WELLHEAD HANGER GRIPPING SYSTEM AND METHOD

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims benefit of U.S. Provisional Patent Application Ser. No. 63/639,099 filed Apr. 26, 2024, which is entirely incorporated herein by reference.

BACKGROUND

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource such as oil or natural gas is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly mounted on a well through which the resource is accessed or extracted. These wellhead assemblies may include a wide variety of components, such as various housings, casings, valves, hangers, pumps, fluid conduits, and the like, that facilitate drilling or production operations.

As will be appreciated, various tubular strings can be run into wells through wellhead assemblies. For instance, wells are often lined with casing that generally serves to stabilize the well and to isolate fluids within the wellbore from certain formations penetrated by the well (e.g., to prevent contamination of freshwater reservoirs). Such casing is frequently cemented into place within the well. During a cement job, cement can be pumped down a casing string in a well, out the bottom of the casing string, and then up the annular space surrounding the casing string. The cement is then allowed to set in the annular space. Wells can also include tubing strings that facilitate flow of fluids through the wells. Hangers can be attached to the casing and tubing strings and received within wellheads to enable these tubular strings to be suspended in the wells from the hangers.

SUMMARY

Certain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.

Certain embodiments of the present disclosure generally relate to the use of a wellhead clamp to elastically deform a wellhead housing to grip a wellhead hanger or other component positioned within the wellhead housing. The wellhead clamp can provide an inward compression force that elastically deforms the wellhead housing into tight, gripping engagement with a wellhead hanger (or other body) received within the wellhead housing. More particularly, some embodiments relate to assessing the grip on the wellhead hanger based on a change in a wall of the wellhead housing elastically deformed by actuation of the wellhead clamp. In some instances, the change in the wall is a change in strain or thickness of the wall. Assessing the grip on the wellhead hanger can include determining a parameter related to the grip, such as a force or pressure applied to the hanger from the grip, or determining in some other manner whether the grip strength is sufficient to securely hold the wellhead hanger within the wellhead housing. A grip strength measuring device is used to assess gripping integrity of the wall of the wellhead housing against the wellhead hanger in some embodiments. Some examples of such a grip strength measuring device include an ultrasonic meter, an acoustic meter, a capacitive sensor, an eddy current sensor, a depth gauge, and a strain gauge.

Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. A gain, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of certain embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 generally depicts various components, including one or more tubular strings and associated hangers, that can be installed at a well in accordance with one embodiment of the present disclosure;

FIG. 2 is a section view of a wellhead assembly having wellhead clamps and strain gauges installed on a wellhead housing in accordance with one embodiment;

FIG. 3 depicts a meter positioned to measure a thickness of a wall of a wellhead housing to assess grip strength of the wellhead housing on a hanger in accordance with one embodiment;

FIG. 4 depicts a depth gauge to measure a depth of a measurement hole in a wall of a wellhead housing to assess grip strength of the wellhead housing on a hanger in accordance with one embodiment;

FIG. 5 depicts a wellhead housing have a measurement core surrounded by a hole formed in an exterior surface of the wellhead housing, and a sensor for measuring movement of an end face of the core to assess grip strength of the wellhead housing on a hanger, in accordance with one embodiment;

FIG. 6 is a front elevational view of the measurement core and hole of FIG. 5 in accordance with one embodiment;

FIG. 7 is similar to FIG. 5 and depicts a wellhead housing having multiple measurement cores, holes, and sensors in accordance with one embodiment;

FIG. 8 depicts a wellhead housing having measurement cores and holes at three measurement locations along a wellhead housing in accordance with one embodiment;

FIG. 9 is a graph depicting a measured distance between a sensor and an end face of the measurement core at a first measurement location of FIG. 8 over time in accordance with one embodiment;

FIG. 10 is a graph depicting a measured distance between a sensor and an end face of the measurement core at a second measurement location of FIG. 8 over time in accordance with one embodiment;

FIG. 11 is a graph depicting a measured distance between a sensor and an end face of the measurement core at a third measurement location of FIG. 8 over time in accordance with one embodiment;

FIG. 12 depicts a wellhead housing having measurement cores and holes at two measurement locations along a wellhead housing in accordance with one embodiment;

FIG. 13 is a detail view showing a portion of the wellhead housing having the two measurement locations of FIG. 12 in accordance with one embodiment;

FIG. 14 is a detail view showing a measurement core and hole of one measurement location of FIG. 13 in accordance with one embodiment;

FIG. 15 is a perspective view of a portion of the wellhead housing of FIG. 12 with the addition of connectors and a cover in accordance with one embodiment;

FIG. 16 is an exploded view of the wellhead housing portion of FIG. 15 in accordance with one embodiment;

FIG. 17 depicts a wellhead housing having a hole in its external surface for receiving a visual grip strength indicator in accordance with one embodiment;

FIG. 18 depicts the wellhead housing of FIG. 17 with a visual grip strength indicator mounted to the wellhead housing via the hole in accordance with one embodiment; and

FIG. 19 depicts the wellhead housing of FIG. 18 with a cap of the visual grip strength indicator squeezed against the external surface of the wellhead housing following elastic deformation of the wellhead housing in accordance with one embodiment.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Specific embodiments of the present disclosure are described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, any use of “top,” “bottom,” “above,” “below,” other directional terms, and variations of these terms is made for convenience, but does not require any particular orientation of the components.

Turning now to the present figures, a system 10 is illustrated in FIG. 1 in accordance with one embodiment. Notably, the system 10 is a production system that facilitates extraction of a resource, such as oil, from a reservoir 12 through a well 14, such as an onshore well. Wellhead equipment 16 is installed on the well 14. As depicted, the wellhead equipment 16 includes a wellhead housing 20 and wellhead hangers 22. The wellhead housing 20 may include one or more casing heads and a tubing head in some instances. In some cases, the wellhead housing 20 includes a single-piece body designed to receive multiple hangers 22, such as a casing hanger and a tubing hanger. The hangers 22 can be mandrel-style hangers or slip-style hangers. The components of the wellhead equipment 16 can differ between applications, and could include a variety of casing heads, tubing heads, spools, housings, hangers, sealing assemblies, stuffing boxes, pumping tees, and pressure gauges, to name only a few possibilities.

The wellhead hangers 22 can be positioned on landing shoulders 24 within hollow wellhead bodies (e.g., within the wellhead housing 20). These landing shoulders 24 can be integral parts of the wellhead housing 20 or can be provided by other components, such as sealing assemblies or landing rings disposed in the wellhead housing 20. In some instances, a wellhead hanger 22 can be secured within a hollow wellhead body using a gripping device without landing the wellhead hanger 22 on a landing shoulder 24. In such an embodiment, landing shoulders 24 may be omitted from the wellhead housing 20. Each of the hangers 22 can be connected to a tubular string, such as a tubing string 26 or a casing string 28, to suspend the string within the well 14. The well 14 can include a single casing string 28 or include multiple casing strings 28 of different diameters. Casing strings 28 are often cemented in place within the well.

By way of further example, a wellhead assembly 40 is depicted in FIG. 2 as having a hollow wellhead housing 20 with an axial bore 42 extending from a lower end 44 of the housing 20 to an upper end 46. The wellhead assembly 40 of FIG. 2 includes gripping devices 50, which may also be referred to as wellhead clamps 50, positioned to elastically deform the wellhead housing 20 to securely grip wellhead hangers within the bore 42. The depicted wellhead clamps 50 each include a compression ring with compression segments 52, a lower energizing ring 54, and an upper energizing ring 56. These components can have any suitable form. In some embodiments, the compression ring is a segmented annular ring formed of four compression segments 52 arranged circumferentially about the wellhead housing 20, although some other number of compression segments 52 could be used. Separation of adjacent segments 52 facilitates contraction of the compression ring about the wellhead housing 20. The compression ring could be provided as an annular ring with one split in its circumference (i.e., a C-ring) in other instances.

Through the tapered engagement of the compression segments 52 with the energizing rings 54 and 56, drawing the energizing rings 54 and 56 toward one another applies a radially inward compression force to the compression ring segments 52, which contract and elastically deform the wellhead housing 20 to grip a wellhead hanger positioned along the bore 42 inside the clamp 50. Although a wellhead hanger is not depicted inside the clamp 50 in FIG. 2, such a wellhead hanger could be installed and gripped inside the clamp 50 at some other time. The energizing rings 54 and 56 can be connected to one another in any suitable manner, such as with studs 60 and nuts 62. It will be appreciated that the clamp 50 can include any suitable number of studs 60 and nuts 62, such as twelve or sixteen pairs of circumferentially arrayed studs 60 and nuts 62. In some instances, the energizing rings 54 and 56 include tool recesses 64 (e.g., annular grooves) to facilitate use of a tool, such as a hydraulic tool, for drawing the rings 54 and 56 together to actuate the clamp 50.

The compression ring segments 52 may be positioned in recessed portions 68 of the outer surface of the wellhead housing 20 to facilitate elastic deformation of the wellhead housing 20 when the clamps 50 are actuated. As shown in FIG. 2, one clamp 50 is positioned near the top of the wellhead housing 20 to elastically deform the wellhead housing 20 and grip a hanger of a tubular string, such as a tubing string, while another clamp 50 is positioned lower along the wellhead housing 20 to elastically deform the wellhead housing 20 and grip a hanger of another tubular string, such as a casing string. But in other embodiments, the wellhead housing 20 may have more or fewer clamps 50, such as a single clamp 50 for elastically deforming the wellhead housing 20 to grip a single hanger within the bore 42.

To facilitate installation of a wellhead hanger, when the clamp 50 is in a relaxed state and is not elastically deforming the wellhead housing 20, the diameter of the bore 42 can be sufficiently greater than the outer diameter of the wellhead hanger to allow free movement of the wellhead hanger within the bore 42 to its desired position. The wellhead hanger can be lowered into the wellhead housing 20 and moved to this desired position, after which the clamp 50 can be energized to compress the wellhead housing 20 radially inward to elastically deform the wellhead housing 20 and cause the inside wall of the wellhead housing 20 to contact and grip the wellhead hanger. In some instances, the wellhead hanger includes teeth on its external surface to bite against the inside wall of the wellhead housing 20 and facilitate gripping of the hanger by the housing 20. The extent of actuation of the clamp 50 can be adjusted to vary the gripping force of the wellhead housing 20 on the hanger.

As noted above, some embodiments of the present disclosure facilitate assessment of the integrity of the gripping of a wellhead housing, such as the housing 20, to a wellhead hanger. This gripping can be used to carry the weight of the hanger (and attached equipment, such as a tubular string) and to resist any vertical forces, either downward due to weight or upward due to well pressure. Various examples for sensing the integrity of this gripping are provided herein. At least some embodiments include a sensing technique that does not introduce any new leak paths to a wellhead assembly or any other modifications that would compromise sealing or safety of such assemblies. The presently described sensing systems can be used to provide feedback on gripping integrity during installation of a wellhead hanger. In some instances, such systems may also or instead be used to monitor gripping in situ following installation (e.g., periodically, continually, or continuously monitoring gripping during installation or throughout the lifetime of the wellhead). In at least some embodiments, assessing the grip of the wellhead housing on a wellhead hanger includes detecting a change in a wall of the wellhead housing elastically deformed through actuation of a wellhead clamp.

By way of example, in some instances assessing grip of a wellhead housing on a wellhead hanger includes measuring strain following actuation of the wellhead clamp. In FIG. 2, the wellhead assembly 40 is depicted as having strain gauges 72 and 74 to measure strain on the wellhead housing 20. The strain gauges 72 may be positioned on an exterior surface of the wellhead housing 20, while the strain gauges 74 may be positioned on an interior surface of the wellhead housing 20. Although two strain gauges 72 and two strain gauges 74 are depicted in FIG. 2, it will be appreciated that the wellhead assembly 40 could include any suitable number of strain gauges, which could be more or fewer than four strain gauges depicted in FIG. 2. Indeed, in some embodiments the wellhead assembly 40 will not include strain gauges, and grip on the wellhead hanger may be assessed in some other manner. Further, when present, a strain gauge may also or instead be positioned on some other component of the wellhead assembly 40, besides the wellhead housing 20, to measure strain and facilitate grip assessment. For instance, as shown in at least FIGS. 3-5, a strain gauge 76 may be positioned on a wellhead hanger 80 positioned within the wellhead housing 20 to measure strain on the wellhead hanger 80 (e.g., from gripping by the wellhead housing 20). But other sensing systems to assess grip strength are also shown in FIGS. 3-5 and in other figures, and it will be appreciated that the strain gauge 76 may be omitted, used in place of, or used in addition to such other sensing systems described elsewhere herein. When present, a strain gauge 72, 74, or 76 can be positioned at any suitable location, such as radially inward of a clamp 50, or above or below the clamp 50.

In some other embodiments, detecting a change in a wall of the wellhead housing elastically deformed through actuation of a wellhead clamp includes detecting a change in a thickness of the wall of the wellhead housing. More specifically, in certain embodiments a compression force from the wellhead housing 20 on a wellhead hanger (e.g., on wellhead hanger 80), and thus the vertical load carrying capacity, is assessed by measuring a thickness change of the wellhead housing 20 at or near the hanger position as a result of the wellhead wall being compressed radially inward by the external clamp 50. When the inside wall of the wellhead housing 20 contacts the outside wall of the hanger 80 during actuation of the clamp 50, the hanger 80 starts to exert radially outward resistance forces. As the wall of the wellhead housing 20 is squeezed between the hanger 80 and the clamp 50, the radial thickness of the wall located directly between, and compressed by, the hanger 80 and the clamp 50 decreases; this thickness change may be proportional to the squeeze force, which in turn may be proportional to the vertical load carrying capacity of the hanger-wellhead housing interface.

The outward force that the hanger 80 transfers to the wellhead housing 20 and the deformation it imparts on the housing 20 can therefore be indirectly measured by measuring the wellhead wall thickness. A wellhead wall thickness measurement location along a portion of the wall located directly between the hanger 80 and the clamp 50 may give the greatest thickness change, but an axial location along the wellhead housing 20 above or below the clamp 50 may be more accessible in practice. For example, the apparatus depicted in FIG. 3 includes a meter 82 is used to measure wall thickness of the wellhead housing 20 at an axial location above the hanger 80 and clamp 50. The meter 82 can take any suitable form, such as an ultrasonic meter or acoustic meter. The meter 82 is positioned to measure thickness of the wall between an outer surface 84 and inner surface 86 of the wellhead housing 20. A signal 88 (e.g., an ultrasonic or acoustic sound pulse) may be transmitted by the meter 82 into the wall from the outer surface 84, at least a portion of which is reflected by the inner surface 86 back to the meter 82. The travel time for the signal transmitted through the wall and reflected back to the meter 82 is used to calculate the thickness of the wall. The meter 82 could be used to measure thickness of the wall multiple times to detect deformation of the wellhead housing by actuation of the clamp 50. For instance, a series of thickness measurements could be taken during actuation of the clamp 50 to detect changes in the wall thickness during actuation.

In another embodiment generally depicted in FIG. 4, the wellhead housing 20 includes a measurement hole 92, which may be a hole drilled into the outer surface 84 of the housing 20. As illustrated, the hole 92 does not extend into the bore 42 and has a hole bottom 94 located in the wall of the housing 20. When the housing 20 gets squeezed during actuation of the clamp 50 the wall thickness may decrease, which causes the depth of hole 92 (from the outer surface 84 to the hole bottom 94) to decrease. Although a depth gauge 96 having a rod 98 is generally depicted in FIG. 4, the depth of the hole 92 can be measured in any other suitable manner. In at least some instances, depth measurements are taken at multiple times during installation to see the wall thickness change.

In some embodiments, changes in thickness of a wall of the wellhead housing 20 are identified by detecting relative displacement of a surface of the wellhead housing. In FIGS. 5 and 6, for instance, a wall of the wellhead housing 20 includes a measurement hole 102 formed in the outer surface 84. The hole 102 has a bottom 104 and does not penetrate to the bore 42. The hole 102 surrounds a measurement core 106 such that an end face 108 of the core 106 is separated, by the hole 102, from the portion of the outer surface 84 surrounding the hole 102. The hole 102 can be provided in any suitable shape but is shown as an annular hole 102 encircling and defining the core 106 in FIG. 6. Further, the hole 102 can be formed in any suitable manner. In some instances, the hole 102 can be formed via electrical discharge machining, with a core bit, or in some other way that leaves the core 106 as an integral portion of the wall of the wellhead housing 20 (i.e., the core 106 is material of the wall remaining within the hole 102 following formation of the hole 102). In at least such instances, certain physical properties of the core 106 (e.g., thermal expansion and elasticity properties) can be the same as the material of the surrounding wall of the wellhead housing 20. In some other instances, the core 106 in the wall of the wellhead housing 20 may be an insert positioned within the hole 102, such as an insert threaded into a tapped hole at the bottom 104 of the hole 102 or an insert welded into place within the hole 102.

Measuring the amount by which the core face 108 deflects (e.g., radially moves) with respect to the outer surface 84 surrounding the hole 102 (e.g., the core face 108 protruding beyond the outer surface 84 surrounding the hole 102 or retracting into the hole 102) gives an indication of the change in wall thickness when the wall of the housing 20 is elastically deformed via the clamp 50. This measurement can be taken in any appropriate fashion. For instance, this measurement could be taken manually using a depth gauge or could be taken using a sensor 110 (e.g., a capacitive sensor, an eddy current sensor, or any other suitable sensor) positioned radially outward of the end face 108. In at least some embodiments, the hole 102 is formed in a flat housing face of the outer surface 84 (i.e., the core face 108 and the portion of the outer surface 84 surrounding the hole 102 are flat surfaces) to facilitate measurement.

Although a single hole 102 and core 106 are depicted in FIG. 5, it will be appreciated that multiple holes 102 and cores 106 may be arranged about the wellhead housing 20 to allow measurement at various locations. In FIG. 7, for example, two holes 102 and cores 106 are shown at locations axially above the clamp 50, two holes 102 and cores 106 are shown at locations axially below the clamp 50, and an additional hole 102 and core 106 are shown in a location axially aligned with and radially inward of the clamp 50. Holes 102 and cores 106 may also or instead be arranged at other circumferential locations about the housing 20

Another example of a wellhead housing 20 having measurement holes 102, cores 106, and sensors 110 for assessing gripping integrity of the housing 20 on a hanger 80 is shown in FIG. 8. In this embodiment, the holes 102, cores 106, and sensors 110 are depicted in three locations along the housing 20. Moving from top to bottom in FIG. 8, these locations are a first location above the clamp 50, a second location above the clamp 50 (between the first location and the upper end of the clamp 50), and a third location radially inward of the clamp 50. The sensors 110 (e.g., a capacitive sensor or some other suitable sensor) are positioned to detect relative movement of the cores 106 when the wellhead housing 20 is elastically deformed via the clamp 50, such as described above. As will be appreciated, the separation provided by the holes 102 cause the end faces of the cores 106 to move toward or away from the bore 42 by different amounts than the outer surface of the wellhead housing 20 surrounding the holes 102 when the housing 20 is deformed via the clamp 50.

Examples of distances measured from the sensors 110 in FIG. 8 to the end faces of the cores 106 over time during actuation of the clamp 50 are generally depicted in FIGS. 9-11. More particularly, FIG. 9 represents distance measured by the uppermost sensor 110 in FIG. 8, FIG. 10 represents distance measured by the next sensor 110 (below the uppermost sensor 110 and above the clamp 50) in FIG. 8, and FIG. 11 represents distance measured by the lowermost sensor 110 in FIG. 8. The graphical depictions of FIGS. 9-11 are provided by way of example. It will be appreciated that distance measured can vary between locations and between different embodiments (e.g., based on the physical characteristics and geometries of different embodiments), and that the shapes of the graphical depictions of the sensor response may vary from those shown in FIGS. 9-11. Each of FIGS. 9-11 depicts measured distance changing over a time period in which the clamp 50 moves from a relaxed state to an energized state in which the clamp 50 has elastically deformed the wellhead housing 20 into gripping engagement with the hanger 80. In the present example of FIGS. 9-11, the clamp 50 is actuated to provide a linear compression force to the wellhead housing 20 over time. While the time scale is identical among FIGS. 9-11, the distance scales are not identical in this example. In some instances, the magnitude of the change in distance measured in FIG. 9 from the starting time to the ending time (from the relaxed state to the energized state) is 3.0-3.5 microns, the magnitude of the change in distance measured in FIG. 10 from the starting time to the ending time is 8-9 microns, and the magnitude of the difference between the minimum and maximum distance recorded in FIG. 11 is 6-7 microns. In FIGS. 9 and 10, the measured distance is shown generally increasing over time during actuation of the clamp 50. In contrast, in FIG. 11 the measured distance (by the lowermost sensor 110 in FIG. 8) begins to rise as the clamp 50 is actuated but reaches a maximum and begins to fall while the clamp 50 continues to be actuated and while the distances measured by the other sensors 110 of FIG. 8 continue to rise. This difference in behavior at the lowermost core 106 may be due to resistance of the hanger 80 to the compression of the housing 20 by the clamp 50.

In some embodiments, assessing the grip on the hanger 80 by the elastically deformed housing 20 includes comparing the distance measured by a sensor 110 (or multiple sensors 110) to one or more thresholds. For instance, in certain embodiments distance measured by a sensor 110 (e.g., the lowermost sensor 110 of FIG. 8) can be compared to either or both of an upper threshold and a lower threshold. As represented in FIG. 11, by way of example, an upper threshold 112 can be a minimum desired distance change 114 (from a starting distance 116) during actuation of the clamp 50, and a lower threshold 118 can be a maximum desired ending distance change 120 (from the starting distance 116) after actuation of the clamp 50 has finished and the hanger 80 is set within the housing 20. In this example, the grip on the hanger 80 can be considered sufficient if the magnitude of the maximum distance change 122 exceeds the minimum desired distance change 114 (e.g., the distance measured exceeds the upper threshold 112) during actuation of the clamp 50 and if the ending distance measured after actuation of the clamp 50 deviates from the starting distance 116 by less than the magnitude of the difference between the starting distance 116 and the lower threshold 118 (e.g., the ending distance is below the lower threshold 118). Any suitable thresholds may be used. In some cases, the upper threshold 112 will be 3-15 microns (at any point in this inclusive range) from the starting distance 116, while the lower threshold 118 will be less than the upper threshold 112 and will be 1-5 microns (at any point in this inclusive range that is below the upper threshold 112) from the starting distance 116. In some other embodiments, the grip may be determined to be sufficient by comparison to a single threshold, such as the measured distance passing a threshold 112 at some point during actuation of the clamp 50 or the measured distance passing a threshold 118 in opposite directions (e.g., starting below the threshold, then exceeding the threshold, and then falling below the threshold during actuation). Grip can be determined to be insufficient if the measured distance does not meet the threshold expectations, such as if the measured distance does not rise to the upper threshold 112 or return to a distance below the lower threshold 118.

Still another example of a wellhead housing 20 having measurement holes 102, cores 106, and sensors for assessing gripping integrity of the housing 20 on a hanger 80 is shown in FIGS. 12-16. As best shown in FIG. 13, this embodiment includes two measurement locations having holes 102 and cores 106 along the housing 20: a first measurement location located above the clamp 50 and a second measurement location radially inward of the clamp 50. Sensors may be used to detect relative movement of the cores 106 and measure distances between the sensors and the cores 106, such as described above. The housing 20 can include recesses 132 (FIGS. 14 and 16) for receiving such sensors near the cores 106. As also depicted in FIGS. 14 and 16, the housing 20 can include one or more slots 134 to facilitate communication between a sensor installed in a recess 132 that is radially inward of the clamp 50 and a location axially offset from the clamp 50.

The apparatus can also include connectors 136 and a cover 138, as shown in FIGS. 15 and 16. The connectors 136 facilitate communication with an external controller or monitoring system, such as a processor-based system with memory and stored instructions that can be executed by a processor to perform various functionality described herein, such as receiving measurement signals, assessing grip integrity (e.g., by comparing measured values to one or more thresholds), and providing output (e.g., measurements or grip assessments) to a user. Although the connectors 136 are depicted with sockets for receiving cable plugs, in other instances connectors 136 may be configured in some other manner, such as for wireless communication with an external system. The connectors 136 and cover 138 may also protect internal components of the sensing system.

In the embodiment depicted in FIG. 16, the sensing system includes an upper assembly 140 for the upper measurement location along housing 20 and a lower assembly 142 for the lower measurement location along housing 20. The upper assembly 140 includes a connector 136, a circuit board 144, a spacer 146 (e.g., an O-ring), and a sensor 148 that may be installed in the recess 132 of the upper measurement location. The lower assembly 142 includes a connector 136, the cover 138, a circuit board 152, a spring 154, a spacer 146 (e.g., an O-ring), and a sensor 148 that may be installed in a recess 132 of the lower measurement location. The sensors 148 may be capacitive sensors or any other suitable sensors, and in some instances may be identical to sensors 110. The spacers 146 may help seat the sensors 148 within the recesses 132. Although one spring 154 is depicted in FIG. 16, one or more springs 154 may be used in either or both the upper assembly 140 and the lower assembly 142 to bias other components to desired positions (e.g., to maintain seating of the sensor 148 within the recess 132).

The circuit boards 144 and 152 can be provided in any suitable form but are printed circuit boards in at least one embodiment. The depicted circuit boards 144 and 152 enable electrical communication between the sensors 148 and external devices via the connectors 136. In FIG. 16, the circuit board 152 has an elongated shape configured to be received in a slot 134 and to generally allow communication to travel axially between the sensor 148 of the lower assembly 142 and the connector 136 of the lower assembly 142. In other instances, a communication cable may also or instead be used in the slot 134 to communicate between the sensor 148 and the connector 136. The cover 138 can be a shield used to reduce interference on the communication path between the sensor 148 and the connector 136 of the lower assembly 142 in some instances.

As noted above, a sensor (e.g., sensor 110 or 148) may be used to measure a distance to an end face 108 of a core 106 of the wellhead housing 20 at a measurement location. This may be better understood with reference to FIG. 14, which generally depicts a sensor 148 installed in a recess 132 at a measurement location. The sensor 148 may be seated in the recess so as to provide a gap 150 between the end face 108 and the sensor 148. The width of this gap 150 and the measured distance to the end face 108 changes as the wellhead housing 20 is elastically deformed by the clamp 50 to grip the hanger 80. In some cases, the width of the gap 150 is 40-70 microns before actuation of the clamp 50.

Various embodiments described herein include measuring a parameter (e.g., strain, thickness, depth, or distance) that changes in response to deformation of a wall of the wellhead housing 20 by the clamp 50. In addition to radial deformation of the wellhead housing through actuation of the clamp 50, the compressed wellhead wall may also experience axial deformation generally perpendicular to the radial deformation due to the Poisson effect. In certain instances, the Poisson effect may cause a wall of the wellhead housing at a measurement location (e.g., a location above or below the clamp 50) to increase in thickness rather than decrease in thickness. The strain, thickness, depth, distance, or other parameter measured to assess grip of the wellhead housing 20 on a hanger 80 (or on some other component within the bore 42) can be compared to one or more threshold levels that may be above or below a starting value of that parameter before elastic deformation of the wellhead housing 20. These one or more threshold levels can be determined through prior modeling, testing, or in any other suitable manner. For instance, a given threshold level can be set, based on prior testing, at a level for which the parameter to be measured would be deemed sufficient to indicate at least a minimum desired grip strength by the elastically deformed wellhead housing 20 on the hanger 80, and assessing the grip strength includes determining whether the measured parameter has reached the desired threshold level.

In some embodiments, the wellhead housing 20 may also or instead include a visual indicator to facilitate assessment of the grip of the housing 20 on a hanger 80. One such embodiment is depicted in FIGS. 17-19, in which the housing 20 includes a measurement hole 162 formed in the outer surface 84 above the clamp 50. The depicted hole 162 has a threaded portion near a bottom 164 of the hole 162. This threaded portion of the hole 162 may have a narrower diameter than the portion of the hole 162 closer to the outer surface 84. A cap screw 170 having a threaded end 174 and head 176 may be screwed into the hole 162 when the housing 20 is not under stress (e.g., when the housing 20 is not being elastically deformed by the clamp 50), such as shown in FIG. 18. A cap 172 is retained on the cap screw 170 by the head 176. The cap 172 can include a tool access port 178 to allow a tool (e.g., a screwdriver) to thread the cap screw 170 into or out of the hole 162.

As depicted in FIG. 18, the cap screw 170 and cap 172 are configured such that the cap 172 is free to rotate about the head 176 when the wellhead housing 20 is not being elastically deformed by the clamp 50. In this example, the hole 162 is at a location in the wall of the wellhead housing 20 at which the wall thickness increases (due to the Poisson effect) as the clamp 50 is actuated to elastically deform the housing 20. As the clamp 50 is actuated, the thickness of the wall of the wellhead housing 20 at the hole 162 increases, causing a tensile strain force on the cap screw 170 and an end of the cap 172 to be squeezed between the head 176 of the cap screw 170 and the outer surface 84 of the housing 20, such as shown in FIG. 19. In this state, the cap 172 is held tightly and is no longer free to rotate about the head 176. The dimensions of the cap screw 170 and cap 172 may be selected to allow free rotation of the cap 172 until the clamp 50 is actuated and the grip of the elastically deformed housing 20 on the hanger 80 is sufficiently strong to provide a desired load carrying capacity. Once the cap 172 cannot be rotated, it is an indication that the wellhead wall thickness has increased to a desired value, which is an indirect indication that the hanger 80 has been adequately gripped. In this manner, an operator may determine whether the grip of the housing 20 on the hanger 80 is sufficiently strong based on the state of the cap 172 (freely rotatable or fixedly held).

While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.