Abstract: A drilling system, rotating control device, and a method for accessing a wellbore may employ a rotating control device arranged to form a dynamic seal between the housing and an exterior of the string to isolate the wellbore annulus under both a positive and a negative differential pressure across the seal. The rotating control device may including a sleeve rotatively disposed within the housing and rotatively carried near a longitudinal midpoint of the sleeve by a thrust bearing assembly. One or more seal retainers may be coupled to and sealed against the sleeve, each including a resilient element disposed to slide to a first sealing position within the seal retainer under a positive differential pressure across the element and to slide to a second sealing position within the seal retainer under a negative differential pressure across the element.

Abstract: A method of mitigating undesired pressure variations in a wellbore due to movement of a well tool string in a well can include selectively decreasing and increasing fluid communication between sections of a wellbore on opposite sides of at least one well tool in the well tool string, the fluid communication being increased in response to detecting a threshold movement of the well tool string relative to the wellbore. A well tool string can include a well tool connected in the well tool string, and having an enlarged outer dimension relative to adjacent sections of the well tool string, a flow passage extending between the well tool's opposite ends, a sensor, and at least one flow control device which selectively permits and prevents fluid communication between the opposite ends via the flow passage, in response to an output of the sensor indicative of movement of the well tool string.

Abstract: A method of mitigating undesired pressure variations in a wellbore due to movement of a well tool string in a well can include selectively decreasing and increasing fluid communication between sections of a wellbore on opposite sides of at least one well tool in the well tool string, the fluid communication being increased in response to detecting a threshold movement of the well tool string relative to the wellbore. A well tool string can include a well tool connected in the well tool string, and having an enlarged outer dimension relative to adjacent sections of the well tool string, a flow passage extending between the well tool's opposite ends, a sensor, and at least one flow control device which selectively permits and prevents fluid communication between the opposite ends via the flow passage, in response to an output of the sensor indicative of movement of the well tool string.

Abstract: A tool insert is removable from a fluid passage in a drill tool body by pressurizing fluid in a removal volume defined between the tool insert and the drill tool body, to by exerting a net fluid pressure bias on the tool insert in a removal direction along the fluid passage. The tool insert can be an annulus sealing assembly mounted in a rotating control device (RCD), with the removal volume being defined radially between a body of the RCD and a bearing assembly of the annulus sealing assembly. A common hydraulic liquid may be used for lubricating the bearing assembly and for hydraulically actuated removal of the annulus sealing assembly.

Abstract: A method of mitigating undesired pressure variations can include flowing fluid between wellbore sections, thereby mitigating a pressure differential due to drill string movement, and the fluid flowing between the wellbore sections via a bypass passage extending through a drilling motor. A drill string can include a drilling motor, a bypass passage in the drilling motor, a sensor, and a flow control device configured to selectively increase and decrease fluid communication between opposite ends of the drilling motor via the bypass passage, in response to an output of the sensor indicative of drill string movement. A method of mitigating undesired pressure variations in a wellbore due to drill string movement can include selectively preventing and permitting fluid communication between wellbore sections on opposite sides of a drilling motor, the fluid communication being permitted in response to detecting a threshold drill string movement.

Abstract: A method and apparatus are disclosed for drilling a wellbore using a concentric dual drill string. Multiple individually selectively isolable crossover ports intervaled may be provided along the length of the drill string thereby facilitating pumping a well control fluid within a wellbore annulus without the need to run-in or trip-out the drill string. Multiple one way check valves may be included at various points within an inner pipe of the dual drill string to minimize settling of particulate matter during long periods of non-circulation. In an offshore arrangement, the drill string may be used without a marine riser. A rotating control device is provided, and a hydraulic power unit is located at the seafloor for controlling and lubricating the rotating control device. A pump may be located at the seafloor for managing wellbore annulus pressure via the rotating control device.

Abstract: A drilling system, rotating control device, and a method for accessing a wellbore may employ a rotating control device arranged to form a dynamic seal between the housing and an exterior of the string to isolate the wellbore annulus under both a positive and a negative differential pressure across the seal. The rotating control device may including a sleeve rotatively disposed within the housing and rotatively carried near a longitudinal midpoint of the sleeve by a thrust bearing assembly. One or more seal retainers may be coupled to and sealed against the sleeve, each including a resilient element disposed to slide to a first sealing position within the seal retainer under a positive differential pressure across the element and to slide to a second sealing position within the seal retainer under a negative differential pressure across the element.

Abstract: A method of maintaining a desired temperature at a location in a well can include adjusting fluid circulation parameters, thereby reducing a difference between an actual temperature at the location and the desired temperature. A well system can include at least one sensor, an output of the sensor being used for determining a temperature at a location in a well, and a hydraulics model which determines a desired change in fluid circulation through the well, in response to the temperature at the location being different from a desired temperature at the location. Another method of maintaining a desired temperature at a location in a well can include adjusting a density, solids content and/or flow rate of a fluid circulated through the well, thereby urging a temperature at the location toward the desired temperature.

Abstract: A tool insert is removable from a fluid passage in a drill tool body by pressurizing fluid in a removal volume defined between the tool insert and the drill tool body, to by exerting a net fluid pressure bias on the tool insert in a removal direction along the fluid passage. The tool insert can be an annulus sealing assembly mounted in a rotating control device (RCD), with the removal volume being defined radially between a body of the RCD and a bearing assembly of the annulus sealing assembly. A common hydraulic liquid may be used for lubricating the bearing assembly and for hydraulically actuated removal of the annulus sealing assembly.

Abstract: A well control method can include removing from a wellbore an undesired influx from a formation into the wellbore, determining a desired pressure profile in real time with a hydraulics model, and automatically operating a flow choking device while removing the undesired influx from the wellbore, thereby influencing an actual pressure profile toward the desired pressure profile. Another well control method can include removing out of a wellbore an undesired influx from a formation into the wellbore, determining a desired wellbore pressure with a hydraulics model, the desired wellbore pressure preventing further influx into the wellbore while removing the undesired influx from the wellbore, and automatically operating a flow choking device while removing the undesired influx from the wellbore, thereby influencing an actual wellbore pressure toward the desired wellbore pressure.

Abstract: A method and apparatus are disclosed for drilling a wellbore using a concentric dual drill string. Multiple individually selectively isolable crossover ports intervaled may be provided along the length of the drill string thereby facilitating pumping a well control fluid within a wellbore annulus without the need to run-in or trip-out the drill string. Multiple one way check valves may be included at various points within an inner pipe of the dual drill string to minimize settling of particulate matter during long periods of non-circulation. In an offshore arrangement, the drill string may be used without a marine riser. A rotating control device is provided, and a hydraulic power unit is located at the seafloor for controlling and lubricating the rotating control device. A pump may be located at the seafloor for managing wellbore annulus pressure via the rotating control device.

Abstract: A rotating control device can include a housing assembly, a body and a clamp device which releasably secures the housing assembly to the body. The clamp device can include a piston which radially displaces a clamp section. A well system can include a rotating control device which includes at least one seal which seals off an annulus between a body of the rotating control device and a tubular string which extends longitudinally through the rotating control device. The rotating control device can also include a piston which displaces longitudinally and selectively clamps and unclamps a housing assembly to the body.

Abstract: A method of maintaining a substantially fixed orientation of a pressure control device relative to a movable rig can include rotating a body of the pressure control device while the rig rotates. A method of remotely controlling an orientation of a pressure control device relative to a movable rig can include rotating a body of the pressure control device, and controlling the rotation of the body from a location on the rig remote from the body. A pressure control device for use in conjunction with a rig can include a body, a flange, an orientation device which changes a rotational orientation of the body relative to the flange, and an orientation control system which remotely controls the orientation device.

Abstract: A method of mitigating undesired pressure variations in a wellbore due to movement of a well tool string in a well can include selectively decreasing and increasing fluid communication between sections of a wellbore on opposite sides of at least one well tool in the well tool string, the fluid communication being increased in response to detecting a threshold movement of the well tool string relative to the wellbore. A well tool string can include a well tool connected in the well tool string, and having an enlarged outer dimension relative to adjacent sections of the well tool string, a flow passage extending between the well tool's opposite ends, a sensor, and at least one flow control device which selectively permits and prevents fluid communication between the opposite ends via the flow passage, in response to an output of the sensor indicative of movement of the well tool string.

Abstract: A method of maintaining a substantially fixed orientation of a pressure control device relative to a movable rig can include rotating a body of the pressure control device while the rig rotates. A method of remotely controlling an orientation of a pressure control device relative to a movable rig can include rotating a body of the pressure control device, and controlling the rotation of the body from a location on the rig remote from the body. A pressure control device for use in conjunction with a rig can include a body, a flange, an orientation device which changes a rotational orientation of the body relative to the flange, and an orientation control system which remotely controls the orientation device.

Abstract: A method of mitigating undesired pressure variations can include flowing fluid between wellbore sections, thereby mitigating a pressure differential due to drill string movement, and the fluid flowing between the wellbore sections via a bypass passage extending through a drilling motor. A drill string can include a drilling motor, a bypass passage in the drilling motor, a sensor, and a flow control device configured to selectively increase and decrease fluid communication between opposite ends of the drilling motor via the bypass passage, in response to an output of the sensor indicative of drill string movement. A method of mitigating undesired pressure variations in a wellbore due to drill string movement can include selectively preventing and permitting fluid communication between wellbore sections on opposite sides of a drilling motor, the fluid communication being permitted in response to detecting a threshold drill string movement.

Abstract: An RCD can include a housing assembly containing a bearing assembly and a rotating seal which seals an annulus between a tubular string and a body of the RCD, and a remotely operable clamp device which selectively permits and prevents displacement of the housing assembly relative to the body. A method of remotely operating a clamp device can include rotating a threaded member which is secured relative to an RCD body, and displacing a clamp section in response to the threaded member rotation, thereby selectively securing and releasing a bearing assembly and an annular seal relative to the body. Another RCD can include a rotating seal which seals an annulus between a tubular string and a body of the RCD, and a remotely operable clamp device which selectively permits and prevents access to an interior of the body, the clamp device including a motor which rotates a threaded member.

Abstract: A method of maintaining a desired temperature at a location in a well can include adjusting fluid circulation parameters, thereby reducing a difference between an actual temperature at the location and the desired temperature. A well system can include at least one sensor, an output of the sensor being used for determining a temperature at a location in a well, and a hydraulics model which determines a desired change in fluid circulation through the well, in response to the temperature at the location being different from a desired temperature at the location. Another method of maintaining a desired temperature at a location in a well can include adjusting a density, solids content and/or flow rate of a fluid circulated through the well, thereby urging a temperature at the location toward the desired temperature.

Abstract: A well drilling method can include transporting a pressure optimization unit to a rig site, the pressure optimization unit including a choke manifold, a control system which automatically controls operation of the choke manifold, and a flowmeter which measures flow of drilling fluid through the choke manifold, and then interconnecting the pressure optimization unit to rig drilling equipment. A pressure optimization unit for use with a well drilling system can include a choke manifold, a control system which automatically controls operation of the choke manifold, and a flowmeter which measures flow of drilling fluid through the choke manifold. The choke manifold, control system and flowmeter may be incorporated into a same conveyance which transports the pressure optimization unit to a rig site.

Abstract: A well drilling method can include transporting a pressure optimization unit to a rig site, the pressure optimization unit including a choke manifold, a control system which automatically controls operation of the choke manifold, and a flowmeter which measures flow of drilling fluid through the choke manifold, and then interconnecting the pressure optimization unit to rig drilling equipment. A pressure optimization unit for use with a well drilling system can include a choke manifold, a control system which automatically controls operation of the choke manifold, and a flowmeter which measures flow of drilling fluid through the choke manifold. The choke manifold, control system and flowmeter may be incorporated into a same conveyance which transports the pressure optimization unit to a rig site.