Abstract:
A rotating control device (RCD) for use with a drilling unit includes a body having a flange formed at an end thereof for coupling to the drilling unit; a seal assembly for receiving and sealing against a tubular; a bearing assembly for supporting rotation of the seal assembly relative to the body; a releasable connection connecting the bearing assembly to the body; a transmitting assembly rotatable with the seal assembly; and a receiving assembly attached to a non-rotating portion of the RCD.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0001]    Embodiments of the present invention generally relate to a rotating control device. More particularly, embodiments of the present invention relate to an apparatus and a method of transmitting data from a rotating control device. 
       Description of the Related Art 
       [0002]    Drilling a wellbore for hydrocarbons requires significant expenditures of manpower and equipment. Thus, constant advances are being sought to reduce any downtime of equipment and expedite any repairs that become necessary. Rotating equipment is particularly prone to maintenance as the drilling environment produces abrasive cuttings detrimental to the longevity of rotating seals, bearings, and packing elements. 
         [0003]    In a typical drilling operation, a drill bit is attached to a drill pipe. Thereafter, a drive unit rotates the drill pipe using a drive member as the drill pipe and drill bit are urged downward to form the wellbore. Several components are used to control the gas or fluid pressure. Typically, one or more blow out preventers (BOP) is used to seal the mouth of the wellbore. In many instances, a conventional rotating control device is mounted above the BOP stack. An internal portion of the conventional rotating control device is designed to seal and rotate with the drill pipe. The internal portion typically includes an internal sealing element mounted on a plurality of bearings. The internal sealing element may consist of a first seal arrangement on a lower portion of the rotating control device and a second seal arrangement on an upper portion of the rotating control device. Over time, the lower seal arrangement may leak (or fail) due to wear, which only leaves the upper seal arrangement to seal and rotate with the drill pipe. 
         [0004]    It is important for an operator to know when the lower seal arrangement in the rotating control device is leaking because if the upper seal arrangement leaks or fails, then the wellbore fluid will be released in the surrounding environment. This is particularly important in an offshore drilling operation where the rotating control device is disposed below the rig in the surrounding seawater. A problem arises when data about the operation of the rotating control device is to be sent to the operator. The problem results from the fact that data cannot be effectively transmitted from the rotating control device to the operator due to the surrounding seawater. There is a need therefore, for an apparatus and method for data transmission from a rotating control device. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention generally relates to an apparatus and a method of transmitting data from a rotating control device. In one aspect, a method of transmitting data from a rotating control device coupled to an offshore drilling unit is provided. The method includes the step of generating data relating to a parameter associated with the rotating control device. The method further includes the step of transmitting the data from a transmitting assembly coupled to the rotating control device to a receiving assembly positioned proximate the transmitting assembly. Additionally, the method includes the step of transmitting the data from the receiving assembly to the offshore drilling unit. 
         [0006]    In another aspect, a data gathering and transmitting system for use with a rotating control device coupled to an offshore drilling unit is provided. The system includes a transmitting assembly coupled to the rotating control device, the transmitting assembly configured to generate data relating to a parameter associated with the rotating control device and transmit the data. The system further includes a receiving assembly disposed proximate the transmitting assembly, wherein the receiving assembly is configured to receive the data sent by the transmitting assembly and relay the data to the offshore drilling unit. 
         [0007]    In a further aspect, a method for transmitting data generated in a rotating control device coupled to a riser is provided. The rotating control device includes at least two sealing assemblies. The method includes the step of generating data associated with a location between the at least two sealing assemblies in the rotating control device. The method further includes the step of transmitting the data to a receiving assembly attached to the riser. Additionally, the method includes the step of analyzing the data to determine if there is a leakage from at least one of the two sealing assemblies. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    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. 
           [0009]      FIG. 1  is a view illustrating a rotating control device. 
           [0010]      FIG. 2  is a cross-sectional view illustrating the rotating control device with a data gathering and transmitting system. 
           [0011]      FIG. 3  is an enlarged view illustrating the data gathering and transmitting system. 
           [0012]      FIG. 4  is a view illustrating the data gathering and transmitting system. 
           [0013]      FIG. 5  is a view illustrating a portion of the upper rotating section. 
           [0014]      FIGS. 6A and 6B  are views illustrating the flange of a body of the rotating control device. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The present invention generally relates to an apparatus and a method of transmitting data from a rotating control device. The invention will be described in relation to an offshore drilling operation that has rotating control device coupled to a riser. It is to be noted, however, that the invention may be used in an offshore drilling operation that does not use a riser without departing from principles of the present invention. To better understand the aspects of the present invention and the methods of use thereof, reference is hereafter made to the accompanying drawings. 
         [0016]      FIG. 1  is a view illustrating a rotating control device  75  coupled to a riser  10 . As illustrated, the rotating control device  75  is connected to a Blow Out Preventer (BOP) stack  15  via a first riser portion  40 . The BOP stack  15  is typically used to ensure pressure control in the riser system  10 . The rotating control device  75  is also connected to a diverter  20  via a second riser portion  50 . This arrangement may be used in a managed pressure drilling (MPD) operation. Generally, MPD is a form of well control, which uses a closed, pressurizable fluid system that allows greater, and more precise control of a wellbore pressure profile than mud weight and mud pump rate adjustments alone. Some examples of MPD are constant bottom hole pressure drilling, dual gradient drilling and pressurized mud cap drilling. 
         [0017]    During the MPD operation, drilling fluid (mud) is pumped down a drill string located in the riser and the return fluid is communicated from the riser to a drilling fluid receiving device. The return fluid is communicated from the riser via an outlet  45  in the rotating control device  75  and suitable conduits attached thereto when a bearing assembly with one or more seals is disposed in the rotating control device  75 . If the bearing assembly has been removed from the rotating control device  75 , then the return fluid is communicated from the riser via the diverter  20 . 
         [0018]    In an alternative embodiment, the data gathering and transmitting system  100  ( FIG. 2 ) may be used on the rotating control device  75  while drilling an offshore well without a continuous riser present between the rotating control device  75  and the drilling rig. In this arrangement, the riser portion  50  may be absent and/or there may be only a short riser section located below the diverter  20 , which does not extend all the way down to the rotating control device  75 . Preferably, drilling returns are still routed back to the rig via the outlet  45  and suitable conduits attached thereto. In this instance the signals from the data gathering and transmitting system  100  may be conveyed back to the rig via fiber optic, electrical, pneumatic, hydraulic or any other suitable transmission line attached to (or gathered with) the drilling returns conduits. Alternatively, the signals from the data gathering and transmitting system  100  may be conveyed back to the rig via fiber optic, electrical, pneumatic, hydraulic or any other suitable transmission line attached to (or gathered with) other conduits or control umbilicals, such as those associated with the BOP stack  15 . 
         [0019]    In a further alternative embodiment, the drilling fluid returns may be routed back to the rig via the outlet  45 , suitable conduits attached thereto, plus an assisted lifting system such as a pump system (not shown) that provides a pressure boost to the returns in order to assist the flow back to the rig. Such a pump system is described in U.S. Pat. No. 6,415,877, which is incorporated herein by reference in its entirety. The pump system may be located at or near the seabed, or (if a riser is present) attached to the riser at an appropriate location. In this instance the signals from the data gathering and transmitting system  100  may be conveyed back to the rig via fiber optic, electrical, pneumatic, hydraulic or any other suitable transmission line attached to (or gathered with) the drilling returns conduits or other conduits or control umbilicals associated with the pump system. Similarly, a gas lift system (not shown) may be used in addition to, or in place of, the pump system in order to assist with conveying the drilling fluid returns to the rig. The signals from the data gathering and transmitting system  100  may be conveyed back to the rig via fiber optic, electrical, pneumatic, hydraulic or any other suitable transmission line attached to (or gathered with) conduits or control umbilicals associated with the gas lift system. 
         [0020]    In another embodiment, methods and apparatus may be used to transmit data from a rotating control device  75  to an offshore drilling unit. Exemplary offshore drilling units include jackup rigs, semi-submersibles, drill ships, drilling barges, and drilling platforms. 
         [0021]      FIG. 2  is a cross-sectional view illustrating the rotating control device  75  with a data gathering and transmitting system  100 . The rotating control device  75  includes a first seal assembly  55  and a second seal assembly  65  that forms a continuous seal around a tubular  85 , such as a drill pipe, to contain the wellbore pressure. Each seal assembly  55 ,  65  includes components that rotate with respect to a body  25  of the rotating control device  75 . The components that rotate in the rotating control device  75  are mounted for rotation on a bearing assembly  60 . 
         [0022]    As depicted, the first seal assembly  55  is disposed in the body  25  of the rotating control device  75 . The first seal assembly  55  is mounted to the bearing assembly  60 . The first seal assembly  55  is constructed and arranged in an axially downward conical shape, thereby allowing a pressure to act against a tapered surface  80  to close the first seal assembly  55  around the tubular  85 . Additionally, the first seal assembly  55  includes an inner diameter smaller than the outer diameter of the tubular  85  to allow an interference fit between the tubular  85  and the first seal assembly  55 . 
         [0023]    In another embodiment, the first seal assembly  55  includes a bladder (not shown) mounted on the support housing. In this embodiment, hydraulic fluid is used to activate the first seal assembly  55 . For instance, the bladder is configured to move radially inward to create an active seal around the tubular  85  upon application of hydraulic fluid. In this manner, the bladder can expand to seal off a borehole through the rotating control device  75 . Additionally, the bladder is configured to release the active seal around the tubular  85  when the application of hydraulic fluid is reduced. 
         [0024]    The second seal assembly  65  is disposed above the first seal assembly  55 . The second seal assembly  65  is part of an upper rotating section  105  that is operatively attached to the bearing assembly  60 , thereby allowing the second seal assembly  65  to rotate with the first seal assembly  55 . Fluid is not required to operate the second seal assembly  65  but rather it utilizes pressure in the rotating control device  75  to create a seal around the tubular  85 . The second seal assembly  65  is constructed and arranged in an axially downward conical shape, thereby allowing the pressure to act against a tapered surface  90  to close the second seal assembly  65  around the tubular  85 . Additionally, the second seal assembly  65  includes an inner diameter smaller than the outer diameter of the tubular  85  to allow an interference fit between the tubular  85  and the second seal assembly  65 . 
         [0025]    The data gathering and transmitting system  100  includes a transmitting assembly  175  that is in communication with a receiving assembly  275 . Generally, the transmitting assembly  175  is configured to generate data relating to a parameter in the rotating control device  75  and then send a data signal to the receiving assembly  275 . The receiving assembly  275  is configured to receive the data signal and then relay the data signal to a controller or an operator. The controller may be part of the receiving assembly  275  or the controller may be located at the surface. In either case, the controller is used to analyze or process the data signal. Further, in another embodiment, there may be more than one transmitting assembly  175  and/or receiving assembly  275  to provide redundancy. 
         [0026]      FIG. 3  is an enlarged view illustrating the data gathering and transmitting system  100 . Generally, the transmitting assembly  175  comprises a module  150 , a sensing member  145 , and a transmitting antenna  110 . The upper rotating section  105  includes a module pocket  160  that is configured to house the module  150  and a sensing pocket  165  ( FIG. 5 ) for housing the sensing member  145 , such as a transducer. The sensing member  145  is configured to measure data in the rotating control device  75  and then the module  150  communicates the data via the transmitting antenna  110  to the receiving assembly  275 . The data may be pressure, temperature, RPM, flow rate or fluid type data. For instance, if the data is pressure, then the sensing member  145  measures the pressure data between the first seal assembly  55  and the second seal assembly  65  in a pathway  135 . The data may be used to indicate that there is a leak in the first seal assembly  55 . For example, if the pressure data between the first seal assembly  55  and the second seal assembly  65  increases, that may indicate that the first seal assembly  55  is leaking. Additionally, temperature data may be used in conjunction with pressure data and/or RPM data to determine if fluid is leaking past the first seal assembly  55 . The data may also be used to determine if the bearing assembly  60  is operating properly. For instance, the temperature data may be used in conjunction with the RPM data to determine if the bearing assembly  60  is about to fail. In the embodiment shown in  FIG. 3 , the transmitting assembly  175  is disposed in the upper rotating section  105 . In another embodiment, the transmitting assembly  175  may be disposed in a non-rotating portion of the rotating control device  75 . In this embodiment, a communication port (not shown) is formed in the upper rotating section  105  to allow data communication between the transmitting assembly  175  and the receiving assembly  275 . 
         [0027]    In another embodiment, the data gathering and transmitting system  100  may include an acoustic sensor (not shown) that measures acoustic data. The measured acoustic data may be compared to predetermined data relating to normal acoustic data to determine if there is an abnormality. For instance, the bearing assembly  60  may generate normal acoustic data when the bearing assembly  60  is functioning correctly and the bearing assembly  60  may generate a different acoustic data when the bearing assembly  60  is about to fail. When a change in the acoustic data is detected, then the operator is alerted that the bearing assembly  60  is about to fail. The acoustic sensor may also be used to determine when the seal in the first seal assembly  55  is about to fail by comparing a normal acoustic data generated when the seal assembly  55  is functionally properly to a different acoustic data when the first seal assembly  55  is about to fail. 
         [0028]    The upper rotating section  105  further includes an antenna pocket  155  ( FIG. 4 ) that is configured to house the transmitting antenna  110 . The transmitting antenna  110  is in communication with the module  150  and the transmitting antenna  110  is configured to transmit the data generated by the module  150 . In one embodiment, the transmitting antenna  110  is positioned in a flanged portion of the upper rotating section  105  such that the transmitting antenna  110  is located adjacent an inner surface of the body  25  and still be protected. In another embodiment, the transmitter assembly  175  is sealed to withstand pressure, such as at least 50 PSI, preferably at least 200 PSI. 
         [0029]    As also shown in  FIG. 3 , the body  25  includes a flange  200  for use with the receiving assembly  275 . Generally, the receiving assembly  275  comprises an electronic system  280  and a receiving antenna  205  which are also part of the data gathering and transmitting system  100 . The flange  200  includes an antenna pocket  215  that is configured to house the receiving antenna  205 . The receiving antenna  205  is configured to receive a data stream (e.g. RF signal) transmitted by the transmitting antenna  110 . In one embodiment, the receiving antenna  205  is positioned adjacent an inner surface of the flange  200  to allow the receiving antenna  205  to be at a suitable proximity from the transmitting antenna  110 . In another embodiment, the receiving antenna  205  is spaced apart from the transmitting antenna  110  approximately 3.5 inches. 
         [0030]    The flange  200  further includes an electronic system pocket  220  that is configured to house the electronic system  280 . The electronic system  280  is in communication with the receiving antenna  205 . The electronic system  280  may be configured to communicate the data to a controller or an operator via a wire, fiber optic, electrical, pneumatic, hydraulic or any other suitable transmission line. In another embodiment, the data is communicated via acoustic signals through the surrounding seawater. A suitable receiver at the surface will receive the acoustic signals. 
         [0031]    In another embodiment, the electronic system  280  may be configured to act as a repeater (or a relay station) which communicates the data to a receiver via a RF signal. In a further embodiment, the receiving assembly  275  is sealed to withstand pressure, such as at least 50 PSI, preferably at least 200 PSI. In another embodiment, the flange  200  is positioned such that the transmitting antenna  110  is located substantially next to the receiving antenna  205 . 
         [0032]    In one embodiment, the distance between the receiving antenna  205  and the transmitting antenna  110  is kept to a minimum to ensure communication through potentially conductive liquid. For instance, a RF signal is attenuated in liquid or air. However, transmission through a liquid is strongly dependent upon the conductivity of the liquid medium. In general, attenuation increases in liquids with higher conductivity. As compared to water, air is not conductive. Typically, the data gathering and transmitting system  100  can transmit the RF signal up to 3000 ft. in air. Conductive constants of wellbore liquids may vary. For example, water has 0.0546 mhos/m and seawater has 2-8 mhos/m (depending on salinity). 
         [0033]    RF signals are strongly attenuated in highly conductive liquids. Typically, the data gathering and transmitting system  100  has a frequency between 900-925 MHz and a signal loss up to 90 db can be tolerated. For water, the signal loss due to attenuation is approximately 121 db/m. However, for seawater, signal loss due to attenuation is approximately 735 db/m at 2 mhos/m, 1160 db/m at 4 mhos/m, and 1470 db/m at 8 mhos/m. Since saltwater is most demanding, the distance between the receiving antenna  205  and the transmitting antenna  110  is kept to a minimum to ensure communication, such as from 0.1 to 15 inches; preferably, from 1 to 8 inches; and more preferably, from 2 to 4 inches of each other (for 4 mhos/m conductivity). 
         [0034]    In another embodiment, the signal strength of the data transmitted may indicate the condition of the rotating control device  75 . For example, the signal strength may be an indication of the distance from the transmitter assembly to the receiver assembly. In this respect, variations in the signal strength may indicate that the upper rotating section  105  is wobbling within the rotating control device  75  during rotation. Any increase in wobbling during the operation may indicate the onset of a problem (e.g. failure of a component). 
         [0035]    In another embodiment, data relating to the parameters may be correlated to occurrences or patterns of failure. These patterns, when established, may be used in a predictive capacity. In this respect, the patterns may be used to predict the failure of a component of the rotating control device. Thus, a repair or replacement may be performed or scheduled prior to the failure occurring. 
         [0036]    The data gathering and transmitting system  100  may be used to facilitate the positioning of a replacement bearing assembly in the body  25 . The bearing assembly  60  of the rotating control device  75  includes the upper rotating section  105  and the lower rotating section  125 . The bearing assembly  60  is connected to the body  25  by a releasable connection  30  ( FIG. 2 ). In one embodiment, the releasable connection  30  is a dog and piston arrangement, whereby the dog can be selectively moved into engagement with a portion of the rotating control device  75 . The releasable connection  75  allows the bearing assembly  60  of the rotating control device  75  to be removed from the body  25  and replaced with a similar arrangement. As the replacement, bearing assembly is lowered into the body  25 , the transmitting assembly  175  of the data gathering and transmitting system  100  may be used to determine the position of the bearing assembly  60  in the body  25 . As the bearing assembly is lowered into the body  25 , the transmitting assembly  175  sends out a signal. Since the body  25  is filled with fluid, the signal from the transmitting assembly  175  is attenuated and cannot be received by the receiving assembly  275  until the transmitting assembly  175  is positioned proximate the receiving assembly  275  which also indicates the position of the bearing assembly within the body  25  section. After determining the proper positioning, the bearing assembly may be connected to body  25  by the releasable connection  30 . 
         [0037]    As illustrated, the rotating control device  75  includes the first seal assembly  55  and the second seal assembly  65 . In another embodiment, the rotating control device  75  includes a single seal assembly (not shown) and the sensing member may generate data associated with the rotating control head  75  above and/or below the single seal assembly. 
         [0038]    In another alternative embodiment, the receiving assembly  275  may be replaced or augmented by a receiving assembly attached to or contained within the tubular  85 . In this arrangement, the tubular  85  further comprises suitable data transmission equipment; in an exemplary embodiment tubular  85  comprises wired drill pipe. The data signals may therefore be conveyed back to the rig via the wire in the wired drill pipe. In this embodiment, tubular  85  may comprise more than one receiving assembly, preferably spaced apart vertically such that data may be acquired intermittently, at suitable time intervals, i.e. whenever any receiver is in the vicinity of the transmitting assembly  175 . 
         [0039]      FIG. 4  is a view illustrating the data gathering and transmitting system  100 . For clarity, the second seal assembly  65  and the tubular  85  are not shown. A portion of the upper rotating section  105  and the flange  200  of the body  25  have been cut away to illustrate the relationship between the transmitting assembly  175  and the receiving assembly  275 . As shown, the transmitting assembly  175  is spaced apart from the receiving assembly  275 . The transmitting assembly  175  may include a first plate  185  to cover (and/or seal) the module pocket  160  and a second plate  190  to cover (and/or seal) the antenna pocket  155 . In a similar manner, the receiving assembly  275  may include a second cover plate  290  to cover (and/or seal) the electronic system pocket  220  and another cover plate  230  ( FIG. 3 ) configured to cover (and/or seal) the antenna pocket  215 . In one embodiment, the plates  185 ,  190  and the covers  230 ,  290  are made from a composite or polymer material, such as Delrin®. In another embodiment, the plate  190  and/or the cover plate  230  may include metal shielding plates to aid the transmission of the signal between the transmitting assembly  175  and the receiving assembly  275 . This embodiment may be useful in the placement of the replacement bearing assembly in the body  25  as discussed herein. 
         [0040]      FIG. 5  is a view illustrating a portion of the upper rotating section  105 . For clarity, the first and second plates have been removed. As shown, the upper rotating section  105  includes the antenna pocket  155  for housing the transmitting antenna  110 . As illustrated, the transmitting antenna  110  is located on a portion of the circumference of the upper rotating section  105 . In this arrangement, the transmitting antenna  110  is positioned proximate the receiving antenna  205  in the flange  200  for a certain amount of time during each rotation of the rotating section  105 . In another embodiment, the transmitting antenna  110  is a circumferential antenna array and therefore the transmitting antenna  110  is positioned proximate the receiving antenna  205  in the flange  200  the entire time during each rotation of the rotating section  105 . In a further embodiment, the receiving antenna  205  is a circumferential antenna array disposed around the inner surface of the flange  200 . In yet a further embodiment, the transmitting antenna  110  and the receiving antenna  205  are a circumferential antenna array. 
         [0041]    As also shown, the upper rotating section  105  includes the module pocket  160 . As further shown, the upper rotating section  105  includes a power supply pocket  180  configured to house a power supply (not shown), such as a battery, which supplies power to the components of the data gathering and transmitting system  100 . Further, a switch (not shown) may used in the data gathering and transmitting system  100  for controlling the power supply or the module. The switch may be a discrete switch or part of the power supply or the module. Additionally, as shown, the upper rotating section  105  may further include a sensing member pocket  165  configured to house the sensing member (not shown) that may be used to measure data. 
         [0042]      FIGS. 6A and 6B  are views illustrating the flange  200  of the body  25 . For clarity, the cover plates are not shown. In  FIG. 6A , the antenna pocket  215  is illustrated and in  FIG. 6B , the electronic system pocket  220  is illustrated. As shown in  FIGS. 6A and 6B , the flange  200  is part of the body  25 . In another embodiment, a separate component, such as a riser spacer (not shown), may be connected to the body  25 . In this embodiment, the riser spacer would be used in place of the flange  200  of the body  25  to house the receiving assembly. 
         [0043]    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.