Patent Application
20150204154
The present disclosure generally relates to systems and methods for preparing an oil or gas well. More specifically, the present disclosure relates to systems and methods for attaching and securing a wellhead to the surface casing for use in a drilling or work over operation.
A wellhead assembly includes several components of drilling machinery which must be sealingly attached to a terminal end of the surface casing extending into a drilled well. Due to the vertical height of the fully assembled wellhead, the surface casing is typically terminated at a distance several feet below the surface of the Earth within a constructed cellar. By creating a cellar and terminating the surface casing within the cellar, controls on the highest components of the wellhead assembly are accessible from the surface for operation of the well.
The wellhead attachment to the surface casing must be capable of withstanding pressures of at least 0 to 10,000 psi. Traditionally, this attachment has been achieved by welding the wellhead to a landing mandrel attached to the terminal end of the surface casing within the cellar. This welding task is complex due to the tight quarters of the cellar, the size of the wellhead assembly and the time required to sealingly weld the entire circumference of the landing mandrel. As a result, the current method of connecting the wellhead assembly to the landing mandrel consumes additional labor and resources, and necessitates the use of the drilling rig to support the wellhead assembly in place during welding, rather than freeing the drilling rig for other necessary drilling preparation tasks.
Therefore, a need exists for a cost- and time-effective way to properly and sealingly attach the wellhead assembly to the landing mandrel of the surface casing without monopolizing use of the drilling rig during the valuable well-preparation period.
The present disclosure includes an improved method and device for connecting a wellhead assembly to a surface casing without the requirement of welding or the monopolization of the drilling rig during a lengthy connection process. Included in the base portion of the wellhead assembly is a quick set casing. A landing mandrel is connected to a terminal end of the last joint of the surface casing. The quick set casing includes specifically milled geometry to mate with the landing mandrel. The landing mandrel also includes specifically milled geometry such that, when the quick set casing and the landing mandrel mate, a series of seals and a locking ring are configured to suitably and sealingly connect the quick set casing (and therefore the wellhead assembly) to the landing mandrel (and therefore the surface casing). By using a locking ring comprised of a plurality of locking ring segments, the wellhead assembly need only be lowered onto the landing mandrel, and a sealing connection is achieved by energizing a plurality of radially spaced bolts. The bolts create a sufficient connection when tightened to brace the quick set casing with the bolt and the individual locking ring segments against the landing mandrel on the end of the bolt. By employing the disclosed device and method, connecting the wellhead assembly to the surface casing is significantly simplified resulting in decreased labor, cost, time, and resources required.
Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Invention and the Figures.
Preparing an oil or gas well to access a hydrocarbon formation generally requires the steps of: drilling a hole, installing a conductor pipe in the hole, cementing a surface casing substantially concentrically within the conductor pipe, attaching a wellhead assembly to the surface casing, and completing the drilling process to the required depth of the hydrocarbon formation. One of ordinary skill in the art would understand that the general procedure for drilling and preparing a well can be accomplished in any number of ways.
Regardless of how the well is prepared, all wells require the wellhead assembly to be sealingly attached to a pipe that extends into the ground. Typically, this sealing connection between the wellhead assembly and the pipe is accomplished by means of an extensive circumferential weld between the bottom of the wellhead assembly and the terminal end or connector end of the pipe. In some cases, one or more welds are required to ensure a sealed connection. One of ordinary skill in the art will appreciate that the task of suitably welding the wellhead assembly to the pipe requires a burdensome use of labor, time, money and other resources. In addition to the welding labor and time, the drilling rig must also be occupied during the entire procedure to support the wellhead assembly during the welding process.
Referring now to
Although not illustrated, in most instances, the initial hole is drilled starting at the bottom of a cellar or pit excavated and reinforced from the surface level. In certain embodiments, the cellar is dug to a depth of between two and ten feet. The depth of the cellar largely depends upon the fully assembled height of the wellhead assembly when installed, and is not limited to the two to ten foot range. After installation of the conductor pipe 200, and considering the fully assembled height of the wellhead assembly, the conductor pipe 200 is measured and cut for installation of support ring 202. For purposes of this disclosure, the ring welded onto the end of the conductor pipe is referred to as the support ring, but one of ordinary skill in the art will appreciate that such a well component may be referenced as several different names, including but not limited to starter ring and load ring. The name used herein is exemplary and not limiting. In various embodiments, the attachment of the support ring 202 onto the cut end of the conductor pipe 200 is accomplished prior to moving in the drilling rig (not illustrated) so as to save time and resources.
Following the sizing of the conductor pipe 200 and the attachment of the support ring 202, a diverter system 100 is installed to control flow to the mud pit or mud holding tank while drilling out and cementing the surface casing 301 (See FIGS. 2 and 3). The surface casing 301 is part of a surface casing assembly 300, which includes several components to aid in accurate installation within the conductor pipe 200.
Referring now to
Referring briefly to
In the illustrated embodiment, the landing ring 304 is fluted or includes a lower bevel around its periphery. As illustrated in
It should be appreciated that, by centering the surface casing assembly 300 within the conductor pipe 200, a uniform concrete barrier can be poured between the surface casing 301 and the conductor pipe 200 to ensure safety and fluid tightness in the well. A landing joint 500 is threaded into the top portion of the landing mandrel 400 to accomplish the pumping of concrete into the surface casing 301 and eventually up between the outer circumferential wall of the surface casing 301 and the inner circumferential wall of the conductor pipe 200. It should be appreciated that connecting the various components to one another can occur in any suitable order. Additionally, one of ordinary skill in the art will appreciate that different components can be attached to the surface casing 300 to accomplish the same task of centering the surface casing 300 within the conductor pipe 200 and ensuring an accurate installation of the surface casing 300 in the well.
Referring now to
At this point in the well preparation process, the wellhead assembly (or partial wellhead assembly 600) is prepared for attachment onto the surface casing assembly 300 and conductor pipe 200. It should be appreciated that, although several different wellhead components can be included in a wellhead assembly, only those that directly interact with the connection between the surface casing assembly 300 and the wellhead assembly 600 are discussed in detail herein. Depending upon the type of drilling operation, some or all of the components of the wellhead assembly 600 can be pre-assembled before attachment to the surface casing assembly 300 inside of the cellar.
Referring now to
The quickset casing head 700 is illustrated disassembled from the partial wellhead assembly 600 in
Referring now to
In an assembled configuration of one embodiment, landing mandrel 400 is inserted into the quickset casing head 700. Specifically, when assembled, the groove 402 of the landing mandrel 400 aligns with corresponding groove 706 (see
As discussed above, current methods of attaching a casing head to a landing mandrel require extensive welding in at least one circumferential location. Referring to
Prior to lowering the partial wellhead assembly 600 onto the landing mandrel 400, a segmented locking ring 800 (
As seen in
In the illustrated embodiment, arc angle α=60° and arc angle β=60°. In the embodiment in which arc angle α=60° and arc angle β=60°, it should be appreciated that the spacing of the lockdown bolt holes on the quickset casing head 700 is also 60°. One of ordinary skill in the art would understand that it is necessary to match the lockout hole 804 with the lockdown bolt holes on the quickset casing head 700. Therefore, in various embodiments, the radial displacement of the lockout holes 804 in the segments 802 of the locking ring 800 matches the radial displacement of the lockdown bolt holes in the casing head 700. In one embodiment, the number of equal-sized rings used determines a same arc angle β according to the equation: β°=360°±X, where X=the number of equally sized segments used.
It should also be appreciated that in various un-illustrated embodiments, the arc-shaped ring segments need not be the same size as one another, as in the illustrated embodiment. In such alternative embodiments, arc angles α and β may vary from one ring segment to the next. Similar to evenly-dimensioned ring segments, for varying sized ring segments, the lockdown holes of the quickset casing head will be radially spaced according to the spacing of the lockout holes on the ring segments. In various embodiments, it should also be appreciated that arc angle α is not equal to arc angle β, even if each of the segments includes the same arc angle β. In such embodiments, one of ordinary skill in the art will appreciate that one or more lockout bolts is required to engage a respective lockout hole 804 to retain a single segment 802 within the quickset casing head 700. Similarly, one of ordinary skill in the art would appreciate that some embodiments require the use of more than one lockdown bolt 704 per segment 802.
To install the segmented locking ring 800 into groove 706 of the quickset casing head 700, a lockout bolt (not shown) is first inserted through each of the radially spaced lockdown bolt holes and threaded into the lockout hole 804. The function of the lockout bolt is to draw each segment 802 to the circumferentially outermost wall of groove 706 to provide clearance for the locking mandrel 400 to pass fully into the quickset casing head 700. It should be appreciated that in some embodiments, the lockout bolt is smaller in diameter than the lockdown bolt 704, and is therefore allowed to pass through the lockdown bolt hole without being threaded. In alternative embodiments, the retaining ring 800 is held by a different suitable retaining mechanism than the lockout bolt system described herein.
When the partial wellhead assembly 600 is fully lowered onto the landing mandrel 400 by the drilling rig, the grooves 402 and 706 are aligned, and the segmented locking ring 800 remains retained within groove 706. The seals 702a within grooves 702b of the quickset casing head can provide pressure sealing strength rated from 0 to 10,000 psi. The pressure sealing strength depends upon the seals needed for the job set by the size and working pressure of the well. In various embodiments, the seals are tested for the working pressure of the quickset casing head and the test pressure can be held for at least ten minutes or more. In some embodiments, the seals 702a are tested after the partial wellhead assembly 600 is seated on the landing mandrel 300, but before the quickset casing head 700 secures the partial wellhead assembly 600 to the landing mandrel 300. In various embodiments, the seal test occurs after the secure connection has been made.
The lockout bolts are then removed, and lockdown bolts 704 are threaded through the lockdown bolt holes of the quickset head casing 700. The lockdown bolts thread through the quickset head casing outer wall and into groove 706, and are configured to push radially inwardly against each of the segments 802 of the segmented locking ring 800. As seen in
It should be appreciated that, as seen in
In one present embodiment, the lockout hole 804 of segment 802 is configured to engage a smaller-diameter lockout bolt, but remains too small to engage the larger-diameter lockdown bolt 704. This tolerancing is designed so that a lockdown bolt 704 applies pressure radially inwardly against each entire locking ring segment 802 rather than threading through lockout hole 804 and applying more concentrated pressure from the bolt directly onto the landing mandrel 400. By applying pressure across the larger arcuate surface area of the segment 802 onto the circumference of the landing mandrel 400 in groove 402, the quickset casing head 700 evenly and reliably retains the landing mandrel 400. Alternatively, if lockdown bolts 704 are tightened directly onto the landing mandrel 400 in groove 402 without a locking ring segment 802 to evenly distribute the force across a larger surface area, the connection would result in undesirable concentration of force on the landing mandrel 400 at each lockdown bolt. Such inconsistent force concentration could result in bolts failing before the high pressure capacity required of the connection is achieved.
With the locking system described in the present disclosure, a task that previously required significant labor and several hours is reduced to a task that can be accomplished by one worker energizing the lockdown bolts 704 in less than 30 minutes. In some embodiments, the task can be accomplished by one worker in 22 minutes or less. In addition to enabling a quick and reliable sealed connection between the wellhead assembly 600 and the surface casing assembly 300, the present disclosure allows for quick and easy disconnection of the same. Rather than requiring a torch cutter, saw or other means of removing a welded joint, one must merely unbolt the lockdown bolts 704, insert the lockout bolts to retract the locking ring segments 802 into groove 706, and hoist the wellhead assembly using the drilling rig or winch. It should be appreciated that such ease of maneuverability is desirable to ensure that valves and pipes of the wellhead assembly can be rearranged efficiently as circumstances require by rotating the wellhead assembly. In addition to saving the drilling operator in welding and cutting labor cost, time, and use of the drilling rig for support, the present system also obviates a safety hazard present in previous methods of connection. Due to the relatively small space defined by a typical cellar, the task of welding a wellhead assembly in place onto an installed landing mandrel includes working in cramped quarters increasing the chance for injury, accident or welding error.
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
