Cap for a hydrocarbon production well and method of use

A cap for a hydrocarbon production well, the cap having a body with a top and a bottom. The bottom having a first connecting flange with a first seal face. The first connecting flange configured to connect to an end flange of a wellhead component and the top having a second connecting flange with a second seal face.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 371 of the filing date of International Patent Application No. PCT/EP2017/079025, having an international filing date of Nov. 13, 2017, which claims priority to Great Britain Application No. 1619855.8, filed Nov. 24, 2016, the contents of both of which are incorporated herein by reference in their entirety.

The present invention relates to a cap for use with a hydrocarbon production well, for example a cap for use on a wellhead or a valve tree.

BACKGROUND

The present disclosure relates to methods and equipment for petroleum exploration and exploitation. Prior art useful to give a general understanding of the field of technology includes CN 104989314 A, U.S. Pat. Nos. 5,107,931, 7,654,329 and US 2013/306325. U.S. Pat. No. 7,600,571 describes a method and apparatus for re-entering an abandoned well having a production plate arranged to seal a production casing.

In petroleum production, there is commonly a need to temporarily abandon a well, i.e. shut down and stop production from the well for a certain period of time. This period can be anything from a few days, to months or even several years. As opposed to a permanent abandonment of the well, where the wellhead is removed and the casings cut below the mudline, the operator will have an option of re-entering the well at a future time. In a temporary abandonment, permanent measures, such as removing the well casing and wellhead, will therefore not be carried out.

Such temporary abandonment is commonly carried out by setting cement plugs downhole, and arranging a temporary abandonment cap and/or a valve arrangement on the wellhead or the valve tree (Xmas/Christmas tree). One can thereby re-enter the well, for example in order to repair if leaks should occur.

It is of great importance that such temporary abandonment equipment and methods provide a safe and reliable solution, for example to minimize the risk of leakage from the well. Moreover, it is desirable that temporary abandonment can be carried out in a low-cost and effective manner, with low maintenance needs.

In other instances, there may be a need to enter the well and/or gain access to a valve tree independently of a temporary abandonment, for example in case some or all of the actuated valves have failed in a producing well.

The present invention has the objective to provide equipment and methods to meet at least one of the above mentioned requirements, while providing improvements and/or alternatives to known solutions and techniques.

SUMMARY

In an embodiment, there is provided a cap for a hydrocarbon production well, said cap having a body with a top and a bottom, the bottom having a first connecting flange with a first seal face, the first connecting flange configured to connect to an end flange of a wellhead component, the top having a second connecting flange with a second seal face.

The cap may further comprise a packing seal arranged on the first connecting flange.

The cap may further comprise a recess extending from said first connecting flange into said body.

The cap may further comprise a channel extending between an outside of the cap and the recess.

The cap may further comprise a sensor device arranged in fluid communication with the channel.

The cap may further comprise a cover arranged on the second connecting flange, the cover arranged to cover the second seal face.

The cover may comprise at least one packing seal arranged in sealing engagement with the second connecting flange.

The first connecting flange, the second connecting flange and the body may be machined from a single piece of metal material.

In an embodiment, there is provided a wellhead component having a cap, the wellhead component being a valve tree or a wellhead.

In an embodiment, there is provided a method for entering a hydrocarbon production well, comprising the steps:

providing a wellhead component having a cap according to any of the embodiments described above, the wellhead component being a valve tree or a wellhead,

connecting a riser to the second connecting flange of said cap in sealing engagement with the second seal face,

lowering a machining tool into the riser and machining a through-going opening through the body of said cap.

In an embodiment, the well has a downhole plug, and the method comprises the further step of removing or replacing said downhole plug.

In an embodiment, the method further comprises the step of placing a downhole plug in the well.

In an embodiment, the method further comprises the step of machining through at least one valve in the valve tree.

In an embodiment, the step of machining an opening through the body comprises at least one of the steps: milling an opening through the body, and drilling an opening through the body.

In an embodiment, the method further comprises the step of machining through a sensor device and/or a component for a sensor device connected to the body.

In an embodiment, there is provided a method for enabling re-entry into a hydrocarbon production well, comprising the steps: providing a cap according to any of the embodiments described above, and arranging the cap on a wellhead component of the well.

In an embodiment, the method further comprises the step of plugging the well by setting at least one plug in the well.

In an embodiment, the wellhead component is a valve tree, or the wellhead component is a wellhead.

DETAILED DESCRIPTION

In an embodiment, there is provided a cap100for a hydrocarbon production well.FIG. 1illustrates schematically a well700extending from a subterranean reservoir701to a wellhead200in the conventional manner. A valve tree300(commonly known as a Xmas tree) is arranged on the wellhead200. The cap100may be arranged on a top flange of the valve tree. Alternatively, the cap100may be arranged on the wellhead200. These alternatives will be described in further detail below. The well700illustrated inFIG. 1has a surface wellhead200, however the disclosure herein is not limited to any particular type of well and the wellhead may equally well be, for example, a subsea wellhead. In certain embodiments, the well700may have downhole plugs702,703arranged therein, or such plugs may be placed into the well700. This will be described in further detail below.

The cap100is illustrated in further detail inFIGS. 2A-D. The cap100has a top100aand a bottom100b. The bottom100bof the cap100has a first connecting flange101with an annular first seal face102which encloses a surface area A of the cap100at the bottom100b, in this embodiment a circular area A, having a size which is substantially similar to or slightly larger than the cross-sectional area of the top of the wellhead bore with which the cap100is intended to be used. The top100aof the cap100has a second connecting flange103with an annular second seal face104which encloses a surface area B of the cap100at the top100a. The body105is arranged/plugged such that no fluid communication is possible between the area A enclosed by the first seal face102and the area B enclosed by the second seal face104.

The seal faces102and104are parts of the flanges101and103and are prepared, machined and/or treated such as to provide sufficient sealing properties against packing seals108and602(see e.g.FIG. 5B), for example in relation to their surface roughness properties and geometry.

The first flange101is configured to connect to an upper end flange201,301of a wellhead component. The wellhead component may be the wellhead200itself (seeFIG. 3A), a valve tree300(seeFIG. 4A), also known as a Christmas tree, or any other intermediate component arranged with the wellhead200and having a through bore in communication with the well. When connected, the area A will overlap at least partly with a through bore202of the wellhead200or, alternatively, with a through bore of the valve tree300.

The cap100in this embodiment comprises a recess106with a bottom having the aforementioned area A. The recess106extends into the body105from the bottom100bof the cap100. A channel107extends from the recess106to an outside of the cap100. The channel107may extend to the outside of the cap100through the side of the cap100, as shown inFIG. 1, or through the body105and via the top100a, as shown in e.g.FIGS. 5A and 6A. Alternatively, more than one channel may extend to the outside of the cap100, as shown inFIGS. 6A and 6B.

A sensor device400, for example a pressure sensor, may be arranged in the channel107or in fluid communication with the channel107. In this embodiment, a pressure gauge base401is arranged in the channel107with a pressure gauge402optionally connectable to the base401. The pressure gauge base401blocks the channel107to prevent any fluid flowing through it, and allows the pressure gauge402to be connected for monitoring of the pressure in the recess106.

A cap cover500can be arranged on the second connecting flange103and arranged to cover or protect the second seal face104. The cap cover500may be arranged to seal against the second connecting flange103by means of one or more packing seals501a-f(see alsoFIGS. 5A and 6A). The cap cover500may, for example, be made from Teflon™, nylon, or a similar material.

The cap100, including the first connecting flange101, the second connecting flange103and the body105may be machined from a single piece of metal material. This improves structural strength and reduces the risk of leakage etc.

Examples of the use of a cap100according to the above described embodiment will now be outlined.

When a well is to be temporarily abandoned, the well will be prepared according to how long the well is intended to remain abandoned. If the well is to be abandoned for longer periods of time, the valve tree300and parts or all of the completion equipment (production tubing, non-cemented casings, etc.) are usually removed. The wellhead200is, however, not removed. The well is plugged downhole with e.g. cement plugs702,703, schematically indicated inFIG. 1, arranged in the wellbore. This will prevent reservoir fluids from flowing to surface. Conventionally, a temporary abandonment cap is arranged on the wellhead in order to provide an additional barrier, and in order to monitor the pressure at the wellhead, and the temporary abandonment cap may have a valve to enable reentry into the well for repairs or further plugging (e.g. for permanent abandonment) of the well at a later time, if required.

According to one embodiment, when the well has been plugged, a cap100according to one of the designs described herein may be placed on the upper flange of the wellhead200.FIG. 3Aillustrates a cap100arranged on the upper flange201of a wellhead200. An annular metal-to-metal packing seal108(seeFIG. 1) is arranged to seal between the upper flange201and the first flange101of the cap100. Clamp connectors109a,bare used to secure the connection.

When in place, the cap100will seal the outlet of the through bore202of the wellhead200(or the outlet of the valve tree300, as the case may be). The shown cap100comprises no reentry valve and very few seal faces, and therefore provides a safe and reliable seal for the well which may remain in place for long periods of time with little or no maintenance. If a sensor device400is used, such as a pressure sensor, one can monitor the state inside the through bore202and thus identify for example potential leakage past the downhole plugs and consequent pressure build-up at the wellhead.

The cap cover500, if used, will protect the top of the second connecting flange103, including the seal face104. The space between the cap cover500and the second connecting flange103may be grease-filled. Regular maintenance of the temporarily abandoned well may include temporarily removing the cap cover500and replacing the grease, to ensure reliable protection of the seal face104in order to avoid e.g. corrosion or damage. The cap cover500may have a snap connection or the like for this purpose. Optionally, this may include replacing the cap cover500itself at regular intervals. The cap cover500may be “top-hat”-shaped to cover a gauge base401located on the top100a, as illustrated inFIG. 6A.

When re-entry into the well is required, such as for permanent plugging, a riser600can be connected to the second flange103and brought in sealing engagement with the second seal face104. The riser600may comprise a blowout preventer stack601(seeFIG. 3B) and/or other relevant pressure control equipment for this operation.FIGS. 5B, 5C, 6B and 6Cshow further details of the connection between the riser600and the cap100. A metal-to-metal packing seal602may be provided between the seal face104and a corresponding seal face of the lower flange603of the riser600. Clamp connectors605can, for example, be used to secure the connection. When connected, the area B at the top100aof the cap100is accessible from the internal bore604of the riser600.

After pressure testing of the connections, milling equipment800(seeFIG. 6B) is run into the riser600to mill out an opening in the body105of the cap100, to create a connection between the riser bore604and the through bore202of the wellhead200. When the milling is finished, the well can be intervened through the riser600and the opening in the cap100, and further operations can be carried out, such as replacement of downhole plugs and other operations necessary for permanent plugging or repairs.

The method according to this embodiment may include the further step of removing the riser600, attaching a production riser (not shown) and commencing production from the well. Alternatively, the method may include the step of setting additional plugs in the well700for plugging the well. Such plugs may be cement plugs for permanent abandonment and plugging of the well700.

The machining tool may be a milling tool, a drilling tool, or any equivalent tool capable of machining an opening in the cap100.

If a sensor device400, or any component associated therewith, such as the base401, is arranged at the top100aof the cap100, the machining tool800may also machine through this device.FIGS. 5A-Cshow an example of this case.FIG. 5Aillustrates the situation during the temporary abandonment, with the cap100in place with the cap cover500attached. In order to re-enter the well, the cap cover500is removed, and a riser600connected to the second connecting flange103. This situation is shown inFIG. 5B.FIG. 5Cshows the situation after milling, where part of the body105and the sensor device400have been machined out.FIGS. 6A-Cshow the same steps for a system in which the pressure gauge402has been removed.

According to some embodiments, the need for a valve in the temporarily abandoned wellhead to enable re-entry is therefore eliminated, since a system and/or method according to embodiments described herein permit such re-entry when required. This saves the cost of the valve and the maintenance required to service it regularly (e.g. every year) until the well is re-entered, or the hydrocarbon production platform is finally decommissioned and torn down, and the well permanently plugged. If required, providing a connection channel107on the cap100will enable pressure monitoring during the years of waiting on final decommissioning.

FIGS. 4A and 4Billustrate a situation where the cap100is arranged on a valve tree300. The valve tree300has a plurality of valves310a-eand is arranged on a wellhead200in the conventional manner. If access is required from above to the vertical through bore of the valve tree300, access through the cap100may be obtained in the equivalent manner as described above.FIG. 4Billustrates this, with a riser600having a blowout preventer stack601being connected to the second flange103of the cap100, and the machining of an opening through the cap100can begin.

The cap100can thus, for example, be installed on a valve (Christmas) tree300as a contingency device to gain access to the tree in case some or all actuated valves have failed. In this case, the method may also include machining through at least one valve310a-clocated in the through bore of the valve tree300. When the machining is finished and access is gained from the riser600, through the wellhead through bore202and into the well700, the well can be intervened and secured using e.g. bridge plugs and/or back pressure valves.

The cap100can be installed on the valve tree as a permanent feature when the tree is installed or retrofitted as part of normal wellhead maintenance. The cap100can, for example, be used in cases where some or all valves310a-ehas failed, and where it is not possible to rig up well services equipment on the well. In such a case, the embodiments described herein may provide an alternative to, for example, performing a freezing operation or to kill the well. In mature fields, such a kill operation can be an undesirable option as the fluid level in the well cannot be appropriately monitored. A freeze option can be both complicated and not risk-free.

The present invention is not limited to the embodiments described herein. Reference should be had to the appended claims.