Abstract:
Embodiments of the present invention generally relate to methods and apparatus for improving top drive operations. In one embodiment a method of ensuring safe operation of a top drive includes operating a top drive, thereby exerting torque on a first tubular to makeup or breakout a first threaded connection between the first tubular and a second tubular. The method further includes monitoring for break-out of a second connection between a quill of the top drive and the first tubular; and stopping operation of the top drive and/or notifying an operator of the top drive if break-out of the second connection is detected.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Prov. Pat. App. No. 60/866,322 (Atty. Dock. No. WEAT/0749L), entitled “Top Drive Backout Interlock Method”, filed on Nov. 17, 2006, which is herein incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the present invention generally relate to methods and apparatus for improving top drive operations. 
         [0004]    2. Description of the Related Art 
         [0005]    It is known in the industry to use top drive systems to rotate a drill string to form a borehole. Top drive systems are equipped with a motor to provide torque for rotating the drilling string. The quill of the top drive is typically threadedly connected to an upper end of the drill pipe in order to transmit torque to the drill pipe. Top drives may also be used in a drilling with casing operation to rotate the casing. 
         [0006]    To drill with casing, most existing top drives use a threaded crossover adapter to connect to the casing. This is because the quill of the top drives is typically not sized to connect with the threads of the casing. The crossover adapter is design to alleviate this problem. Generally, one end of the crossover adapter is designed to connect with the quill, while the other end is designed to connect with the casing. In this respect, the top drive may be adapted to retain a casing using a threaded connection. 
         [0007]    However, the process of connecting and disconnecting a casing using a threaded connection is time consuming. For example, each time a new casing is added, the casing string must be disconnected from the crossover adapter. Thereafter, the crossover must be threaded to the new casing before the casing string may be run. Furthermore, the threading process also increases the likelihood of damage to the threads, thereby increasing the potential for downtime. 
         [0008]    As an alternative to the threaded connection, top drives may be equipped with tubular gripping heads to facilitate the exchange of wellbore tubulars such as casing or drill pipe. Generally, tubular gripping heads have an adapter for connection to the quill of top drive and gripping members for gripping the wellbore tubular. Tubular gripping heads include an external gripping device such as a torque head or an internal gripping device such as a spear. An exemplary torque head is described in U.S. Patent Application Publication No. 2005/0257933, filed by Pietras on May 20, 2004, which is herein incorporated by reference in its entirety. An exemplary spear is described in U.S. Patent Application Publication Number US 2005/0269105, filed by Pietras on May 13, 2005, which is herein incorporated by reference in its entirety. 
         [0009]    In most cases, the adapter of the tubular gripping head connects to the quill of the top drive using a threaded connection. The adapter may be connected to the quill either directly or indirectly, e.g., through another component such as a sacrificial saver sub. One problem that may occur with the threaded connection is inadvertent breakout of that connection during operation. For example, in a drilling with casing operation, a casing connection may be required to be backed out (i.e., unthreaded) either during the pulling of a casing string or to correct an unacceptable makeup. It may be possible that the left hand torque required to break out the casing connection exceeds the breakout torque of the connection between the adapter and the quill, thereby inadvertently disconnecting the adapter from the quill and creating a hazardous situation on the rig. 
         [0010]    There is a need, therefore, for methods and apparatus for ensuring safe operation of a top drive. 
       SUMMARY OF THE INVENTION 
       [0011]    Embodiments of the present invention generally relate to methods and apparatus for improving top drive operations. In one embodiment a method of ensuring safe operation of a top drive includes operating a top drive, thereby exerting torque on a first tubular to makeup or breakout a first threaded connection between the first tubular and a second tubular. The method further includes monitoring for break-out of a second connection between a quill of the top drive and the first tubular; and stopping operation of the top drive and/or notifying an operator of the top drive if break-out of the second connection is detected. 
         [0012]    In another embodiment, a method of ensuring safe operation of a top drive includes operating a top drive, thereby rotating a quill of the top drive. The quill of the top drive is connected to a torque head or a spear. Hydraulic communication between the torque head or spear and a hydraulic pump is provided by a swivel. A bearing is disposed between a housing and a shaft of the swivel. The method further includes determining acceptability of operation of the bearing by monitoring a torque exerted on the swivel housing by the bearing; and stopping operation of the top drive and/or notifying an operator of the top drive if the bearing operation is unacceptable. 
         [0013]    In another embodiment, a torque head or spear for use with a top drive includes a body having an end for forming a connection with a quill of the top drive; a gripping mechanism operably connected to the body for longitudinally and rotationally gripping a tubular; and a computer configured to perform an operation. The operation includes monitoring for break-out of the connection; and stopping operation of the top drive and/or notifying an operator of the top drive if break-out of the connection is detected. 
         [0014]    In another embodiment, a torque head or spear for use with a top drive includes a body having an end for forming a connection with a quill of the top drive; a gripping mechanism operably connected to the body for longitudinally and rotationally gripping a tubular; and a swivel. The swivel includes a housing; a shaft disposed in the housing and connected to the body; a bearing disposed between the shaft and the housing; and a strain gage disposed on the housing and operable to indicate torque exerted on the housing by the bearing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0016]      FIG. 1  is a partial view of a rig having a top drive system. 
           [0017]      FIG. 2  is an isometric view of a torque sub usable with the top drive system.  FIG. 2A  is a side view of a torque shaft of the torque sub.  FIG. 2B  is an end view of the torque shaft with a partial sectional view cut along line  2 B- 2 B of  FIG. 2A .  FIG. 2C  is a cross section of  FIG. 2A .  FIG. 2D  is an isometric view of the torque shaft.  FIG. 2E  is an electrical diagram showing data and electrical communication between the torque shaft and a housing of the torque sub. 
           [0018]      FIG. 3  is a block diagram illustrating a tubular make-up system, according to one embodiment of the present invention. 
           [0019]      FIG. 4  is a side view of a top drive system employing a torque meter.  FIG. 4A  is an enlargement of a portion of  FIG. 4 .  FIG. 4B  is an enlargement of another portion of  FIG. 4 . 
           [0020]      FIG. 5  is a flow chart illustrating operation of an interlock of the make-up system of  FIG. 3 , according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  shows a drilling rig  10  applicable to drilling with casing operations or a wellbore operation that involves picking up/laying down tubulars. The drilling rig  10  is located above a formation at a surface of a well. The drilling rig  10  includes a rig floor  20  and a v-door  800 . The rig floor  20  has a hole  55  therethrough, the center of which is termed the well center. A spider  60  is disposed around or within the hole  55  to grippingly engage the casings  30 ,  65  at various stages of the drilling operation. As used herein, each casing  30 ,  65  may include a single casing or a casing string having more than one casing. Furthermore, aspects of the present invention are equally applicable to other types of wellbore tubulars, such as drill pipe. 
         [0022]    The drilling rig  10  includes a traveling block  35  suspended by cables  75  above the rig floor  20 . The traveling block  35  holds the top drive  50  above the rig floor  20  and may be caused to move the top drive  50  longitudinally. The top drive  50  may be supported by the travelling block  35  using a swivel which allows injection of drilling fluid into the top drive  50 . The top drive  50  includes a motor  80  which is used to rotate the casing  30 ,  65  at various stages of the operation, such as during drilling with casing or while making up or breaking out a connection between the casings  30 ,  65 . A railing system (partially shown) is coupled to the top drive  50  to guide the longitudinal movement of the top drive  50  and to prevent the top drive  50  from rotational movement during rotation of the casings  30 ,  65 . 
         [0023]    Disposed below the top drive  50  is a tubular gripping member such as a torque head  40 . The torque head  40  may be utilized to grip an upper portion of the casing  30  and impart torque from the top drive to the casing  30 . The torque head  40  may be coupled to an elevator  70  using one or more bails  85  to facilitate the movement of the casing  30  above the rig floor  20 . In another embodiment, the bails  85  may be coupled to the top drive  50  or components attached thereto. Additionally, the rig  10  may include a pipe handling arm  100  to assist in aligning the tubulars  30 ,  65  for connection. In must be noted that other tubular gripping members such as a spear are contemplated for use with the top drive. An exemplary torque head suitable for use with a top drive  50  is disclosed in U.S. Patent Application Publication No. 2005/0257933, filed by Pietras on May 20, 2004, which is herein incorporated by reference in its entirety. An exemplary spear is described in U.S. Patent Application Publication Number US 2005/0269105, filed by Pietras on May 13, 2005, which is herein incorporated by reference in its entirety. 
         [0024]    Torque Sub 
         [0025]      FIG. 2  shows an exemplary torque sub/swivel  600 . The torque sub  600  may be connected to the top drive  50  for measuring a torque applied by the top drive  50 . The torque sub  600  may be disposed between the top drive  50  and the torque head  40 . The swivel  600  may provide hydraulic communication between stationary hydraulic lines and the torque head  40  for operation thereof. The torque sub/swivel  600  may include a swivel housing  605 , a swivel shaft  612 , a torque shaft  610 , an interface  615 , and a controller  620 . The swivel housing  605  is a tubular member having a bore therethrough. Longitudinally and rotationally coupled to the housing  605  is a bracket  605   a  for coupling the swivel housing  605  to the railing system, thereby preventing rotation of the swivel housing  605  during rotation of the top drive  50 , but allowing for vertical movement of the swivel housing  605  with the top drive  50  under the traveling block  35 . The interface  615  and the controller  620  are both mounted on the swivel housing  605 . The controller  620  and the torque shaft  610  may be made from metal, such as stainless steel. The interface  615  may be made from a polymer. The bails  85  may also be pivoted to the swivel housing  605 . The torque shaft  610  and the swivel shaft  612  are disposed in the bore of the swivel housing  605 . The swivel shaft  612  is disposed between the torque shaft  610  and the swivel housing  605  and rotationally coupled to the torque shaft  610   a . The swivel housing  605  is supported from the swivel shaft  612  by one or more swivel bearings (not shown) to allow rotation of the swivel shaft  612  relative to the swivel housing  605 . 
         [0026]      FIG. 2A  is a side view of the torque shaft  610  of the torque sub  600 .  FIG. 2B  is an end view of the torque shaft  610  with a partial sectional view cut along line  2 B- 2 B of  FIG. 2A .  FIG. 2C  is a cross section of  FIG. 2A .  FIG. 2D  is an isometric view of the torque shaft  610 . The torque shaft  610  is a tubular member having a flow bore therethrough. The torque shaft  610  includes a threaded box  610   a , a groove  610   b , one or more longitudinal slots  610   c  (preferably two), a reduced diameter portion  610   d , and a threaded pin  610   e , a metal sleeve  610   f , and a polymer (preferably rubber, more preferably silicon rubber) shield  610   g.    
         [0027]    The threaded box  610   a  receives the quill of the top drive  50 , thereby forming a rotational connection therewith. Other equipment, such as a thread saver sub or a thread compensator (not shown), may be connected between the torque sub/swivel  600  and the quill. The pin  610   e  is received by a connector of the torque head  40 , thereby forming a rotational connection therewith. A failsafe, such as set screws, may be added to the toque sub  610 /torque head  40  connection. The groove  610   b  receives a secondary coil  630   b  (see  FIG. 2E ) which is wrapped therearound. Disposed on an outer surface of the reduced diameter portion  610   d  are one or more strain gages  680 . Each strain gage  680  may be made of a thin foil grid and bonded to the tapered portion  610   d  of the shaft  610  by a polymer support, such as an epoxy glue. The foil strain gauges  680  are made from metal, such as platinum, tungsten/nickel, or chromium. Four strain gages  680  may be arranged in a Wheatstone bridge configuration. The strain gages  680  are disposed on the reduced diameter portion  610   d  at a sufficient distance from either taper so that stress/strain transition effects at the tapers are fully dissipated. The slots  610   c  provide a path for wiring between the secondary coil  630   b  and the strain gages  680  and also house an antenna  645   a  (see  FIG. 2E ). 
         [0028]    The shield  610   g  is disposed proximate to the outer surface of the reduced diameter portion  610   d . The shield  610   g  may be applied as a coating or thick film over strain gages  680 . Disposed between the shield  610   g  and the sleeve  610   f  are electronic components  635 , 640  (see  FIG. 2E ). The electronic components  635 , 640  are encased in a polymer mold  630  (see  FIG. 2E ). The shield  610   g  absorbs any forces that the mold  630  may otherwise exert on the strain gages  680  due to the hardening of the mold. The shield  610   g  also protects the delicate strain gages  680  from any chemicals present at the wellsite that may otherwise be inadvertently splattered on the strain gages  680 . The sleeve  610   f  is disposed along the reduced diameter portion  610   d . A recess is formed in each of the tapers to seat the shield  610   f . The sleeve  610   f  forms a substantially continuous outside diameter of the torque shaft  610  through the reduced diameter portion  610   d . Preferably, the sleeve  610   f  is made from sheet metal and welded to the shaft  610 . The sleeve  610   f  also has an injection port formed therethrough (not shown) for filling fluid mold material to encase the electronic components  635 , 640 . 
         [0029]      FIG. 2E  is an electrical diagram showing data and electrical communication between the torque shaft  610  and the enclosure  605 . A power source  660  may be provided in the form of a battery pack in the controller  620 , an-onsite generator, utility lines, or other suitable power source. The power source  660  is electrically coupled to a sine wave generator  650 . Preferably, the sine wave generator  650  will output a sine wave signal having a frequency less than nine kHz to avoid electromagnetic interference. The sine wave generator  650  is in electrical communication with a primary coil  630   a  of an electrical power coupling  630 . 
         [0030]    The electrical power coupling  630  is an inductive energy transfer device. Even though the coupling  630  transfers energy between the stationary interface  615  and the rotatable torque shaft  610 , the coupling  630  is devoid of any mechanical contact between the interface  615  and the torque shaft  610 . In general, the coupling  630  acts similar to a common transformer in that it employs electromagnetic induction to transfer electrical energy from one circuit, via its primary coil  630   a , to another, via its secondary coil  630   b , and does so without direct connection between circuits. The coupling  630  includes the secondary coil  630   b  mounted on the rotatable torque shaft  610 . The primary  630   a  and secondary  630   b  coils are structurally decoupled from each other. 
         [0031]    The primary coil  630   a  may be encased in a polymer  627   a , such as epoxy. The secondary coil  630   b  may be wrapped around a coil housing  627   b  disposed in the groove  610   b . The coil housing  627   b  is made from a polymer and may be assembled from two halves to facilitate insertion around the groove  610   b . Optionally, the secondary coil  630   b  is then molded in the coil housing  627   b  with a polymer. The primary  630   a  and secondary coils  630   b  are made from an electrically conductive material, such as copper, copper alloy, aluminum, or aluminum alloy. The primary  630   a  and/or secondary  630   b  coils may be jacketed with an insulating polymer. In operation, the alternating current (AC) signal generated by sine wave generator  650  is applied to the primary coil  630   a . When the AC flows through the primary coil  630   a , the resulting magnetic flux induces an AC signal across the secondary coil  630   b . The induced voltage causes a current to flow to rectifier and direct current (DC) voltage regulator (DCRR)  635 . A constant power is transmitted to the DCRR  635 , even when torque shaft  610  is rotated by the top drive  100 . The primary coil  630   a  and the secondary coil  630   b  have their parameters (i.e., number of wrapped wires) selected so that an appropriate voltage may be generated by the sine wave generator  650  and applied to the primary coil  630   a  to develop an output signal across the secondary coil  630   b.    
         [0032]    The DCRR  635  converts the induced AC signal from the secondary coil  630   b  into a suitable DC signal for use by the other electrical components of the torque shaft  610 . In one embodiment, the DCRR outputs a first signal to the strain gages  680  and a second signal to an amplifier and microprocessor controller (AMC)  640 . The first signal is split into sub-signals which flow across the strain gages  680 , are then amplified by the amplifier  640 , and are fed to the controller  640 . The controller  640  converts the analog signals from the strain gages  680  into digital signals, multiplexes them into a data stream, and outputs the data stream to a modem associated with controller  640  (preferably a radio frequency modem). The modem modulates the data stream for transmission from antenna  645   a . The antenna  645   a  transmits the encoded data stream to an antenna  645   b  disposed in the interface  615 . The antenna  645   b  sends the received data stream to a modem, which demodulates the data signal and outputs it to a joint analyzer controller  655 . Alternatively, the analog signals from the strain gages may be multiplexed and modulated without conversion to digital format. Alternatively, conventional slip rings, an electric swivel coupling, roll rings, or transmitters using fluid metal may be used to transfer data from the shaft  610  to the interface  615 . 
         [0033]    The torque shaft may further include a turns counter  665 ,  670 . The turns counter may include a turns gear  665  and a proximity sensor  670 . The turns gear  665  is rotationally coupled to the torque shaft  610 . The proximity sensor  670  is disposed in the interface  615  for sensing movement of the gear  665 . The sensitivity of the gear/sensor  665 , 670  arrangement may be, for example, one-tenth of a turn; one-hundredth of a turn; or one-thousandth of a turn. However, other sensitivities are contemplated. The sensor  670  is adapted to send an output signal to the joint analyzer controller  655 . It is contemplated that a friction wheel/encoder device (see  FIG. 4 ), a gear and pinion arrangement, or other suitable gear/sensor arrangements known to person of ordinary skill in the art may be used to measure turns of the torque shaft. 
         [0034]    The controller  655  is adapted to process the data from the strain gages  680  and the proximity sensor  670  to calculate respective torque, longitudinal load, and turns values therefrom. For example, the controller  655  may de-code the data stream from the strain gages  680 , combine that data stream with the turns data, and re-format the data into a usable input (i.e., analog, field bus, or Ethernet) for a make-up computer system  706  (see  FIG. 3 ). Using the calculated values, the controller may control operation of the top drive  50  and/or the torque head  40 . The controller  655  may be powered by the power source  660 . The controller  655  may also be connected to a wide area network (WAN) (preferably, the Internet) so that office engineers/technicians may remotely communicate with the controller  655 . Further, a personal digital assistant (PDA) may be connected to the WAN so that engineers/technicians may communicate with the controller  655  from any worldwide location. 
         [0035]    The torque sub  600  is also disclosed in U.S. Patent App. Pub. No. 2007/0251701 filed by Jahn, et al. on Apr. 27, 2007, which application is herein incorporated by reference in its entirety. 
         [0036]    Tubular Makeup System 
         [0037]      FIG. 3  is a block diagram illustrating a tubular make-up system  700 , according to one embodiment of the present invention. The tubular make-up system  700  may include the top drive  50 , torque head  40 , a computer system  706  and torque sub  600 , torque meter  900 , or upper turns counter  905   a  (without lower turns counter  905   b ). Whether the tubular make-up system  700  includes the torque sub  600 , torque meter  900 , or the torque head turns counter may depend on factors, such as rig space and cost. During make-up of a tubing assembly  30 ,  65 , a computer  716  of the computer system  706  monitors the turns count signals and torque signals  714  from the torque sub  600  and compares the measured values of these signals with predetermined values. If the torque sub  600  or torque meter  900  is not used, the computer  716  may calculate torque and rotation output of the top drive  50  by measuring voltage, current, and/or frequency (if AC top drive) of the power  713  input to the top drive. For example, in a DC top drive, the speed is proportional to the voltage input and the torque is proportional to the current input. Due to internal losses of the top drive, the calculation is less accurate than measurements from the torque sub  600 ; however, the computer  716  may compensate the calculation using predetermined performance data of the top drive  50  or generalized top drive data or the uncompensated calculation may suffice. An analogous calculation may also be made for a hydraulic top drive (i.e., pressure and flow rate). 
         [0038]    Predetermined values may be input to the computer  716  via one or more input devices  718 , such as a keypad. Illustrative predetermined values which may be input, by an operator or otherwise, include a delta torque value  724 , a delta turns value  726 , minimum and maximum turns values  728  and minimum and maximum torque values  730 . During makeup of a tubing assembly, various output may be observed by an operator on output device, such as a display screen, which may be one of a plurality of output devices  720 . The format and content of the displayed output may vary in different embodiments. By way of example, an operator may observe the various predefined values which have been input for a particular tubing connection. Further, the operator may observe graphical information such as a representation of the torque rate curve  500  and the torque rate differential curve  500   a . The plurality of output devices  720  may also include a printer such as a strip chart recorder or a digital printer, or a plotter, such as an x-y plotter, to provide a hard copy output. The plurality of output devices  720  may further include a horn or other audio equipment to alert the operator of significant events occurring during make-up, such as the shoulder condition, the terminal connection position and/or a bad connection. 
         [0039]    Upon the occurrence of a predefined event(s), the computer system  706  may output a dump signal  722  to automatically shut down the top drive unit  100 . For example, dump signal  722  may be issued upon the terminal connection position and/or a bad connection. The comparison of measured turn count values and torque values with respect to predetermined values is performed by one or more functional units of the computer  716 . The functional units may generally be implemented as hardware, software or a combination thereof. By way of illustration of a particular embodiment, the functional units are software. In one embodiment, the functional units include a torque-turns plotter algorithm  732 , a process monitor  734 , a torque rate differential calculator  736 , a smoothing algorithm  738 , a sampler  740 , a comparator  742 , a deflection compensator  752 , and an interlock  749 . It should be understood, however, that although described separately, the functions of one or more functional units may in fact be performed by a single unit, and that separate units are shown and described herein for purposes of clarity and illustration. As such, the functional units  732 - 742 ,  749 , and  752  may be considered logical representations, rather than well-defined and individually distinguishable components of software or hardware. 
         [0040]    The frequency with which torque and rotation are measured may be specified by the sampler  740 . The sampler  740  may be configurable, so that an operator may input a desired sampling frequency. The measured torque and rotation values may be stored as a paired set in a buffer area of computer memory. Further, the rate of change of torque with rotation (i.e., a derivative) may be calculated for each paired set of measurements by the torque rate differential calculator  736 . At least two measurements are needed before a rate of change calculation can be made. In one embodiment, the smoothing algorithm  738  operates to smooth the derivative curve (e.g., by way of a running average). These three values (torque, rotation, and rate of change of torque) may then be plotted by the plotter  732  for display on the output device  720 . 
         [0041]    In one embodiment, the rotation value may be corrected to account for system deflections using the deflection compensator  752 . As discussed above, torque is applied to a tubular  30  (e.g., casing) using a top drive  50 . The top drive  50  may experience deflection which is inherently added to the rotation value provided by the turns gear  665  or other turn counting device. Further, a top drive unit  50  will generally apply the torque from the end of the tubular that is distal from the end that is being made. Because the length of the tubular may range from about 20 ft. to about 90 ft., deflection of the tubular may occur and will also be inherently added to the rotation value provided by the turns gear  665 . For the sake of simplicity, these two deflections will collectively be referred to as system deflection. In some instances, the system deflection may cause an incorrect reading of the tubular makeup process, which could result in a damaged connection. 
         [0042]    To compensate for the system deflection, the deflection compensator  752  utilizes a measured torque value to reference a predefined value (or formula) to find (or calculate) the system deflection for the measured torque value. The deflection compensator  652  includes a database of predefined values or a formula derived therefrom for various torque and system deflections. These values (or formula) may be calculated theoretically or measured empirically. Empirical measurement may be accomplished by substituting a rigid member, e.g., a blank tubular, for the tubular and causing the top drive unit  50  to exert a range of torque corresponding to a range that would be exerted on the tubular to properly make-up a connection. The torque and rotation values measured would then be monitored and recorded in a database. The deflection of the tubular may also be added into the system deflection. 
         [0043]    Alternatively, instead of using a blank for testing the top drive, the end of the tubular distal from the top drive unit  50  may simply be locked into a spider. The top drive unit  50  may then be operated across the desired torque range while the resulting torque and rotation values are measured and recorded. The measured rotation value is the rotational deflection of both the top drive unit  50  and the tubular. Alternatively, the deflection compensator  752  may only include a formula or database of torques and deflections for the tubular. The theoretical formula for deflection of the tubular may be pre-programmed into the deflection compensator  752  for a separate calculation of the deflection of the tubular. Theoretical formulas for this deflection may be readily available to a person of ordinary skill in the art. The calculated torsional deflection may then be added to the top drive deflection to calculate the system deflection. 
         [0044]    After the system deflection value is determined from the measured torque value, the deflection compensator  752  then subtracts the system deflection value from the measured rotation value to calculate a corrected rotation value. The three measured values—torque, rotation, and rate of change of torque—are then compared by the comparator  742 , either continuously or at selected rotational positions, with predetermined values. For example, the predetermined values may be minimum and maximum torque values and minimum and maximum turn values. 
         [0045]    Based on the comparison of measured/calculated/corrected values with predefined values, the process monitor  734  determines the occurrence of various events and whether to continue rotation or abort the makeup. In one embodiment, the process monitor  734  includes a thread engagement detection algorithm  744 , a seal detection algorithm  746  and a shoulder detection algorithm  748 . The thread engagement detection algorithm  744  monitors for thread engagement of the two threaded members. Upon detection of thread engagement a first marker is stored. The marker may be quantified, for example, by time, rotation, torque, a derivative of torque or time, or a combination of any such quantifications. During continued rotation, the seal detection algorithm  746  monitors for the seal condition. This may be accomplished by comparing the calculated derivative (rate of change of torque) with a predetermined threshold seal condition value. A second marker indicating the seal condition is stored when the seal condition is detected. 
         [0046]    At this point, the turns value and torque value at the seal condition may be evaluated by the connection evaluator  750 . For example, a determination may be made as to whether the corrected turns value and/or torque value are within specified limits. The specified limits may be predetermined, or based off of a value measured during makeup. If the connection evaluator  750  determines a bad connection, rotation may be terminated. Otherwise rotation continues and the shoulder detection algorithm  748  monitors for shoulder condition. This may be accomplished by comparing the calculated derivative (rate of change of torque) with a predetermined threshold shoulder condition value. When the shoulder condition is detected, a third marker indicating the shoulder condition is stored. The connection evaluator  750  may then determine whether the turns value and torque value at the shoulder condition are acceptable. 
         [0047]    In one embodiment, the connection evaluator  750  determines whether the change in torque and rotation between these second and third markers are within a predetermined acceptable range. If the values, or the change in values, are not acceptable, the connection evaluator  750  indicates a bad connection. If, however, the values/change are/is acceptable, the target calculator  752  calculates a target torque value and/or target turns value. The target value is calculated by adding a predetermined delta value (torque or turns) to a measured reference value(s). The measured reference value may be the measured torque value or turns value corresponding to the detected shoulder condition. In one embodiment, a target torque value and a target turns value are calculated based off of the measured torque value and turns value, respectively, corresponding to the detected shoulder condition. 
         [0048]    Upon continuing rotation, the target detector  754  monitors for the calculated target value(s). Once the target value is reached, rotation is terminated. In the event both a target torque value and a target turns value are used for a given makeup, rotation may continue upon reaching the first target or until reaching the second target, so long as both values (torque and turns) stay within an acceptable range. Alternatively, the deflection compensator  752  may not be activated until after the shoulder condition has been detected. 
         [0049]    Whether a target value is based on torque, turns or a combination, the target values are not predefined, i.e., known in advance of determining that the shoulder condition has been reached. In contrast, the delta torque and delta turns values, which are added to the corresponding torque/turn value as measured when the shoulder condition is reached, are predetermined. In one embodiment, these predetermined values are empirically derived based on the geometry and characteristics of material (e.g., strength) of two threaded members being threaded together. Exemplary embodiments of the tubular makeup system are disclosed in U.S. Provisional Patent Application Ser. No. 60/763,306, filed on Jan. 30, 2006, which application is herein incorporated by reference in its entirety. 
         [0050]    Torque Meter 
         [0051]      FIG. 4  is a side view of a top drive system employing the torque meter  900 .  FIG. 4A  is an enlargement of a portion of  FIG. 4 .  FIG. 4B  is an enlargement of another portion of  FIG. 4 . The torque meter  900  includes upper  905   a  and lower  905   b  turns counters. The upper turns counter  905   a  is located on the torque head  40 . Alternatively, if a crossover or direct connection between the tubular and the quill  910  is used instead of the torque head, then the upper turns counter  905   a  may be located below the connection therebetween. Alternatively, the upper turns counter  905   a  may be located near an upper longitudinal end of the first tubular  30 . The lower turns counter  915   b  is located along the first tubular  30  proximate to the box  65   b . Each turns counter includes a friction wheel  920 , an encoder  915 , and a bracket  925   a,b . The friction wheel  920  of the upper turns counter  905   a  is held into contact with the torque head  40 . The friction wheel  920  of the lower turns counter  905   b  is held into contact with the first tubular  30 . Each friction wheel is coated with a material, such as a polymer, exhibiting a high coefficient of friction with metal. The frictional contact couples each friction wheel with the rotational movement of outer surfaces of the drive shaft  910  and first tubular  30 , respectively. Each encoder  915  measures the rotation of the respective friction wheel  920  and translates the rotation to an analog signal indicative thereof. Alternatively, a gear and proximity sensor arrangement or a gear and pinion arrangement may be used instead of a friction wheel for the upper  905   a  and/or lower  905   b  turns counters. In this alternate, for the lower turns counter  905   b , the gear would be split to facilitate mounting on the first tubular  402 . 
         [0052]    These rotational values may be transmitted to the joint make-up system  700  for analysis. Due to the arrangement of the upper  905   a  and lower  905   b  turns counters, a torsional deflection of the first tubular  402  may be measured. This is found by subtracting the turns measured by the lower turns counter  905   b  from the turns measured by the upper turns counter  905   a . By turns measurement, it is meant that the rotational value from each turns counter  905   a,b  has been converted to a rotational value of the first tubular  402 . Once the torsional deflection is known a controller or computer  706  may calculate the torque exerted on the first tubular by the top drive  100  from geometry and material properties of the first tubular. If a length of the tubular  402  varies, the length may be measured and input manually (i.e. using a rope scale) or electronically using a position signal from the draw works  105 . The turns signal used for monitoring the make-up process would be that from the bottom turns counter  905   b , since the measurement would not be skewed by torsional deflection of the first tubular  402 . 
         [0053]    Interlock Operation 
         [0054]      FIG. 5  is a flow chart illustrating operation of the interlock  749 , according to another embodiment of the present invention. As discussed above, there is a threaded connection between the torque head  40 /torque sub  600  (if present) and the quill and may also be one or more intermediate connections (hereinafter top drive connections). The interlock  749  may detect a breakout at one of these connections. Typically, the connections are right-hand connections as are most tubulars that the top drive is used to make up. However, to break-out connections, left-hand torque is applied to the tubular  30  which also tends to break-out the top drive connections. Additionally, the interlock  749  may be used to detect break-out of the top drive connections during make-up of left-hand connections, such as expandable tubulars, or any time the top-drive  50  exerts an opposite-hand torque to that of the top-drive connections. Use of the interlock  749  is not limited to top drives equipped with torque heads or spears but may also be used with crossovers or direct connection between the top drive and the tubular. 
         [0055]    At step  5 - 1 , the interlock  749  monitors the output torque of the top drive  50  and compares the output torque to a predetermined or programmed output torque. As discussed above, this act may be performed using the torque sub  600 , torque meter  900 , or calculated from input power  713 . A left-hand direction of the output torque may be indicated by a negative torque value. Examples of the predetermined torque are any left-hand torque and a maximum (minimum if positive convention) breakout torque of the top drive connections. If the monitored torque is less than (assuming negative convention for left hand torque) the predetermined torque, the interlock proceeds to step  5 - 2  of the control logic. 
         [0056]    At step  5 - 2 , the interlock detects any sudden change (i.e., increase for negative convention or decrease for positive convention or absolute value) in the torque value during operation. A sudden increase in torque at the torque head  40  indicates a breakout of either one of the top drive connections or the connection between the tubulars  30 ,  65 . The interlock may calculate a derivate of the torque with respect to time or with respect to turns to aid in detecting the sudden increase. A sudden increase in torque may be detected by monitoring the derivative for a change in sign. For example, assuming a negative convention during a breakout operation, the derivative may be a substantially constant negative value until one of the connections breaks. At or near breakout, the derivative will exhibit an abrupt transition to a positive value. Once the breakout is determined, the interlock proceeds to step  5 - 3 . 
         [0057]    At step  5 - 3 , the interlock  749  detects for rotation associated with the sudden change in torque so that the interlock may determine if the breakout is at the connection between the tubulars  30 ,  65  or if the breakout is at one of the top drive connections. If the torque sub  600  is being used, the reading from the sensor  670  will allow the interlock to ascertain where the breakout is. If the breakout is between the torque sub  600  and the top drive  50 , then the quill will rotate while the torque sub remains stationary. If the breakout is at the connection between the tubulars  30 ,  65 , then the torque sub  600  will rotate with the quill and the first tubular  30 . If the either the torque meter  900  or the power input is used to calculate the output torque, then the interlock  749  may use the upper turns counter  905   a  to ascertain where the breakout is. Alternatively or additionally, if the torque meter  900  is used, then the interlock  749  may use the lower turns counter  905   b  to determine if the first tubular  30  is rotating. The interlock  749  may calculate a differential of rotation values or a rotational velocity of the torque sub  600 /torque head  40  and compare the differential rotation/rotational velocity to a predetermined number (i.e., zero or near zero) to determine if the torque sub  600 /torque head  40  is rotating. 
         [0058]    If the interlock  749  determines that the breakout is at one of the top drive connections (i.e., the torque head  40  or the torque sub  600  is not rotating), then the interlock proceeds to step  5 - 4 . At step  5 - 4 , the interlock  749  may then sound an audible alarm and/or display a visual signal to the operator to stop rotation of the top drive  50  to prevent back out of the top drive connections. Additionally or alternatively, the interlock  749  may automatically stop the top drive  50 . If the interlock  749  determines that the breakout is at the tubular connection  30 ,  65 , then the interlock allows the breakout operation to proceed. The interlock may utilize fuzzy logic in performing the control logic of  FIG. 5 . 
         [0059]    In an alternative embodiment (not shown), monitoring output torque of the top drive is not required. This alternative may be performed using the torque sub  600 , torque meter  900 , or upper turns counter  905   a  configurations. This alternative may also be used in addition to the logic of  FIG. 5 . In this alternative, the interlock may monitor readings/calculations from and calculate a differential between the calculated rotation of the top drive and the sensor  670  or the upper turns counter  905   a . Alternatively, the interlock  749  may calculate rotational velocities of the quill and the torque sub  600 /torque head  40  and calculate a differential between the rotational velocities. If the differential is less than (again using a negative convention) a predetermined number, then the interlock  749  may sound/display an alarm and/or halt operation of the top drive. The predetermined number may be set to account for deflection and/or inaccuracy from the calculated rotation value. 
         [0060]    In a second alternative embodiment applicable to make-up systems  700  using the torque sub  600  or the torque meter  900 , the interlock  749  may calculate a differential between the torque value measured from the torque sub  600  or the calculated torque value from the torque meter  900  and the calculated output torque of the top drive  50 . The interlock  749  may also calculate a turns differential as discussed in the first alternative. The interlock  749  may then compare the two delta values to respective predetermined values and sound an alarm and/or halt operation of the top drive  50  if the two delta values are less than the predetermined values. 
         [0061]    In a third alternative embodiment, a strain gage  785  may be bonded to the swivel housing  605  (including the swivel bracket  605   a ) so that the interlock  749  may monitor performance of the swivel bearings. The bearing performance may be monitored during any operation of the top drive, i.e., making up/breaking out connections or drilling (with drill pipe or casing). Discussion of torque relative to the swivel bearings is done assuming right-hand (positive) torque is being applied as is typical for operation of a top drive  50 . This alternative may be performed in addition to any of the breakout monitoring, discussed above. If the swivel bearings should fail, excessive torque may be transferred from the top drive  50  to the bracket  605   a , thereby causing substantial damage to the bracket  605   a  and possibly the swivel  600  as well as creating a hazard on the rig. The strain gage  785  is positioned on the bracket  605   a  to provide a signal  712  to the computer  716  indicative of the torque exerted on the swivel housing  605  by the top drive  50  through the swivel bearings. The interlock  749  may receive the signal  712  and calculate the torque exerted on the swivel housing  605  from predetermined structural properties of the swivel housing. The interlock  749  may calculate a differential between the output torque of the top drive  50  (calculated or measured) and the swivel torque. 
         [0062]    If the bearings are functioning properly, this differential should be relatively large as friction in the bearings (and seals) should only transmit a fraction of the top drive torque. If the swivel bearings should start to fail, this differential will begin to decrease. The interlock  749  may detect failure of the swivel bearings by comparing the differential to a predetermined value. Alternatively, the interlock  749  may calculate a derivative of the differential with respect to time or turns and compare the derivative to a predetermined value. Alternatively, the interlock  749  may divide the swivel torque by the top drive torque to create a ratio (or percentage) and compare the ratio to a predetermined ratio. Failure of the bearing would be indicated by ratio greater than the predetermined ratio. The interlock  749  may only monitor swivel performance above a predetermined output torque of the top drive  50  to eliminate false alarms. In any event, if the interlock  749  detects failure of the swivel bearings, then the interlock  749  may sound/display an alarm and/or halt operation of the top drive  50 . Alternatively, the interlock  749  may compare the calculated torque value to a predetermined value (without regard to the top drive torque) to determine failure of the swivel bearings. 
         [0063]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.