Patent Application
20120152561
1. Field of the Invention
The present invention relates to riser management systems. More particularly, the present invention relates to a system, program product, and related methods for controlling a well during an emergency.
2. Description of Related Art
A problem presented by offshore hydrocarbon drilling and producing operations conducted from a floating platform or vessel is the need to establish a sealed fluid pathway between each borehole or well at the ocean floor and the work deck of the vessel at the ocean surface. This sealed fluid pathway is typically provided by a drilling riser system. Drilling risers, which are utilized for offshore drilling, extend from the drilling rig to a blowout preventer (BOP) which is directly or indirectly connected to an upper portion of a subsea wellhead. A typical marine drilling riser permits passage of drill pipe which is used for pumping lubricating mud down the well during drilling operations, return of drilling mud that has been pumped through the drill pipe into the main tube of the riser, and any associated drill cuttings, and provides a connection of the drilling vessel to the well above the subsea BOP stack. Similarly, production risers extend from and provide communication between the subsea wellhead system and the floating vessel.
The BOP, often referred to as a BOP stack, is a specialized valve or set of valves used to control and monitor the subsea well. The BOP stack generally includes two categories of blowout preventers: ram and annular. The ram-type BOP typically uses a pair of opposing steel rams which can extend radially to either block or open a fluid passageway extending through the BOP stack. The ram BOP includes pipe rams, blind rams, shear rams, and blind sheer rams. Pipe rams close, around the pipe to restrict flow in the annulus between the outside of the drill pipe and inner bore of the BOP stack when a drilling pipe is extending, through the bore of the BOP stack. Blind rams, which have no openings for tubing, close off the bore completely when no drilling pipes extend through the BOP stack by pressing against each other to form a seal. Shear rams and blind shear rams cut through the drilling pipe with hardened steel shears. The annular BOP functions similar to a sphincter,
The different preventers can have different closure diameters to accommodate for either the existence of drilling pipe or different diameters of drilling pipe. The BOP stack also includes a number of choke and kill lines that extend alongside the riser and enter the interior of BOP at different points between BOP elements which can be used to shut down the subsea well.
The drilling riser can be disconnected from the well above the 130P stack, allowing the drilling vessel to retrieve the riser and temporary move from the drill site should the need arise (i.e., during a hurricane event, or a malfunction). Having remained atop the wellhead, when functioning properly the BOP stack provides for containment of a live well while the vessel is not on location. Upon return, the vessel can deploy the riser, reconnect to the BOP stack, and reestablish hydrocarbon communication with the well,
The marine drilling riser also permits control of the well during an emergency through use of the BOP stack, Emergencies requiring activation of components of the BOP stack are typically associated with drilling through a zone with geological fluid pressure that is substantially higher than that which the drilling mud can contain. During such events, one or more of the different types of preventer of the BOP stack is hydraulically functioned to close off or restrict the flow of well fluid flowing through the BOP stack. Well control is then re-established by pumping an appropriate density mud through the kill line and eventually circulating it back to the surface via the choke line.
Recent newsworthy events, however, have highlighted that BOPs can have reliability issues. In a recent event, failure of the BOP to activate resulted in destruction of the drilling, rig and substantial environmental damage due to the failure of the BOP stack to stop well fluid flow into the surrounding ocean. Accordingly, recognized by the inventors is that there needs to be a two fault system in place and a wellhead based emergency control apparatus can advantageously provide the necessary fault protection by providing an independent, safe guard system. Also recognized by the inventors is that currently existing well control systems do not provide for a. wellhead based method for shutting, off a well. Recognized by the inventors, therefore, is the need for a wellhead-based systems, apparatus, and methods of controlling the flow of well fluid in an emergency that is independent of the BOP. Specifically, recognized by the inventors is the need for systems, apparatus, and methods which can include an emergency well fluid shutoff assembly positioned separately from the BOP stack which can radially compress casing strings and/or drilling pipe extending through the subsea wellhead without shearing in order to obtain a substantial reduction in the flow of well fluid through the subsea wellhead. Also recognized by the inventors is the need for systems, apparatus, and methods which include an emergency well fluid diversion assembly to divert well fluid from within the wellhead housing to an external conduit to thereby release fluid pressure of well fluid flowing within the wellhead housing in a. controlled manner.
In view of the foregoing, various embodiments of the present invention advantageously provide systems, apparatus, and methods of controlling the flow of well fluid in an emergency that is independent of the BOP. Various embodiments of the present invention include systems, apparatus, and methods which can include an emergency well fluid shutoff assembly positioned separately from the BOP stack which can radially compress casing strings and/or drilling pipe extending through the subsea wellhead without shearing in order to obtain a substantial reduction in the flow of well fluid through the subsea wellhead. Various embodiments of the present invention also include systems, apparatus, and methods Which include an emergency well fluid diversion assembly to divert well fluid from within the wellhead housing to an external conduit to thereby release fluid pressure of well fluid flowing within the wellhead housing in a controlled manner
Specifically, an embodiment of the present invention provides a wellhead-based control apparatus to control a well. The apparatus can include an emergency well fluid shutoff assembly connected to or integral with a wellhead housing. The emergency well shutoff assembly can include a casing strings compression assembly positioned to radially compress each of it plurality of casing, strings extending, through a bore of the wellhead housing, and a casing strings compression actuator operably coupled to the casing strings compression assembly to actuate the casing strings compression assembly. According to an exemplary embodiment of the present invention, the casing strings compression assembly includes a pair of opposing compression rams positioned to extend radially toward a center of the bore of the wellhead housing to apply a compressing force at a same coaxial location to each of the plurality of casing strings.
Each of the pair of opposing compression rams can include a hydraulic piston connected to a portion of the wellhead housing to apply the compressing force. As such, the casing strings compression actuator can include a hydraulic source including various components such as, for example, a hydraulic accumulator storing pressurized hydraulic fluid, a hydraulic pump assembly having a hydraulic pump, a motor positioned, to drive the hydraulic pump, and a hydraulic fluid reservoir. Alternatively, each of the pair of opposing compression rams can include a linear actuator connected to a portion of the wellhead housing that when rotated extends casing string engagement surfaces of the compression rams toward a center of the bore of the wellhead housing to apply the compressing force to the plurality of casing strings. As such, the casing strings compression actuator can include one or more electric motors positioned to rotate the linear actuators and an electrical power source. A remote activation controller operably connected to or integral with the emergency well fluid shutoff assembly is configured to receive remote activation commands and to provide a remote activation signal to the casing strings compression actuator to cause actuation of the casing strings compression assembly.
According to an exemplary embodiment of the present invention, the wellhead based control apparatus separately or additionally includes an emergency well fluid diversion assembly connected to or integral with the wellhead housing. The emergency well fluid diversion assembly can include a casing strings penetrator positioned to form an aperture in each of the plurality of casing strings at approximately a same coaxial location, and a well fluid diverter positioned to extend through the apertures in each of the casing strings to divert well fluid from within the wellhead housing to an external conduit to thereby release fluid pressure of well fluid flowing within the wellhead housing in a controlled manner.
The penetrator can be implemented according to various means such as, for example, in the form of a cutting blade assembly positioned to cut an aperture through the wellhead housing and the plurality of casing strings, an electrical discharge cutting assembly positioned to cut an aperture through the wellhead housing and the plurality of casing strings, a chemical milling assembly positioned to cut an aperture through the wellhead housing and the plurality of casing strings, an explosive discharge cutting assembly including a explosive charge operably connected to a cutting torpedo to cut an aperture through the wellhead housing and the plurality of Casing strings, just to name a few.
In an exemplary configuration, the diverter includes a maw body, a passageway extending through portions of the main body along a main axis thereof to channel well fluid from within the wellhead housing, and a well fluid collection aperture extending through at least a portion of the diverter and connecting to the passageway to provide a fluid channel to the passageway. The well fluid collection aperture of the diverter can be in the form of a downward facing recess that does not extend through the main body of the diverter so that when the diverter is operably positioned and sealed within the wellhead housing, the well fluid collection aperture channels well fluid into the passageway in the main body to divert well fluid from within the wellhead housing to an external conduit. Correspondingly, outer surface portions of the diverter can be shaped and material-wise configured to extend through and engage inner surface portions of an aperture in the wellhead housing to form a fluid-tight seal. Also or alternatively, inner surface portions of one or more of the apertures extending through the casing strings can be sized to form a sealing relationship with the outer surface portions of the diverter and the inner surface portions of the one or more of the apertures. A remote activation controller operably connected to or integral with the emergency well fluid diversion assembly is configured to receive remote activation commands and to provide a remote activation signal to the casing strings penetrator to cause the formation of the aperture in each of the plurality of casing strings, and/or the well fluid diverter to extend through the aperture in each of the plurality of casing strings to divert well fluid from within the wellhead housing to an external conduit.
Embodiments of the present invention also include methods to control a well. For example, a method according to an embodiment of the present invention can include employing a casing strings compression assembly of an emergency well fluid shutoff assembly to radially compress each of the plurality of casing strings extending through portions of the wellhead to restrict well fluid passage. The method can also include employing a casing strings penetrator of an emergency well fluid diversion assembly to form an aperture in at least one of a plurality of casing strings and extending a well fluid diverter through an aperture in a side of the wellhead housing and one or more of the apertures cut by the penetrator to divert well fluid from within the wellhead housing to an external conduit. According to an exemplary embodiment of the method, insertion of the diverter can be accomplished by initially inserting portions of the diverter with the upper and lower surfaces of the inserted portions of the diverter oriented at least partially transverse to a direction of flow of well fluid within the wellhead housing to thereby allow well fluid to bypass the diverter, and rotating the diverter to orient the downward facing aperture in a direction of the well fluid, within the wellhead housing to divert well fluid from within the wellhead housing to the passageway in the diverter and to an external conduit. The step of rotating the diverter can include first sealingly engaging outer surface portions of the diverter with inner surfiice portions of the aperture in at least one of the plurality of casing strings, and orienting the downward facing aperture in a direction of the well fluid within the wellhead housing to divert well fluid from within the wellhead housing to the passageway in the diverter and to an external conduit,
Various embodiments of the present invention advantageously provide a wellhead based well control apparatus attached to or integral with a wellhead system to control the well. The well control apparatus can advantageously include both an emergency well fluid shutoff assembly and an emergency well fluid diversion assembly. The emergency well fluid shutoff assembly can be actuated to stop or restrict the flow of oil and gas from a subsea well whereby the stoppage or restriction can be accomplished by compression of the casing strings, such as 22″, 13⅝″ and for 10¾″ casings, so that little or no flow area remains. The restriction can be provided, by mechanically collapsing the well casing, strings, for example, by mechanically applied forces or explosively applied forces. Collapsing forces can be achieved through piston style rams driven by pressure, driven by electro-mechanical motors, phase change material systems, or by direct high pressure as from an explosive apparatus. Other means of collapsing the casing are nevertheless within the scope of the present invention. The emergency well fluid diversion assembly can be actuated to penetrate the wellhead housing and/or casing and/or drilling string in order to control the flow of oil and gas from the subsea well Advantageously, a penetrator can be employed to penetrate the well by drilling or by perforation through the casing strings so that the flowing string can be restricted or diverted. A diverter, separate from or integral with the penetrator, can act to create a new flow path emanating from one or more of the penetrated well casings. The penetration of the wellbore may be performed by various means such as, for example, boring, chemical milling, electrical discharge machining, or via perforation using explosive charges. Once the bore is penetrated, a physical barrier forming a diverter can be introduced through the penetration to divert the flow from the wellbore. Advantageously, the diverter, connected to or integral with the penetrator can advantageously have a bore for conducting the flow of fluids once the penetrator/diverter is in place. Advantageously, the apparatus can also include a control system or systems to control both portions of the well fluid shutoff assembly and portions of the well fluid diversion assembly that, as a minimum, can be actuated remotely, independent of platform control system or personnel, such that the control system or systems is isolated from known failure modes such as a riser failure or well blow out/rig destruction event.
So that the manner in which the features and advantages of the invention, as well as others which will become apparent, may be understood in more detail, a more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it may include other effective embodiments as well.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, which illustrate embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Referring to
As shown in more detail in
According to an exemplary embodiment of the present invention, each of the pair of opposing compression rams 74, 75, can include a hydraulic or electric piston 77 connected to a portion of the wellhead housing 41 to apply the compressing force. As such, when implemented hydraulically, the casing strings compression actuator 73 can include a hydraulic source including various components such as, for example, a hydraulic accumulator storing pressurized hydraulic fluid, a hydraulic pump assembly having a hydraulic pump, a motor positioned to drive the hydraulic pump, and a hydraulic fluid reservoir as known and understood by one of ordinary skill in the art. Alternatively, piston 77 can be in the form of a linear actuator connected to a portion of the wellhead housing 41 that when rotated extends casing, string engagement surfaces of the compression rams 74, 75, toward a center of the bore 43 of the wellhead housing 41 to apply the compressing force to the casing strings 45, 47, 49. As such, when implemented electrically, the casing strings compression actuator 73 can include one or more electric motors positioned to rotate the linear actuators and an electrical power source as known and understood by one of ordinary skill in the art. A remote activation controller 79 operably connected to or integral with the emergency well fluid shutoff assembly 61 is configured to receive remote activation commands and to provide a remote activation signal to the casing strings compression actuator 73 to cause actuation of the casing strings compression assembly 71.
As shown in more detail in
The penetrator 91 can be implemented according to various means as known understood by one of ordinary skill in the art such as, for example, in the form of a cutting blade assembly 99 (see, e.g.,
Referring to
Embodiments of the present invention also include methods to control a well 31. For example, referring to
Embodiments of the present invention provide several advantages. In the case of a subsea blowout, the only means of well control is currently the subsea blow out preventor (BOP). If the closure mechanisms of the BOP fail to work, there is not another means to stop or control the flow from the subsea well. This could result in the catastrophic and uncontrollable spillage of reservoir products into the ocean. The subsea wellhead emergency shut off/diversion apparatus 30 according to an embodiment of the present invention is a separate mechanism from the BOP that is capable of either shutting off or severely restricting the flow from a subsea blowout, or for diverting the flow of the well. The apparatus 30 may be run as part of the subsea wellhead, or run after the wellhead is installed, as with existing wells. Operation of the apparatus 30 can be performed, for example, through one of several means: (1) Utilization of an external system, such as an ROV, to actuate the shut off device by either torque, linear actuation, or pressure supplied by the ROV. This closure can pinch, shear, or penetrate any casing strings landed in the high pressure housing or wellhead system. The external system would generally supply the needed power and communications link to the apparatus 30. The ROV may engage the wellhead BOP device directly or from some distance from the well 31. (2) An in-situ system, integral to the shut-off device, can be utilized to actuate the shut off apparatus 30 to perform either torque, linear actuation, or other operations to effect well control. The in-situ system can supply the needed power and communications link, either wired or wireless, to the apparatus 30. Energy sources can include among others, mechanical, chemical, (e.g. batteries & explosives), or compressed fluids. (3) The activation of the apparatus 30 can be independent of the primary BOP control system or platform personnel. The activation system can, however, be activated by any of the above means (dual or multiple activation capable). The activation of the apparatus 30 can be, at a minimum, operable from a remote platform, control ship, or land based operation that is independent of the platform from which the drilling operations are being conducted,
In the drawings and specification, there have been disclosed a typical preferred embodiment of the invention, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The invention has been described in considerable detail with specific reference to these illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the invention as described in the foregoing specification.
