Multi-bowl wellhead assembly and method of completing a well

This application claims priority to and the benefit of U.S. Provisional Application Ser. No. 61/720,834, filed Oct. 31, 2012 the full disclosure of which is hereby incorporated by reference herein for all purposes.

1. Field of the Disclosure

This invention relates in general to wellheads having bowls for more than one casing hanger, and a method for installing the wellhead assembly.

2. Description of Prior Art

When drilling a well, after drilling to a first depth and installing a conductor pipe, a wellhead can be landed on the conductor pipe. Additional well operations can be performed through this wellhead during the drilling process. During such operations, it may be desirable to temporarily attach certain equipment or components to a top end of the wellhead. At certain times during the drilling process and related operations, it may be necessary or desirable to remove the equipment or components attached to the top of the wellhead. For example, if a easing string becomes stuck and needs to be cut within the wellhead, the equipment or components attached to the top of the wellhead can be removed to facilitate the cutting of the casing. Traditionally, the equipment or components attached to the top of the wellhead are connected to the wellhead with a bolted or threaded connection, making it time consuming to disconnect the equipment or components attached to the top of the wellhead from the wellhead.

After the drilling process and related operations are concluded and the well completion is being finalized, a wellhead member will be secured to the top of the wellhead which is expected to remain in place for the duration of production operations of the well. This more long term wellhead member is traditionally connected to the top of the wellhead with the same connection means as the temporary equipment or components used during drilling operations were attached to the top of the wellhead. However the preferred connection means for connecting the more long term wellhead member to the top of the wellhead may not be ideal for connecting the temporary equipment or components to the top end of the wellhead.

Embodiments of the current disclosure provide a system and method for attaching temporary equipment or components to the wellhead that allows for easy and efficient disconnection, reconnection, or replacement during the drilling process. Embodiments of the current disclosure also allow for a safe and secure connection of a subsequent wellhead member to the wellhead in an alternative manner than what was used to connect the temporary equipment or components to the wellhead. Therefore, a single connection method does not need to be selected for the attachment of both temporary equipment or components and more long term subsequent wellhead members.

In an embodiment of the system and method of the present disclosure, a method of completing a well includes lowering a wellhead onto a base at an upper end of the well. The wellhead has external threads on an enter diameter. A hub with internal threads and an external circumferential stepped recess is secured to the external threads of the wellhead. A blowout preventer with an annular locking member having a plurality of locking elements is landed on the hub and the locking elements are engaged with the recess. The well is drilled through the blowout preventer assembly to a greater depth then the blowout preventer assembly and the hub are removed. A threaded flange with a plurality of bolt holes spaced around the flange is secured to the external threads of the wellhead and a wellhead member is bolted to the bolt holes of the threaded flange.

In certain embodiments, the base comprises a landing ring and before lowering the wellhead onto the base, the landing ring is secured to the upper end of the well. Before lowering the wellhead onto the base, a running loot with internal threads can be secured to the external threads of the wellhead and the wellhead can be lowered onto the base with the miming tool. The wellhead can be lowered through a riser.

In other embodiments, the wellhead can have an upper rim and the blowout preventer assembly can have a blow out preventer and quick connector spool located between the blowout preventer and the annular locking member. In such an embodiment, the quick connector spool is landed on the upper rim of the wellhead. The blow out preventer can be connected to the quick connect spool with bolts before landing the blow out preventer assembly on the hub. Alternatively, the blowout preventer can be bolted to the quick connect spool and the spool can be connected to the annular locking member before landing the blow out preventer assembly on the hub.

In yet other embodiments, an intermediate casing string can be run through the blowout preventer assembly and into the wellhead. If an upper end of the intermediate casing string protrudes above the wellhead when the casing siring can no longer be lowered into the well, the locking elements can be disengaged from the recess and the blowout preventer assembly can be removed. An upper end of the intermediate casing string can be cut within the wellhead and then the blowout preventer assembly can be returned to the hub and the locking elements can be engaged with the recess.

In alternative embodiments of the current disclosure, a method of completing a well includes providing a wellhead with a bore, a rim, and external threads on an outer diameter portion of the wellhead joining the rim. An upper end of a surface casing string is secured to the wellhead, and a running tool is scarred to the external threads. The wellhead is lowered onto a base at an upper end of the well and the surface casing string is cemented. A hub with internal threads and an external circumferential stepped recess is provided and after removal of the running tool the hub is secured to the external threads. A blowout preventer and an annular locking member having a plurality of locking elements are provided and the blowout preventer is bolted to the annular locking member to define a blowout preventer assembly. The blowout preventer assembly is landed on the hub and the locking elements are moved inward into engagement with the recess. The well is drilled through the blowout preventer assembly to a greater depth and at least one inner casing string is cemented in the well. The blowout preventer assembly and the hub are then removed and a threaded flange having bolt holes is secured to the external threads. A tubing head is bolted to the bolt holes of the threaded flange.

In certain embodiments, the wellhead is lowered onto a base with the funning tool through a riser. The riser can be before connecting the hub to the wellhead. The blowout preventer assembly can have a connector spool bolted between the blowout preventer and the annular locking member.

In other embodiments, a connector pipe is extended into the web and a riser is connected to the upper end of the connector pipe with a riser connector. A view port in the riser connector can be opened and it can be visually confirmed that the wellhead has properly landed on the base. Drilling can take place through die riser and the riser can be removed from the upper end of the well before the wellhead is provided. The locking elements can be threaded members that are moved inward into engagement with the recess by rotating the locking elements with a tool.

In another alternative embodiment of this disclosure, a riser is connected to an upper end of a conductor pipe that extends into the well with a riser connector. A wellhead with a support ring at its lower end is provided and lowered through the riser. The wellhead has external threads on an outer diameter. The support ring of the wellhead is landed on a landing ring located at an upper end of the conductor pipe. The riser is then removed. A hub with internal threads and an external circumferential stepped recess is secured to the external threads of the wellhead. A blowout preventer, a connector spool, and an annular locking member having a plurality of locking elements are provided. The blowout preventer is bolted to one end of the connector spool and the annular locking member is connected to an opposite end of the connector spool to define a blowout preventer assembly. The blowout preventer assembly is then landed on the hub, and the locking elements are engaged with the recess. The well is drilled through the blowout preventer assembly to a greater depth then the blowout preventer assembly and the hub are removed. A threaded flange having bolt holes is secured to the external threads of the wellhead and a wellhead member is bolted to the bolt holes of the threaded flange.

In certain embodiments when the support ring of the wellhead is landed on a landing ring, a view port in the riser connector can be opened and it can be visually confirmed that the support ring has properly landed on the landing ring. A running tool with internal threads can be secured to the external threads of the wellhead and the wellhead can be through the riser with the running tool. The running tool can be removed when the riser is removed. An intermediate casing string can be run through the blowout preventer assembly and into the wellhead. If an upper end of the intermediate casing string protrudes above the wellhead when the casing siring can no longer be lowered into the well, the locking elements can be disengaged from the recess and the blowout preventer assembly can be removed. The upper end of the intermediate easing string can be cut within the wellhead and a slips hanger can be installed in the wellhead. The blowout preventer assembly can be returned to the hub and the locking elements can be engaged with the recess.

The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be 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 folly convey its scope to those skilled in the art. Like numbers refer to like elements throughout.

It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.

Referring to, wellhas a larger diameter conductor pipeextending to a first depth. A landing ringis secured or placed on an upper end of conductor pipe. A riserhas a riser connectorthat secures around the upper end of conductor pipe. Risercan have a lower portionat its lower end with an enlarged diameter. Riseris not a subsea riser; rather it is a conduit leading from conductor pipeupward to a drilling fluid diverter (not shown) for conveying returning drilling fluid to equipment for cleaning and recycling.

Riser connectoris a tubular member that is fastened to a lower end of riser, such as by welding. Riser connectorhas radially extending threaded energizing membersspaced around a lower portion. Energizing membersare in engagement with slips or wedgescarried by riser connector. Riser connectoralso has a view portextending through its side wall a short distance below the lower end of riser. A threaded plugselectively closes and seals view port. As riseris lowered onto conductor pipe, a lower part of riser connectorslides over conductor pipe. Threaded energizing membersare then screwed in to energize slipsto grip the exterior of conductor pipe. The operator drills wellthrough riserand conductor pipeto a second depth, with drilling fluid and cuttings returning up riser.

After reaching the second depth, the operator runs a string of surface casingand attaches the upper end of surface casingto a wellhead. Wellheadis a tubular member having a boreand a number of valve portsextending front boreto the exterior of the wellhead. Wellheadhas aspiltsplitsupport ringat its lower end that lands on landing ring. Landing ringacts as a base to support wellhead. When landed, wellheadsits within the lower portionof riser. Support ringand wellheadcan have vertically extending flow by slots to allow for the return flow of cement through the slots and around the wellhead by way of the expanded diameter of lower portionof riserduring cementing. Wellheadhas an upper rimand a set of external threadson its exterior side wall that extend downward from rim.

A running toolhas internal threads that secure to external threads. A running conduit or landing jointsecures to running toolto lower wellheadand surface casingthrough riser. Alter landing wellhead, the operator opens view portto visually determine whether wellheadhas properly landed on landing ring. If properly landed, view portwill be aligned with support ringwhen support ringhas landed on landing ring. Prior to running wellheadinto riser, the operator may apply a circumferential paint strip to support ringthat will align with view portto assist in determining that support ringhas landed on landing ring. After visually confirming support ringhas properly landed on landing ring, the operator closes view portwith plug, then cements surface casing. After cementing surface casing, the operator removes running tooland riser. Optionally, risercan be removed before running wellheadand surface casing. In such an embodiment surface casingand wellheadare not lowered through riser.

Referring to, the operator attaches a hubto external threadson wellhead. Hubis a ring with infernal threads that mate with external threadsand an external circumferential stepped recesson its outer diameter. A quick connector spoollands on rimof wellheadand has an annular locking memberthat skirts hub. Locking memberhas a number of dogs or locking elementsspaced around its circumference. Dogscan be threaded pinsa with inner wedge-shaped engaging elementsb mounted on the inner ends of pinsa. Recessis shown with a single downward facing sloped surface but can alternatively have more than one stepped surface or a series of teeth, forming a circumferential profile that mates with a corresponding profile on engaging elementsb of each dog. Engaging membersb do not rotate, but move inward and enter recesswhen the threaded pinsa are rotated. In such an embodiment, each doghas an outer end with a profile for receiving a fool (not shown) for rotating dogs. Dogsmay alternatively engage recessby other conventional means that will move dogsinward. Locking membermay be secured to quick connector spoolby threadsor other means.

Quick connector spoolhas on its upper end an external flangehaving a number of bolt holesfor receiving bolts to attach quick connector spoolto a blowout preventer (“BOP”). Normally, lock memberwill be secured to quick connector spooland quick connector spoolwill be bolted to BOPprior to lowering the assembly onto wellhead. The assembly of BOP, quick connector spooland lock membercan be quickly attached to hubwith dogs. The operator may also install wing valves,to valve portsat this time.illustrates a different basethanlocated at the upper end of conductor pipe. Baseis typically used if wellheadis run without a riserrather than through riseras shown in.

The operator then drills through BOPand wellheadto a greater depth and runs at least one more-string of casing. In the example of, the operator has drilled to a depth greater bran surface casingand cemented an intermediate casing suing.shows two examples of hanger mechanisms. On the left side, a mandrel hangersecures by threads to the upper end of intermediate casing string. Mandrel hangerlauds on a load shoulderin wellhead. A packoffseals between mandrel hangerand the inner wall of wellhead. As illustrated on the right side of the drawing, a slips type hangermay be employed to grip the exterior of intermediate easing stringin lieu of mandrel hanger. A packoffseals between intermediate easing stringand the interior wall of wellhead.

Slips hangeris more commonly used when the intermediate casing stringbecomes stuck and mandrel hangercannot reach load shoulder. When that occurs, the operator cuts off the upper portion of intermediate casing stringat a selected point within wellhead, then installs slips hanger. In order to cut off intermediate casing string, the operator removes BOPand quick connector spoolby retracting dogs. After cutting the upper portion of the intermediate casing stringand installing slips hanger, the assembly of BOP, quick connector spooland lock memberis re-attached to hubwith dogs. There is no need to undo and remake a threaded connection or to unbolt BOPfrom quick connector spooland re-bolt it, thus saving time to provide access for cutting off intermediate casing stringwhen stuck.

In, after cementing intermediate easing stringand installing packoffor, the operator drills to a final depth and runs a production easing suing. A production casing hangerfor production casing stringis supported on the upper end of the assembly of packoffor. A production casing packoffseals between production casing hangerand wellhead.

As can be seen in, after running casing stringsand, BOPis removed along with quick connector spool, locking memberand hub(). A threaded flangewith internal threads secures to external threadson wellhead. A subsequent wellhead member, such as a tubing headcan then be landed on wellheadand secured to flangewith bolts. A packoffseals between an upper portion of production easing hangerand an inner surface of tubing head. Subsequently, the operator may run a string of production tubing (not shown) through production casing hangerand support the upper end of the tubing string with a tubing hanger in tubing head. As shown in, valveis in communication with the annulus between surface easing stringand intermediate easing string. Valveis in communication with the annulus between intermediate casing stringand production casing string.

As an alternate to the embodiment shown in, the operator may choose to run only a single string of casing. For example, the operator may eliminate intermediate casing stringand just install production casing string. If so, a tubular spacer (not shown) would attach to a lower end of production easing hangerand land in wellhead. The spacer would laud on load shoulderin wellhead housing. Alternately, production easing hangercould land on load shoulderwith the spacer positioned on top of the easing hanger.

The system and method described herein, therefore, are well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the system and method has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the system and method disclosed herein and the scope of the appended claims.