Saver filling sub

Abstract

A tubular sub (14) for use between a drilling machine's (12) tubular drive shaft (121) and a work string (17), alternatively between a drive shaft extension (121b) coupled to the drilling machine's (12) tubular drive shaft (121), and the work string (17) in a hydrocarbon-related well (2), a thermal-related well (2) or a water-related well (2), wherein the sub (14) acts both as a saver sub to protect a threaded portion (121a) on the drilling machine's (12) tubular drive shaft (121) or a threaded portion (121c) on the drive shaft extension (121b), and as a filling tool for filling the work string (17) with a liquid when the work string is being run in the well (2), characterized in that an internal tubular lower centre passage portion (144) extending from an internal tubular upper centre passage portion (143) and towards an outlet opening (144a) of the sub (14), deviates from a shape with a constant internal diameter to provide a controlled shape of a liquid jet when the liquid is flowing freely from the outlet opening (144a) of the sub (14).

Description

[0001] SAVER FILLING SUB

[0002] The invention concerns a so-called saver filling sub, i.e. a crossover unit for use between a drive unit’s (kelly / top drive) tubular drive shaft and a work string in a hydrocarbon-related well, a thermal-related well or a water-related well, wherein the saver filling sub, herein also called (the) sub, acts both as a saver sub for protecting the threads on the pipe shaft of the drilling machine, potentially on a drive shaft extension, and as a filling tool for filling the work string when the work string is being run in the well.

[0003] A so-called saver sub for a drilling machine’s tubular drive shaft is a short, tubular unit provided with a threaded portion at each end. It is screwed tight onto the outwardly projecting end of the drive shaft. When it is necessary to extend the wellbore and add further pipes to the work string (the drill string), the work string is disconnected from the sub while the coupling between the sub and the drive shaft is left untouched. This means that the coupling between the drive shaft and the sub is rarely used and therefore suffers minimal wear and tear, while the lower threaded portion of the sub is used in almost all cases and suffers the most wear and tear. The sub may be considered a consumable component and does not represent a major cost, while the coupling components of the drive unit suffer minimal wear and tear. These components represent a significant capital cost and considerable downtime when they need replacing.

[0004] To reduce the risk of damage to the drilling machine's tubular drive shaft as well as reduce the need for and / or simplify the replacement of the saver sub, it is often preferred to dispose an additional sub as a direct extension of the drilling machine’s saver sub. This additional sub is of a tubular shape and of a length that provides better access for tools (e.g. tongs) used in make-up and opening of pipe joints in the work string. To a person skilled in the art it is evident that this additional sub may be an assembly made up of several subs screwed together to make up an extension of a preferred length.

[0005] When running a work string, which may be a drill string, a casing string, a completion string, an intervention string and a general workover string, in wells, it is often necessary to fill the work string while the work string is hung off, for example in the drive unit via e.g. a collar-type elevator. When the work string is hanging in a collar-type elevator, there is a distance between the upper end of the work string and the saver sub, and this often leads to spillage on the outside of the work string when the work string is being filled with liquid due to said distance and the spread of the liquid jet out from the saver sub. By hanging off the work string in a slips in or near a drilling deck while the work string is being extended, the distance between the upper end of the work string and the saver sub may be reduced while the work string is being filled. However, this is a time-consuming, repetitive and not very desirable operation.

[0006] In recent times there have been several types of tools that are mounted in the drive unit to enable filling the work string with liquid without needing to hang off the work string in slips to reduce the distance between the saver sub and the work string and thereby avoid liquid spilling on the outside of the work string. The common denominator for all pipe filling tools of today is that they must be installed and uninstalled for the different types of work strings they are used on. This means more time spent, increased cost, more handling of equipment with an associated increased security risk, and halted run-in of the work string in the wellbore, which entails a risk of the string getting stuck if there is open formation exposed in the well.

[0007] When running a tool string in a well, usually at run-in, it is often necessary to fill the work string to avoid the work string collapsing or floating when it is being run into the well, since the bottom of the work string usually is closed so that liquid does not flow into the work string from the well.

[0008] There may also be other reasons why it would be desirable to fill the work string as it enters the well, for example for controlling volume, reducing the need for time-consuming filling in the event it becomes urgently necessary to circle down the work string with return to the surface, limiting the pressure difference on a non-return valve at the bottom of the work string or other conditions that require the work string to be filled as it is being run into the well.

[0009] Today, mainly top drive drilling machines are used in well drilling and workover, wherein a saver sub is used on the end of the drilling machine’s tubular drive shaft to protect the drive shaft’s threaded portion against wear and damage. Filling of a work string is usually done by placing a saver sub that is screwed onto the drilling machine’s pipe shaft, directly above the upper end of the work string to avoid spillage outside the work string and to vent air when filling the work string.

[0010] Halting the run-in to fill the work string is not optimal, as it takes more time and increases the risk of the work string getting stuck when at standstill in case the work string is exposed towards an open and challenging formation.

[0011] Several types of filling tools and circulation tools exist that are installed on the drilling machine’s saver sub before running in the work string. This mainly applies to running of casing strings where, by using this type of tool, the casing string may be filled at the same time as it is being run into the well. There are advantages and disadvantages to using filling tools and circulation tools to fill the casing string during run-in. The advantages are the time savings achieved by not needing to halt the run-in to fill the casing string, as well as avoiding spillage outside the casing string during filling. The disadvantage is that this is an additional tool that is installed in the drilling machine’s saver sub before run-in of the casing string is started. This takes time and also constitutes an additional handling of tools with an associated increased security risk. When the casing string has been run and before it is to be landed in a wellhead, the tool must be dismounted from the drilling machine’s saver sub. This takes time, and large parts of the casing string are exposed to open formation, and a halt can cause problems for further running of the casing string on a so-called landing string in a subsea wellhead solution or subsequent landing in the wellhead for a fixed rig or land rig. Circulation tools and filling tools are mainly hired equipment carrying significant cost and logistics requirements.

[0012] From US 3869150 A is known a saver sub having threaded ends and being designed to be able to be coupled to a so-called Kelly joint in a drill string. A lower end is designed with a millout to provide a circumferential surface to which a tubular element may be fastened. The tubular element is further arranged so that it runs axially downwards and past a shoulder. The tubular element is adapted to fit over a drill pipe end. During use, when the Kelly joint and the saver sub have been pulled out and separated from the drill pipe end, drilling mud in the Kelly joint will disappear out through an annular space. By the drilling mud hitting an internal deflection surface in the tubular element, the drilling mud will be deflected and guided down through openings in a rotary table and further down in one or more flow nipples arranged below the rotary table so as to join a drilling mud flow that is being returned to the drilling mud reservoir of the drilling rig. NO 345136 B1 references a method for supplying liquid from a liquid supply to a casing string which from an installation is guided down into a well by means of a pipe handling device comprising an elevator, wherein the liquid is supplied through an upper casing that is added to the casing string, as well as an apparatus for transferring a liquid fluid from a supply to a receiving pipe in the form of a casing string.

[0013] US 7975766 B2 describes a device for top-filling of pipes, such as pipes used in drilling operations. In an embodiment, a nozzle device is adapted for joining with a male coupling of a top drive. An elongated spout of a relatively small diameter extends beyond the threaded portion of the nozzle device and is arranged to be insertable through the pipe neck and into the pipe bore to fill the pipe. In an alternative embodiment, the nozzle device is provided with a nozzle insert which, when fluid is pumped through the nozzle device at great speed, forms a well-defined liquid jet. When the nozzle device is placed just above and at a distance from the upper end of the pipe string, the formed fluid jet passes through the pipe neck.

[0014] The purpose of the invention is to remedy or reduce at least one of the disadvantages of prior art, or at least provide a useful alternative to prior art.

[0015] The purpose is fulfilled by the features specified in the description below and the subsequent patent claims.

[0016] The present invention provides a sub acting both as a saver sub to protect the threads on the drilling machine’s tubular drive shaft, alternatively on a drive shaft extension, and a filling tool for filling the work string at the same time as the work string is being run in a well. The unit is therefore also referred to as “saver filling sub” herein. It must also be understood that the saver filling sub, in the case that one or more drive shaft extensions are used, will make up the lower part of the assembly, so that the saver filling sub leads out directly above the work string when the work string is being run in the well, and may be coupled to I screwed into the upper part of the work string. The drive shaft extension may in some embodiments be made up of a standard saver sub according to prior art.

[0017] The invention contributes to time and cost savings in that it is not necessary to install additional tools for filling the different work strings, as well as improved HSSE due to less equipment handling and reduced logistics requirements.

[0018] The invention is defined by the independent patent claim. The dependent claims define advantageous embodiments of the invention. According to a first aspect, the invention concerns a tubular sub for use between a drilling machine’s tubular drive shaft and a work string, alternatively between a drive shaft extension coupled to the drilling machine’s tubular drive shaft, and the work string in a hydro- carbon-related well, a thermal-related well or a water-related well, wherein the sub acts both as a saver sub to protect a threaded portion on the drilling machine’s tubular drive shaft or a threaded portion on the drive shaft extension, and as a filling tool for filling the work string with a liquid when the work string is being run in the well, characterised in that an internal tubular lower centre passage portion extending from an internal tubular upper centre passage portion and towards an outlet opening of the sub, deviates from a shape with a constant internal diameter, to provide a controlled shape of a liquid jet when the liquid is flowing freely from the outlet opening of the sub.

[0019] The internal tubular lower centre passage portion of the sub may be formed convergently towards the outlet opening. An advantage of this embodiment is that the liquid jet may be concentrated towards an inlet opening of the work string.

[0020] At least one of the internal tubular upper centre passage portion and the internal tubular lower centre passage portion of the sub may be provided with longitudinal ridges distributed on the circumference of the internal tubular upper centre passage portion and the internal tubular lower centre passage portion respectively. An advantage of this embodiment is that the control over the shape of the liquid jet flowing from the sub is further improved.

[0021] The internal tubular lower centre passage portion of the sub may be convergent between the internal tubular upper centre passage portion and an outlet portion that diverges towards the outlet opening. Alternatively, the outlet portion may be cylindrical. An advantage of these embodiments is that the shape of the liquid jet flowing from the sub may be adapted to alternative dimensions of the inlet opening of the work string.

[0022] In an embodiment, the internal tubular lower centre passage portion may be formed of an interchangeable insert. An advantage of this embodiment is that the sub may easily be adapted to the work string that is to be handled.

[0023] The sub may be designed with different combinations of thread types for upper and lower end portions as well as different combinations of internal and external threads on upper and lower end portions of the sub. It is advantageous if the internal wall surface of at least the internal tubular lower centre passage portion of the sub is polished smooth so as to contribute to a more collected liquid jet when liquid is flowing freely from the sub.

[0024] In an embodiment, the sub may also act as a slip ring sub, which may typically be the case if the work string is a wired drill pipe string. The sub may then be used to transfer electrical communication between the drill pipe string and stationary equipment topside. Alternatively, the filling saver sub may be a so-called wired sub, which is coupled to the lower part of a slip ring sub, wherein the slip ring sub then constitutes a drive shaft extension or at least a portion of a drive shaft extension.

[0025] In another embodiment, the sub may act as a crossover (crossover joint / casing swage) between pipe strings of different dimensions. In that case, the lower part of the sub will be adapted to the work string (typically casing or drill pipe).

[0026] According to a second aspect, the invention concerns a drilling system comprising an annular sub according to the first aspect of the invention, wherein the drilling system further comprises:

[0027] - a drilling machine with a drive shaft; and

[0028] - a work string, wherein the annular sub is coupled between the drive shaft, potentially a drive shaft extension, and the work string.

[0029] In the following, examples are described of preferred embodiments which are illustrated in the attached drawings, wherein:

[0030] Fig. 1 shows a principle drawing of how a sub is placed in relation to a drilling machine and a work string in a partial operation on a drilling rig;

[0031] Fig. 2 shows at larger scale a cross-section of a sub according to a first embodiment of the invention;

[0032] Fig. 3 shows a cross-section of a sub according to a second embodiment of the invention;

[0033] Fig. 4 shows a cross-section of a sub according to a third embodiment of the invention;

[0034] Fig. 5 shows a cross-section of a sub according to a fourth embodiment of the invention; Fig. 6 shows a cross-section of a sub according to a fifth embodiment of the invention;

[0035] Fig. 7 shows a cross-section of a sub according to a sixth embodiment of the invention; and

[0036] Fig. 8 shows a principle drawing of an arrangement wherein a tubular drive shaft extension is arranged between the drilling machine and a sub according to the invention.

[0037] All position indicators refer to the position shown in the figures.

[0038] The same or corresponding elements are indicated with the same reference number in the figures. For the sake of clarity some elements may not have reference numbers in some of the figures.

[0039] A person skilled in the art will understand that the figures are only principle drawings. The relative ratio between individual elements may also be distorted.

[0040] Reference is first made to Figure 1, wherein reference number 1 discloses a drilling system, here in the shape of a drilling rig, provided with a tower 11 projecting upwards from a drilling deck 15. A drilling machine 12 is hung in a hoisting gear 13 fastened in the tower 11. A tubular sub 14 / saver filling sub 14 according to the invention is screwed tight in a lower threaded portion 121a of a tubular drive shaft 121 of the drilling machine 12. A collar-type elevator 122 hangs from the drilling machine 12. A work string 17 extends from the drilling rig 1 through the drilling deck 15 and down a well 2 formed in a subterranean formation 3. The work string 17 is shown herein hanging in the collar-type elevator 122 with a vertical clearance to the saver filling sub 14. A slips 16 encircles the work string 17 where the work string passes through the drilling deck 15. The slips 16 may be used to hang off the work string 17 in the drilling deck 15.

[0041] Reference is then made to Figure 2, wherein the sub 14 according to the invention is shown in detail. An upper and a lower end portion 141 and 142 respectively, are provided with suitable threaded portions that may be made with different types of threads and in different sizes corresponding to the coupling portions of the drive shaft 121 and the work string 17. The sub 14 is provided with a through centre passage, wherein an upper centre passage portion 143 is cylindrical and a lower centre passage portion 144 is conical, the lower centre passage portion 144 converging from a diameter equal to the upper centre passage portion 143 to an outlet opening 144a of the sub 14. Figure 3 shows an alternative embodiment of the sub 14, wherein the cylindrically formed upper centre passage portion 143 and the convergently formed lower centre passage portion 144 are provided with longitudinal (axial) ridges 146 and 147 respectively, distributed on the circumference of said centre passage portions 143, 144.

[0042] Figure 4 shows the sub 14 with a variant of the embodiment according to Figure 3, wherein only the cylindrically shaped upper centre passage portion 143 is provided with longitudinal (axial) ridges 146.

[0043] Figure 5 shows the sub 14 with a further centre passage shape, the convergently formed lower centre passage portion 144 being provided with an outlet portion 144b that diverges towards the outlet opening 144a.

[0044] Figure 6 shows the sub 14 with yet another centre passage shape, the convergently formed lower centre passage portion 144 being provided with a cylindrically shaped outlet portion 144b.

[0045] Figure 7 shows the sub 14 wherein an interchangeable insert 145 forms the lower centre passage portion 144, herein shown corresponding to the embodiment according to Figure 2, converging from a diameter equal to the upper centre passage portion 143 of an outlet opening 144a of the sub 14. The insert 145 is fastened using per se known fastening technology.

[0046] Combining each of the embodiments according to Figure 4, 5 and 6 with the insert 145 according to Figure 7 is obvious.

[0047] To reduce the risk of damage to the drilling machine's 12 tubular drive shaft 121 as well as to simplify the replacement of the sub 14, it is often preferred to dispose an additional sub 121 b as a direct extension of the drilling machine’s 12 drive shaft 121 as shown by Figure 8. In this situation, the sub 14 according to the invention is coupled to the lower end of said additional sub 121b. This additional sub, also called drive shaft extension 121 b, is of a tubular shape and of a length that provides better access for tools (e.g. tongs (not shown)) used when replacing the (saver filling) sub 14 and in make-up and opening of pipe joints in the work string 17. To a person skilled in the art it is evident that the drive shaft extension 121 b may be made up of several subs screwed together to make up a drive shaft extension of a preferred length. The drive shaft extension 121b may be made up of a saver sub according to prior art. A saver sub according to prior art may potentially make up a part of a drive shaft extension. It should be noted that all embodiments mentioned above illustrate the invention, but do not delimit it, and persons skilled in the art will be able to design many alternative embodiments without deviating from the scope of the attached claims. In the claims, the reference numbers in parenthesis shall not be considered delimiting. The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps not mentioned in the claims. The indefinite articles "a" or "an" before an element do not exclude the presence of more such elements.

[0048] The fact that some features are specified in mutually different dependent claims does not indicate that a combination of these features cannot be used advantageously.

Claims

P a t e n t c l a i m s1. A tubular sub (14) for use between a drilling machine’s (12) tubular drive shaft (121) and a work string (17), alternatively between a drive shaft extension (121b) coupled to the drilling machine’s (12) tubular drive shaft (121), and the work string (17) in a hydrocarbon-related well (2), a thermal-related well (2) or a water- related well (2), wherein the sub (14) acts both as a saver sub to protect a threaded portion (121a) on the drilling machine’s (12) tubular drive shaft (121) or a threaded portion (121c) on the drive shaft extension (121b), and as a filling tool for filling the work string (17) with a liquid when the work string is being run in the well (2), characterised in that an internal tubular lower centre passage portion (144) extending from an internal tubular upper centre passage portion (143) and towards an outlet opening (144a) of the sub (14), deviates from a shape with a constant internal diameter to provide a controlled shape of a liquid jet when the liquid is flowing freely from the outlet opening (144a) of the sub (14).

2. The sub (1) according to claim 1, wherein the internal tubular lower centre passage portion (144) of the saver filling sub (14) is convergently formed towards the outlet opening (144a).

3. The sub (14) according to claim 1, wherein the internal tubular lower centre passage portion (144) of the sub (14) is convergent between the internal tubular upper centre passage portion (143) and an outlet portion (144b) that diverges towards the outlet opening (144a).

4. The sub (14) according to claim 1, wherein the internal tubular lower centre passage portion (144) of the sub (14) is convergent between the internal tubular upper centre passage portion (143) and a cylindrically shaped outlet portion (144b).

5. The sub (14) according to any of the preceding claims, wherein at least one of the internal tubular upper centre passage portion (143) and the internal tubular lower centre passage portion (144) of the sub (14) is provided with longitudinal ridges (146) distributed on the circumference of the internal tubular upper centre passage portion and the internal tubular lower centre passage portion respectively (143 and 144 respectively).

6. The sub (14) according to any of the preceding claims 1-5, wherein the internal tubular lower centre passage portion (144) of the sub (14) is formed in an interchangeable insert (145).

7. The sub (14) according to any of the preceding claims, wherein the sub (14) is a slip ring sub / wired sub.

8. The sub (14) according to any of the preceding claims, wherein the sub (14) comprises a crossover between pipe strings of different dimensions.

9. A drilling system (1) comprising a tubular sub (14) according to any of the preceding claims, wherein the drilling system further comprises: - a drilling machine (12) with a drive shaft (121); and- a work string (17), wherein the annular sub (14) is coupled between the drive shaft (12), potentially a drive shaft extension (121b), and the work string (17).

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