Abstract:
Systems and methods for cooling a Rotating Control Device (RCD) and RCD insert during drilling operations are described. The system includes a body for connection between the RCD and a hot drilling fluid return outlet of a well head, the body including an inlet for injecting cool drilling fluid adjacent the RCD insert and an outlet for removing partially warmed drilling fluid. During operation, cool drilling fluid is circulated through the inlet and outlet such that cool drilling fluid is in direct contact with hot drilling fluid recovered from the well in a buffer zone adjacent the hot drilling fluid return outlet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit under 35 U.S.C. §119 (e) of the U.S. Provisional Patent Application Ser. No. 61/241,317 filed on Sep. 10, 2009. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This application relates to the field of oilfield equipment and more specifically to a Rotating Control Device (RCD) and Cool Fluid Circulation System (CFCS) for managing drilling fluid composition and temperature across the interface of an RCD insert. 
       BACKGROUND OF THE INVENTION 
       [0003]    As is known, in managed pressure applications, there is a need to dynamically and effectively control fluid pressure within a wellbore during drilling. More specifically, it is important to maintain drilling fluid in a wellbore at a pressure less than or equal to the fluid pressure of a geological formation in order to prevent drilling related problems such as stuck pipes, loss of circulation and excessive use of drilling mud. 
         [0004]    Drilling fluid is required during drilling operations to lubricate the drill bit and carry drill cuttings to the surface. Typically, drilling fluid is pumped downwardly through the drill pipe to the drill bit whereupon it returns upwardly to the surface through the wellbore annulus. Drilling fluid returning to the surface will be affected by gravity and friction encountered along the walls of the wellbore thereby increasing the hydrostatic pressure at the bottom of the wellbore. 
         [0005]    Managed Pressure Drilling (MPD) is an adaptive drilling process used to precisely control the annular pressure profile throughout a wellbore. More specifically, MPD allows bottom hole pressure adjustments with minimal interruptions to the drilling process. The annular pressure profile is controlled such that it is balanced or nearly balanced. The objective of MPD is to ascertain the downhole pressure environment limits and to manage the annular hydraulic pressure profile accordingly. 
         [0006]    MPD uses a closed, pressurizable fluid system to control the annular pressure profile. More specifically, the annular pressure in the wellbore is controlled through adjustments in backpressure, fluid density, fluid rheology, annular fluid level, circulating geometry, hole geometry or the like. 
         [0007]    Similarly, Underbalanced Drilling (UBD) uses a closed and pressurizable fluid system wherein the annular wellbore pressure profile is less than the fluid pressure in the formation being drilled. Annular pressure in the wellbore is similarly controlled through adjustments in backpressure, fluid density, fluid rheology, annular fluid level, circulating geometry, hole geometry and the like. 
         [0008]    In order to prevent drilling related problems as described above, MPD and UBD decrease the Equivalent Circulating Density (ECD) by lowering the hydrostatic pressure of drilling fluid. A low density drilling fluid can mitigate the risk of a well becoming overbalanced and developing drilling problems. A gas is often injected into a drilling fluid in order to reduce the drilling fluid density. Some gases commonly used for drilling fluid injection include air, nitrogen, natural gas and processed flue gas. As is known, the use of natural gas and/or processed flue gas may increase the combustible and/or corrosive nature of the drilling fluid. 
         [0009]    Furthermore, in MPD and UBD, drilling fluid is naturally heated while traveling to and from the drill bit by the drilling process and/or geological formations. As a result, drilling fluid often reaches temperatures greater than 65 degrees Celsius (149 degrees Fahrenheit) and can exceed 85 degrees Celsius (185 degrees Fahrenheit). Furthermore, drilling fluid may be comprised of or accumulate combustible and corrosive components during the drilling process. 
         [0010]    As in other drilling operations, managed pressure and underbalanced drilling require a Blowout Preventer (BOP) to prevent an uncontrolled release of formation fluids from the wellbore. A release may cause significant damage to a drilling rig and injuries or fatalities to rig personnel. As a result, MPD and UBD further require that a Rotating Control Device (RCD) be installed on the top of the BOP stack to form a positive pressure seal on the drill pipe and safely divert drilling fluid away from the drill floor. An RCD typically contains a radial insert that forms a seal around the drill pipe. 
         [0011]    As is known, RCD inserts are generally radial and fabricated from synthetic rubber such as neoprene or nitrile rubber. During drilling, the drill pipe is axially forced downwards through the RCD and RCD insert such that over time the RCD insert will incur wear and tear as the insert slidably engages the drill pipe. Thus, as a result of normal use, RCD inserts will deteriorate and become less effective over time. Furthermore, in particular, high temperature drilling fluid and/or any corrosive components of a drilling fluid will accelerate the deterioration of an RCD insert. 
         [0012]    An RCD insert manufacturer will typically recommend a maximum operating lifetime before which RCD inserts should be replaced to ensure safe and productive operation of a drilling rig. The replacement of an RCD insert requires considerable Non Productive Time (NPT) as the drill string must be broken and the RCD disassembled. Accordingly, there continues to be a need for systems that can increase the time between RCD insert replacements. 
         [0013]    As noted, temperature and/or corrosive drilling fluid may cause accelerated deterioration of an RCD insert such that the accelerated deterioration of an RCD insert may cause the premature and/or unexpected failure of the insert before the expiration of the manufacturer recommended maximum operating lifetime. Any premature or unexpected failure can present a significant safety risk to personnel if drilling fluid is released onto the drill floor. 
         [0014]    Thus, while RCD inserts are currently manufactured to resist the corrosive chemical properties or high temperatures of returned drilling fluid, RCD inserts are generally not designed to resist the combination of both the corrosive chemical properties and high temperatures of returned drilling fluids found in many drilling operations. 
         [0015]    More specifically, as is known to one of skill in the art, RCD inserts are generally designed to perform specifically to a recommended maximum operating temperature (typically 65-85° C.). Increases in temperature and/or corrosive drilling fluid compositions can decrease the operating lifetime of an RCD insert. Thus, the maximum operating lifetime of an RCD insert can be extended (and the risk of premature failure reduced) by decreasing the temperature of returned drilling fluid at the RCD insert/drilling fluid interface and/or moderating the composition of returned drilling fluid coming into contact with the RCD insert. 
         [0016]    It is therefore an object of the present invention to improve the useful life of an RCD insert by providing a system and method for lowering the temperature and moderating the composition of returned drilling fluid coming into contact with an RCD insert within an RCD. 
         [0017]    A review of the prior art reveals that a number of technologies have been used in the past for cooling inserts in a Rotating Control Device. For example US Patent Publications 2006/0144622 and 2008/0210471 to Bailey et al. disclose Rotating Control Devices (RCDs) having thermal transfer systems for circulating cooling fluid inside radial RCD seals. 
         [0018]    U.S. Pat. Nos. 6,749,172 and 7,004,444 to Kinder disclose Rotating Control Devices (RCDs) having two independent fluid circuits for cooling and lubrication between a rotating body and the RCD casing. 
         [0019]    Other references include U.S. Pat. No. 5,662,181 which describes circulating chilled water or antifreeze through the top seal packing box of an RCD and U.S. Pat. No. 5,277,249 which describes an RCD having a heat exchanger and fluid circuits for cooling radial seals in a packer assembly. 
         [0020]    While the prior art may provide a partial solution, each are limited in various ways as briefly described below. 
         [0021]    In particular, past systems may be limited as they do not suggest or teach the advantages of a cooling system in which the cooling fluid is in direct contact with the hot drilling fluid. More specifically, previous systems do not suggest a system to prevent hot drilling fluid from directly contacting the radial RCD inserts. Furthermore, previous systems do not teach moderating the composition of drilling fluid across the interface of a radial RCD insert. 
       SUMMARY OF THE INVENTION 
       [0022]    It is the object of the present invention to obviate or mitigate at least one disadvantage of previous rotating control devices and specifically to provide systems and methods that enhance the operating life of an RCD insert within an RCD. 
         [0023]    In accordance with a first embodiment of the invention, there is provided a cool fluid circulation system (CFCS) for circulating cool drilling fluid across a rotating control device (RCD) and RCD insert operatively connected to a well head having a hot drilling fluid return outlet, the CFCS comprising: a body for operative connection between the RCD and the hot drilling fluid return outlet at the well head, the body including an inlet for injecting cool drilling fluid adjacent the RCD insert and an outlet for removing partially warmed drilling fluid; wherein the cool drilling fluid is in direct contact with hot drilling fluid in a buffer zone adjacent the hot drilling fluid return outlet. 
         [0024]    In further embodiments, the CFCS includes a void space above the inlet and outlet for containing and circulating a volume of cool drilling fluid adjacent the RCD insert and/or a second void space below the inlet and outlet for containing and circulating a volume of cool drilling fluid adjacent an interface with hot drilling fluid. 
         [0025]    In another embodiment, the invention provides a system for circulating cool drilling fluid across a rotating control device (RCD) and RCD insert operatively connected to a well head having a hot drilling fluid return outlet, the CFCS comprising: a body for operative connection between the RCD and the hot drilling fluid return outlet at the well head, the body including an inlet for injecting cool drilling fluid adjacent the RCD insert and an outlet for removing partially warmed drilling fluid; wherein the cool drilling fluid is in direct contact with hot drilling fluid adjacent the hot drilling fluid return outlet; and, a cool drilling fluid circulation system operatively connected to the inlet for injecting cool drilling fluid into the inlet and for removing partially warmed drilling fluid from the outlet. 
         [0026]    In a further embodiment, the system includes a choke system for controlling the flow rate and pressure of cool drilling fluid within the cool drilling fluid circulation system and will preferably include at least one temperature sensor operatively connected to the body for measuring the temperature of cool drilling fluid within the body and/or at least one pressure sensor operatively connected to the body for measuring the pressure of cool drilling fluid within the body. 
         [0027]    In a further embodiment, the system includes a control system operatively connected to the temperature sensor and pressure sensor for automatically controlling the flow rate of cool drilling fluid within the cool drilling fluid circulation system in response to measured temperatures and pressures in the cool drilling fluid circulation system. 
         [0028]    In another aspect, a method is described for circulating cool drilling fluid across a rotating control device (RCD) having an RCD inlet and an RCD outlet and RCD insert, the RCD operatively connected to a well head having a hot drilling fluid return outlet, the method comprising the step of: circulating a volume of cool drilling fluid adjacent the RCD insert through the RCD inlet and outlet wherein the cool drilling fluid is in direct contact with hot drilling fluid adjacent the hot drilling fluid return outlet. 
         [0029]    In further embodiments of the method, the cool drilling fluid recovered from the RCD outlet is subjected to a cooling process prior to recirculating cool drilling fluid into the RCD inlet. 
         [0030]    In yet another embodiment, the cool drilling fluid recovered from the RCD outlet is subjected to a solids separation process prior to recirculating cool drilling fluid into the RCD inlet. 
         [0031]    In yet another embodiment, the temperature of the cool drilling fluid recovered from the RCD outlet is monitored and the flow rate of the cool drilling fluid is adjusted through the RCD to ensure adequate cooling of the RCD insert. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    The invention is described with reference to the accompanying figures in which: 
           [0033]      FIG. 1  is a cross sectional view of a Rotating Control Device and Cool Fluid Circulation System (CFCS) having a cool drilling fluid inlet and outlet in accordance with one embodiment of the invention. 
           [0034]      FIG. 2  is a schematic diagram of a primary circulation system and cool drilling fluids circulation system in accordance with one embodiment of the invention; and, 
           [0035]      FIG. 3  is a schematic representation of a decision making process for controlling the pressure of cool drilling fluid in accordance with one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    As used herein, the term “returned drilling fluid”  30  refers to all fluids, solids and gases in a drilling operation that have been returned to the surface through a wellbore  40  including drilling fluid, drill cuttings, oil and the like. 
         [0037]    Overview 
         [0038]    With reference to the figures, the present invention generally relates to a system enabling the circulation of cool drilling fluid through a Rotating Control Device (RCD)  10  and RCD insert  14 . The device and its control system are particularly useful in managed pressure or underbalanced well drilling. 
         [0039]    As known, an RCD  10  and RCD insert  14  generally seals around and rotates with a drill pipe  24  to prevent drilling fluid circulating through the annulus from escaping onto the drill floor. In addition, the RCD  10  and RCD insert  14  permits the drill pipe  24  to slide into and out of the wellbore while maintaining a tight seal on the drill pipe  24 . Within known systems, a main drilling fluid outlet  28  at the well head allows drilling fluid to be removed from the annulus of the well for drill cutting removal and re-use. In various applications, a well incorporating an RCD may include other systems for enhancing the hydraulic pressure seal and/or to provide other functions to and around a drill pipe  24  as known to those skilled in the art. 
         [0040]    In accordance with the invention, the RCD further includes a cool fluid circulation system (CFCS)  15  for operative connection between the RCD and main drilling fluid outlet  28  of the well. The CFCS  15  includes a cool drilling fluid inlet  18  and cool drilling fluid outlet  20  that enables the circulation of cool drilling fluid  16  across the lower surfaces of the RCD insert  14  and within an RCD cavity  22 . In accordance with the objects of the present invention, the circulation of cool drilling fluid  16  across the lower surfaces of the RCD insert  14  lowers the temperature and moderates the composition of drilling fluid in the RCD cavity  22  thereby slowing the deterioration of the RCD insert  14 . As a result, the present invention will increase the maximum operating lifetime and mitigate the risk of premature failure of an RCD insert  14 . 
         [0041]    In addition, the present invention further includes external fluid circuits for circulating drilling fluids and cool drilling fluids ( FIG. 2 ). A first drilling fluid circuit  400  withdraws returned drilling fluid from the wellbore and inserts recycled drilling fluid down the drill pipe  24 . A second drilling fluid circuit  200  circulates cool drilling fluid  16  across the interface of the RCD insert within the rotating control device  10 . A control system  500  monitors the circulation of drilling fluids ( FIG. 3 ). 
         [0042]    Rotating Control Device and Cool Fluid Circulation System 
         [0043]      FIG. 1  generally describes an RCD  10  which as known to those skilled in the art includes a body  12  and a bearing assembly (not shown) retained within the body  12  that rotates with drill pipe  24  and that operatively supports the RCD insert. The bearing assembly is operationally located between the RCD body  12  and a drill pipe  24  so as to permit rotational movement of the RCD insert with respect to the body. As known, the drill pipe  24  will pass through the top of the RCD body  12 , RCD insert  14  and into the wellbore. 
         [0044]    As shown in  FIGS. 1 and 2 , returned drilling fluid  30  flowing upwardly within the annular column  12   a  is withdrawn through an outlet  28  into a first fluid circuit  400 . During Managed Pressure or Underbalanced drilling that does not include a CFCS  15 , the returned drilling fluid  30  fills the RCD cavity  22  and is in direct contact with the RCD insert  14 . 
         [0045]    In accordance with the invention, the CFCS  15  includes a cool drilling fluid inlet  18  and cool drilling fluid outlet  20  operationally connected to the RCD below the RCD insert  14 . Both the inlet  18  and outlet  20  are connected to the cool drilling fluid circulation system  200 . The inlet  18  and outlet  20  are diametrically opposite each other and are located above the returned drilling fluid outlet  28  in the annulus  12   a.    
         [0046]    In operation, cool drilling fluid  16  enters the CFCS through the cool drilling fluid inlet  18  to create a buffer zone  22   a  of cool drilling fluid between the returned drilling fluid and the RCD insert. The inlet  18  is positioned to generally direct cool drilling fluid  16  across the interface of the RCD insert  14  such that the buffer zone  22   a  prevents returned drilling fluid  30  from directly contacting the RCD insert  14 . A cool drilling fluid outlet  20  is positioned opposite to the inlet  18  in order to withdraw cool drilling fluid  16  from the buffer zone and RCD cavity  22 . 
         [0047]    Importantly, the temperature and pressure of drilling fluid within the buffer zone  22   a  can be controlled and any abrasive or corrosive components of returned drilling fluid  30  will be substantially prevented from contacting the RCD insert  14 . In other words, the combined design of the RCD  10 , the CFCS  15  and the operational temperature and pressure of cool drilling fluid  16  are designed and controlled to prevent substantive mixing and diffusion of returned drilling fluid  30  into the RCD cavity  22  so as to provide maximum cooling and fluid composition moderation across the lower surfaces of the RCD insert. 
         [0048]    Primary Drilling Fluid Circulation System and Cool Fluids Circulation System 
         [0049]    With reference to  FIG. 2 , the invention further provides a system enabling the use of the CFCS within a drilling operation. The system includes a primary drilling fluids circulation system  400  and a cool fluids circulation system  200  for operative connection to the CFCS. 
         [0050]    The primary drilling fluids circulation system (primary fluid circuit)  400  enables downhole pumping of drilling fluid, surface recovery of returned drilling fluid, surface cleaning and separation of returned drilling fluid, chemical modification of drilling fluid and re-circulation of returned drilling fluid  30 . Within the primary fluid circuit, drilling fluids are pumped down the drill pipe to the drill bit, and returned upwardly to the surface between the drill pipe and wellbore  40  where the returned drilling fluid is withdrawn through the annular outlet  28 . At surface, the primary fluid circuit  400  includes piping  420 , storage tanks  402  and pumps  404  as required for the operation of the primary fluid circuit  400 . 
         [0051]    In addition, as it is desirable to remove undesirable components such as drill cuttings and oil from the returned drilling fluid  30  before the recirculation of drilling fluid down the drill pipe  24 , the primary fluid circuit  400  will typically include a separation system  418  for removing drill cuttings, oil and other contaminants from the returned drilling fluid  30 . The separation system may include components such as a shale shaker, sedimentation tanks, chemical processing, and/or cleaning systems and the like in order that clean drilling fluid  30  is reused and pumped down the drill pipe  24 . 
         [0052]    The primary fluid circuit  400  will further include appropriate manifolds  416 , valves  406  and choking devices  412  to enable control of the pressure and flow of drilling fluid  30  and/or chemical injection/adjustment within the system. Other systems may include gas injection  430  as well as standard well kill systems including pump  432  and kill mud tanks  432   a.    
         [0053]    The primary fluid circuit will also include appropriate temperature  422  and pressure sensors  424  to monitor drilling fluid properties. 
         [0054]    The cooling fluid circulation system (cool fluid circuit)  200  is provided to insert cool drilling fluid  16  into the cool drilling fluid inlet  18  and withdraw drilling fluid from cool drilling fluid outlet  20 . The cool fluid circuit  200  includes piping  220 , a fluids handling system operating in conjunction with the separation system  418  and appropriate pumps  204  as required for the operation of the cooling fluid circulation system. Appropriate valves  206  are also provided to stop or redirect cool drilling fluid  16  flow as may be desired within a specific system. 
         [0055]    Operation 
         [0056]    Generally, in operation, in order to provide effective RCD insert cooling, it is necessary to balance the pressure and flow rate of cool drilling fluid  16  circulating in the RCD cavity. For example, insufficient cool drilling fluid  16  pressure and flow would generally cause the temperature of RCD insert  14  to rise whereas conversely, high pressure cool drilling fluid  16  may cause undesirable mixing and diffusion between the cool drilling fluid  16  and the returned drilling fluid  30 . 
         [0057]    As a result, as the pressure of returned drilling fluid  30  may change over time, a choking device  212  may be installed downstream of the RCD outlet  20  in order to control the pressure of cool drilling fluid  16  within the RCD. Choking device  212  can be adjusted to increase or decrease the flow of cool drilling fluid  16  as required to maintain a desired pressure and flow of cool drilling fluid within the RCD cavity  22 . 
         [0058]    The cool fluid circuit  200  may further include appropriate sensors to monitor drilling fluid  16  characteristics such as the temperature and pressure within the circuit. In a preferred embodiment, temperature  208  and pressure  210  sensors are located at the cool drilling fluid inlet  18  and outlet  20  to the RCD  10 . The system will also preferably include emergency release piping  420  to enable effective diversion in the event of an emergency as well as equalization and bleed-off piping  600  as known to those skilled in the art. 
         [0059]    In another embodiment, the cooling fluid circulation system  200  may include a refrigeration system (not shown) for actively or passively cooling drilling fluids. 
         [0060]    Control System 
         [0061]    The RCD, primary fluid circuit  400  and cooling fluid circulation system  200  may be monitored and controlled by a control system  500 . In a preferred embodiment, the control system  500  is electronic and operationally connected to appropriate temperature sensors  214 ,  424 , pressure sensors  216 ,  426 , valves  206 ,  406  and choking devices  212 ,  412  in order to enable effective control of the system during drilling. 
         [0062]    In one embodiment, temperature and pressure sensors operationally transmit temperature and pressure data to the control system. The control system may decide to increase or decrease fluid pressure within the primary fluid circuit  400  or cooling fluid circulation system  200  as required for drilling and the optimal operation of the RCD  10  and CFCS  15 . More specifically, the control system may instruct a choking device  212 ,  412  to increase or decrease fluid pressure in the desired fluid circuit. 
         [0063]    Referring to  FIG. 3 , a preferred embodiment of a control decision structure is provided. By way of example, the electronic interface may take a temperature reading at the RCD outlet  502  and determine if the temperature is too high  506 . If the temperature is too high, the control system will take steps to increase cool drilling fluid pressure  510 . Increased cool drilling fluid pressure may be provided by closing a choking device  212  or increasing pump pressure  204 . Conversely, if the temperature reading at the outlet  502  is not too high, the control system will evaluate if the pressure reading at the RCD outlet  504  is too high  508 . If the pressure reading  504  at the outlet is too high, the control system will reduce the pressure of cool drilling fluid  512 . If the pressure is not too high, no adjustments will be made by the control system  514 . 
         [0064]    Similar embodiments can be realized by alternate positioning of sensors and control decision structures. 
         [0065]    Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.