in this disclosure in the context of separate implementations can also be implemented, in combination, in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations, separately, or in any suitable sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     Particular implementations of the subject matter have been described. Nevertheless, it will be understood that various modifications, substitutions, and alterations may be made. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results. Accordingly, the previously described example implementations do not define or constrain this disclosure.