Area of the invention

The present invention concerns a lifting object for lifting and handling of collar-devoid components that enter into a so-called bottomhole assembly ( "BHA" ) . When in position of use, the bottomhole assembly will be attached to a lower end of a drill string.

Typically, such a bottomhole assembly will comprise a drill bit together with weight pipes ("drill collars") arranged immediately behind the drill bit. If desirable, the bottomhole assembly may also comprise other downhole tools. Thus, the bottomhole assembly may comprise one or more data gathering units for real time gathering of formation data or similar, so-called MWD-units ("Measurement While Drilling") or LWD- units ("Logging While Drilling"); downhole motors for rotation of drill bits or milling tools during a drilling operation; directional drilling tools for use during directional drilling; fishing tools for connection to and withdrawal of lost downhole objects; and/or jarring tools for disengagement of stuck pipes and objects, etc.

The lifting object may also be used for handling of components that enter into a completion string for a well. Upon being introduced into or withdrawn from the well, such a completion string will also be attached to a lower end of a drill string. Thereby, the completion string will also form some kind of bottomhole assembly on the drill string.

Background of the invention

The background of the invention is related to problems associated with use of so-called lift subs for lifting and handling of drill collars, data gathering units, downhole - motors, directional drilling tools, fishing tools, jarring tools, etc. entering into a bottomhole assembly.

These problems concern, in particular, the working safety of the drilling personnel handling such conventional lift subs. The problems also relate to unnecessary time breaks and associated cost increases due to use of conventional lift subs. The last -mentioned problems are of substantially greater importance in relation to well drilling offshore. Moreover, problems exist in relation to storage, transport and maintenance of such lift subs.

Prior art and disadvantages thereof

Generally, a tubular component entering into a bottomhole assembly has an even external diameter throughout the entire length thereof. For this reason, the normal practice is to connect such a component to a lift sub so as to be able to lift and handle the component during assembly or disassembly of the bottomhole assembly.

Such a lift sub is also used in context of assembly or disassembly of a component entering into a completion string, in which context the lift sub is generally referred to as a handling joint. Such a handling joint may also remain connected to the component during incorporation into the completion string, whereby the handling joint accompanies the completion string when being inserted into the well. This has to do with the fact that various components in a completion string of- tentimes comprise relatively delicate appliances and equipment to be handled carefully and hence should not be exposed to load-bearing and rough contact with slips or similar during the insertion process into the well. For this reason, the particular component in question is oftentimes connected to a handling joint capable of enduring large loads and rough handling better.

Such a lift sub resembles a drill pipe but is shorter than the drill pipe, typically ca. 1 meter long. Similar to the drill pipe, the lift sub is provided with radially enlarged portions at the respective ends thereof. As such, the lift sub is provided with an upper end portion comprising a radially enlarged lift collar which is chamfered down toward the base pipe of the lift sub, and also a lower end portion comprising a radially enlarged male-threaded connector for connection to the particular component for/in the bottomhole assembly, which may also be comprised of a completion string.

Upon having connected the male-threaded connector to a corresponding, threaded socket in the particular component in question, a so-called pipe elevator is introduced around the lift sub and is connected tightly around the lift collar.

Then the lift sub and connected component may be lifted and handled for connection to, or disconnection from, a bottom- hole assembly. The pipe elevator is used, in a corresponding manner, to run the drill string into or out of a well, oftentimes over a well length spanning several thousand meters. Generally, such a pipe elevator is connected to a drawworks in a drilling derrick via suitable lifting bails. In addition, the pipe elevator is structured with an internal shape and size that allows the pipe elevator to fit tightly around the lift collar on the drill string or the lift sub.

Moreover, it is common to use the same pipe elevator for han- dling of all sizes of drill strings and lift subs used to form one or several borehole sections in a well. Upon introducing suitable inserts inside the pipe elevator, the pipe elevator may be adapted to the particular size of drill string or lift sub in question. The work of mounting/ dismounting or replacing such inserts in the pipe elevator usually takes 15 minutes. Given that such inserts are relatively big and heavy, the lifting and handling thereof will involve an increased risk of harming the drilling personnel carrying out such a work task. When considering safety, but also time and hence cost, it is therefore desirable to limit the number of replacements of inserts to a necessary minimum.

If the drill string comprises drill pipes of a certain size screwed together into a long pipe string having, for example, a length of several thousand meters, it will be the external diameter of the drill pipe and its lifting collar that will dictate the size of the inserts in the pipe elevator.

If, however, the drill string is comprised of a so-called tapered drill string, which comprises at least two consecutive drill string sections having decreasing external diameters, it will be the external diameter of the drill pipe and its lift collar in each drill string section that will dictate the size of the pipe elevator's inserts. For a tapered drill string, a certain size of inserts must therefore be used for each drill string section, which requires replacement of the pipe elevator's inserts when a new drill string section is to be handled. However, such a replacement of inserts is required. Insofar as each drill string section may be several thousand meters long, the replacement nevertheless constitutes a very small portion of the total work of screwing together or dismantling each drill string section.

Yet further, a well is formed by drilling consecutive bore- hole sections having successively decreasing borehole diameters. For this reason, drill strings and bottomhole assemblies having different external diameters, lengths and/or types of thread connections are used. This is also applicable to the many components that enter into the various bottomhole assemblies used during the well drilling, or which are used in a completion string for the well . To allow this number of different components to be lifted and handled, many lift subs having different external diameters and/or types of thread connections must therefore be used, in which said external diameter may refer to the base pipe of the lift sub and/or to the lift collar. This usually implies that several different lift subs must be available for allowing effective mounting and dismounting of the different bottomhole assemblies used during the well drilling, or which are used in the completion string of the well.

Provision of the correct types and numbers of lift subs for a drilling operation, however, requires good operational predictability, good well planning and good availability of such lift subs. This does not always reflect the particular situation for a well and/or a drilling rig. Due to lacking and/or wrong types of lift subs, the drilling personnel frequently have to improvise and have to carry out an extraordinary work effort to allow a well operation to continue. Such extraordinary work efforts oftentimes involve an increased risk of harming the drilling personnel as well as unnecessary time breaks and associated cost increases for the well drilling.

As an example of this, the drilling personnel may have to use a lift sub that does not match the particular inserts in the pipe elevator in order to lift and handle a particular component for a bottomhole assembly. This, however, requires an extraordinary work effort owing to the fact that firstly the pipe elevator's inserts have to be replaced with other inserts that fit tightly around the lift collar of the lift sub, upon which the other inserts have to be replaced with the original inserts after the handling of the component. Each such extraordinary replacement increases the risk of harming the drilling personnel and uses ca . 15 minutes of rig time .

Another example of this relates to various components entering into a bottomhole assembly, the components of which are frequently shipped to the drilling rig having lift subs already connected thereto. For example, this may relate to downhole data gathering units, downhole motors, directional drilling tools, fishing tools or jarring tools. Alternatively, it may relate to various components entering into a completion string to be installed in a well. Unfortunately, it is a common occurrence that such components are shipped to the drilling rig having the wrong type of lift subs connected thereto with respect to the size of those pipe elevator inserts to be used for the drill string within which the particular component is to enter. Also in this case, an extraordinary work effort is required to allow the mounting of a bottomhole assembly to continue, which also may be comprised of said completion string. One solution is to replace the erroneous lift sub, which is connected to the component, with another lift sub having a lift collar fitting tightly into those pipe elevator inserts being used during drilling of said borehole section. Such a replacement increases the risk of harming the drilling personnel and uses ca. 15 minutes of rig time. Another solution is to replace the pipe elevator's inserts with other inserts fitting tightly around the lift collar on the erroneous lift sub, and replace the other inserts with the original inserts in the pipe elevator, as mentioned in the preceding example. The common practice of using many different lift subs for effective mounting and dismounting of a bottomhole assembly is also associated with other disadvantages. A large number of lift subs requires a larger storage area, more extensive transportation and more extensive maintenance than that corresponding to a smaller number of lift subs. These disadvantages will also influence negatively on the aspects of safety, cost and technology associated with drilling operations, and particularly drilling operations offshore.

Objects of the invention

A principal object of the invention is to remedy, or at least reduce, the above-mentioned disadvangtages associated with the known use of lift subs for lifting and handling of drill collars and possible other components entering into a bottom- hole assembly for a drill string, but also for handling of components entering into a completion string for mounting onto a lower end of the drill string.

The object of the invention is also to reduce the risk of harming personnel occupied with the handling of such lift subs .

Another objective of the invention is to avoid, or at least reduce, unnecessary time breaks and associated cost increases related to use of conventional lift subs.

A further object of the invention is to reduce the number of lift subs used in context of a drilling operation or completion operation, thus reducing problems related to storage, transportation and maintenance of such lift subs.

General description of how to achieve the objects

The objects are achieved by virtue of features disclosed in the following description and in the subsequent claims. In a first aspect of the invention, a lifting object for a component for a bottomhole assembly, which also may be comprised of a completion string, is provided. However, hereinafter the term "bottomhole assembly" will be used both with regard to a conventional bottomhole assembly, which at least comprises various drill collars, and with regard to a completion string for mounting onto a lower end of a drill string.

The lifting object is cylindrical and comprises a radially enlarged, first lift collar arranged at a first end portion of the lifting object. The lifting object also comprises a threaded connector arranged at a second end portion of the lifting object, wherein the threaded connector is structured in a manner allowing it to be connected to said component.

The distinctive characteristic of the lifting object is that it also comprises at least one further and radially enlarged lift collar arranged between the first end portion and the second end portion of the lifting object; and

- wherein said further lift collar has an external diameter which is different from the external diameter of the first lift collar.

For example, the lifting object may comprise one, two, three or several further lift collars.

The cylindrical lifting object may be tubular and hence is hollow, such as in conventional lift subs. Use of tubular and hollow objects is most common in a drilling context and implies reduced weight of the particular object.

Alternatively, the cylindrical lifting object may be massive. Such a lifting object will be heavier and stronger than that of a corresponding, hollow object. Moreover, said further lift collar may have an external diameter which is less than the external diameter of the first lift collar. Upon using more than one further lift collar, the further lift collars may have successively decreasing, external diameters relative to the external diameter of the first lift collar.

Thus, the present lifting object comprises at least two lift collars having different external diameters. Each lift collar on the lifting object may have an external diameter and shape corresponding to the external diameter and shape on the lift collar of the drill pipe size being used for a particular drill string or drill string section. By so doing, the lifting object is structured for use together with at least two drill strings or drill string sections of different sizes. During drilling of a well, it is common to use at least two drill string sizes. Each of the lifting objects to be used for such a well drilling, may therefore be provided with at least two different lift collars of sizes matching the particular sizes of drill strings (and hence drill pipes) to be used during the well drilling.

The latter feature has the advantageous effect, among other things, of allowing the number of lift objects which must be available to allow the well drilling to be carried out efficiently, to become far smaller than that of using conventional lift subs. Approximately half the number of required lift objects is estimated. A smaller number of lifting objects requires less storage area, less transportation and less maintenance than the corresponding for conventional lift subs. These advantages influence positively on the aspects of safety, cost and technology associated with drilling operations, and particularly drilling operations offshore. Furthermore, a lifting object provided with at least two different lift collars will have the advantageous effect of allowing the lifting object to match various sizes of inserts in said pipe elevator. By so doing, the drilling personnel avoids having to replace inserts in the pipe elevator due to lacking and/or wrong types of lift subs, as described for conventional lift subs. Also in this situation the risk of harming the drilling personnel is reduced, simultaneously avoiding or reducing unnecessary time breaks and associated cost increases.

Use of the present lifting object will also have an advantageous effect in the above-mentioned situation where a component for a bottomhole assembly is shipped to the drilling rig having a wrong type of lift sub connected thereto relative to the particular inserts in the pipe elevator. If the component is shipped to the drilling rig having a lift sub of the present type already connected to the component, the multi- collar lifting object will reduce the probability of the lifting object not fitting into the particular inserts in the pipe elevator. As an alternative, the component may be shipped to the drilling rig without having any lifting object connected to the component. In the latter case, a lifting object of the correct type may be stored on the drilling rig, whereby the correct lifting object may be connected to the component after arrival on the drilling rig. In both cases, an extraordinary work effort by the drilling personnel is avoided, whereby the risk of harming the drilling personnel is reduced. Simultaneously, unnecessary time breaks and associated cost increases for the well drilling are avoided.

In a second aspect of the invention, a use of a lifting object provided with at least two separate, radially enlarged lift collars having different external diameters for lifting and handling of a component for a bottomhole assembly is provided.

Hereinafter, a non-limiting exemplary embodiment of the invention will be shown.

Short description of the figures of the exemplary embodiment

Figure 1 shows a front elevation, partially in section, of a lifting object according to the invention, wherein a pipe elevator is provided internally with a first set of inserts which encloses, when in position of use, a first lift collar on the lifting object; and

Figure 2 shows a front elevation, partially in section, of the lifting object according to figure 1, but wherein said pipe elevator is provided internally with a second set of inserts which encloses, when in position of use, a separate and smaller, second lift collar on the lifting object.

The figures are somewhat schematic and simplified with respect to richness in detail, relative sizes and positions of the elements shown in the figures.

Detailed description of the exemplary embodiment

Figures 1 and 2 show a lifting object according to the invention formed as a tubular and hollow lift sub 2.

In this embodiment, the lift sub 2 comprises radially

enlarged, first lift collar 4 arranged at a first end portion 6 of the lift sub 2. This first lift collar 4 is radially enlarged with respect to the diameter d _x of an immediately adjacent, first base pipe portion 8 of the lift sub 2. The first end portion 6 is also provided with an internal female thread portion 10 structured for connection to a threaded pin (not shown) on a lift ring, lift cap, lift nubbin or similar. At the second end portion 12 of the lift sub 2, the end portion of which is also comprised of a radially enlarged pipe portion, the lift sub 2 is provided with a male-threaded connector 14 structured for connection to a corresponding, threaded socket in a component (not shown) for or in a bot- tomhole assembly (not shown) .

According to the distinctive characteristic of the invention, the lift sub 2 also comprises a further, and radially

enlarged, second lift collar 16 arranged between the first end portion 6 and the second end portion 12 of the lift sub 2. In this embodiment, the second lift collar 16 has an external diameter D ₂ which is smaller than the external diameter Di of the first lift collar 4. The second lift collar 16 is radially enlarged relative to the diameter d ₂ of an immediately adjacent, second base pipe portion 18 of the lift sub 2. This second base pipe portion 18 is located between the second end portion 12 of the lift sub 2 and the second lift collar 16.

Figures 1 and 2 also show a conventional pipe elevator 20 comprising two interlinked elevator parts 20a and 20b which, when in position of use, may open and close around a lift collar on a drill pipe in a drill string, or around a lift collar 4, 16 on the lift sub 2. In its position of use, the pipe elevator 20 is connected to a drawworks in a drilling derrick via suitable lifting bails (not shown) .

In figure 1, the pipe elevator 20 is shown provided internally with a first set of inserts 22 tightly enclosing the first lift collar 4 and a part of the first base pipe portion 8, the lift collar 4 being located at the top of the lift sub 2 when _^ in position of use.

In figure 2, however, the pipe elevator 20 is shown provided internally with a second set of inserts 24 tightly enclosing the second lift collar 16 and a part of the second base pipe portion 18, the lift collar 16 being located below the first lift collar 4 on the lift sub 2 when in position of use. The inserts 24 in the second set are thicker than the inserts 22 in the first set. Thereby, the thicker inserts 24 form a smaller internal diameter than the internal diameter of the thinner inserts 22 when assembled in the pipe elevator 20.

Thus, the figures clearly show that the present lift sub 2 is structured in a manner allowing it to be used together with any set of inserts 22, 24 in the pipe elevator 20. The one and same lift sub 2 may therefore be used for lifting and handling of components entering into bottomhole assemblies for two different sizes of drill strings or drill string sections. Such a lift sub 2 will also allow two conventional lift subs to be replaced with only one lift collar each.

If required or desirable, the lift sub 2 may also be provided with further lift collars, thereby allowing it to be used in connection with three or more different sizes of drill strings or drill string sections, and for mounting or dismounting of components entering into bottomhole assemblies thereof .