Patent Description:
In drilling operations, such as operations on an oilrig, there is sometimes a need to cut tubular structures, such as casings, drill strings, production tubings and risers. Different techniques for cutting tubular structures have been developed. One of the most common ways to cut tubular structures at the drill floor is abrasive cutting from within the tubular structure, diamond wire cutting or a mechanical saw cutting. Typically, the tubular structure is cut in small sections, which are then taken away from the drill floor. Typical cutting time for a <NUM>-inch casing is in the order of a few hours. The problem with above cutting techniques is that it takes too much time. Thus, there is a need for faster cutting techniques.

In a first aspect the invention relates to a cutting tool for cutting a tubular structure, the cutting tool comprising: i) a tool body configured for receiving the tubular structure in an enclosure thereof; ii) an actuator mounted on the tool body at one side of the enclosure; iii) a non-rotatable cutting element provided on the actuator, the actuator with the cutting element being configured for carrying out a translational cutting movement through the enclosure including the tubular structure, and iv) a reaction member mounted at an opposite side of the enclosure of the tool body opposite to the cutting element for applying a reaction force on the tubular structure during cutting, wherein the actuator comprises a hydraulic main cylinder comprising a piston that is coupled to the non-rotatable cutting element via a piston rod, and wherein the actuator comprises an accumulator that is placed in fluid communication with the hydraulic main cylinder for storing and releasing energy, as needed, during the translational cutting movement of the non-rotatable cutting element. The cutting tool of this embodiment of the invention provides for a very efficient, fast and robust cutting of the tubular structure as the energy is applied in much smoother way than without the accumulator. The accumulator is placed inside the piston rod and communicates with the hydraulic main cylinder via a channel. When the actuator is designed very large, in order to be able to cut thick tubular structures, there is a lot of space available within the volume of the piston rod. This volume can be advantageously exploited for housing the accumulator without compromising the strength of the piston rod.

In a first variant the accumulator is used to control the force during cutting. If the forces are not properly controlled, there may be a risk that the system collapses. In order to achieve such controlled cutting, the accumulator is to be coupled to the low-pressure side of the piston in the hydraulic main cylinder, such that the actuator works against the accumulator pressure during cutting, i.e. the accumulator dampens the cutting movement and avoids high forces to be released when the object gives in during cutting.

In a second variant the accumulator is used to increase the force during cutting. In order to achieve such increased cutting force, the accumulator is to be coupled to the high-pressure side of the piston in the hydraulic main cylinder, such that the pressure in the accumulator adds to the hydraulic pressure applied to the high-pressure side of the piston. This variant will generate more force and also lets the cutting tool activate faster.

The effects of the cutting tool in accordance with the invention are as follows. By providing the cutting tool at the drill floor, which uses translational cutting instead of rotational abrasive cutting the cutting of the tubular structure at the drill floor may carried out much faster than the conventional cutting techniques allow. The translational cutting technology has been developed before for subsea applications as known from <CIT>. The inventor realized that such cutting may also be carried out at the drill floor, leading to enormous time gain with cutting times down to <NUM> minutes as experiments have shown. This in contrast with the earlier described abrasive cutting techniques, which can take up to <NUM> hours easily. The cutting tool that is used in the method is the fingerprint of the cutting tool from <CIT>, wherein only the most relevant features are implemented to ensure translational cutting of the tubular structure.

In order to facilitate understanding of the invention one or more expressions are further defined hereinafter.

Wherever the wording "drill floor" is used, this is interpreted to be the heart of any drilling rig (such as an oil rig, but the drill floor may also be on a boat or other floating vessel), i.e. the area where the drill string begins its trip into the earth. It is traditionally where joints of pipe are assembled, as well as the BHA (bottom hole assembly), drilling bit, and various other tools. This is the primary work location for roughnecks and the driller. The drill floor is located directly under the derrick or drill tower. The floor is typically a relatively small work area in which the rig crew conducts operations, usually adding or removing drill pipe to or from the drill string. The rig floor is the most dangerous location on the rig because heavy iron is moved around there. Drill string connections are made or broken on the drill floor, and the driller's console for controlling the major components of the rig are located there.

In an embodiment the reaction member forms part of a further actuator, which further actuator is configured for opening and closing said enclosure for receiving said tubular structure. This embodiment of the cutting tool is a bit more sophisticated. The reaction member that forms part of a further actuator facilitates that the cutting can be carried out quicker, thus saving cutting time.

In an embodiment the reaction member is provided on or integrated with a piston rod or thread bar of the further actuator. This embodiment of the cutting tool is even more sophisticated than the previously-discussed embodiment. Faster cutting is obtained with this embodiment.

In an embodiment the reaction member is provided with a further cutting element directed towards the non-rotatable cutting element for facilitating the cutting. A cutting tool with a further cutting element on the reaction member further speeds up the cutting speed.

In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein:.

Various illustrative embodiments of the present subject matter are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The present subject matter will now be described with reference to the attached figures. Various systems, structures and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.

The figures and description show a cutting tool to be used at the drill floor, which offers an alternative solution to the existing solutions of cutting subsea. An important part of the invention resides in the carrying out of a pure translational cutting movement for severing a tubular structure at the drill floor, such as a casing, a drill string, a production tubing and a riser. Prior art methods disclose time-consuming methods such a diamond wire cutting. A translational cutting movement may be carried out with a huge variety of different tools. In the figures and detailed description only one example is given. It must be stressed that the invention is not limited to this example.

<FIG> shows a perspective view of an embodiment of a cutting tool in accordance with the invention, when provided around a tubular structure. The cutting tool <NUM> may be installed on the drill floor as a mount onto the roughneck (not shown) or as a stand-alone system (not shown), which may be run back and forth (for instance using a rail system) over the Rotary Kelly Bushing (RKB) for each cut. Alternatively, it may be manipulated by means of a crane or manipulator (not shown). <FIG> shows that a tubular structure <NUM> is received in an enclosure <NUM> of the cutting tool <NUM>. The enclosure <NUM> is defined by a tool body <NUM> and a reaction member <NUM>. The cutting tool comprises a linear actuator <NUM> that is coupled to a non-rotatable cutting element <NUM> and configured for carrying out translational cutting movement with said cutting element <NUM>. The reaction member <NUM> comprises a further cutting element <NUM> facing the enclosure, as illustrated. The reaction member <NUM> forms the thread bar of a thread bar actuator, which will be discussed in more detail later.

The cutting tool <NUM> is further provided with a plurality of hoisting connection points <NUM>, which facilitate handling by means of a crane or other type of manipulator (not shown).

<FIG> shows the same perspective view as <FIG>, wherein the cutting element <NUM> is extended for cutting the tubular structure <NUM>. In this figure it is shown that when the linear actuator <NUM> is actuated a piston rod <NUM> onto which the cutting element <NUM> is mounted will come out and squeeze and cut the tubular <NUM> against the cutting element <NUM> on the reaction member <NUM> as illustrated. <FIG> further illustrates that the reaction member <NUM> is part of a further actuator <NUM> (a thread bar actuator), which also comprises an axle with a toothed wheel <NUM> that is driven by a motor <NUM>. When the motor <NUM> is driven the toothed wheel <NUM> rotates runs along the reaction member <NUM> for pulling it in or out depending on the rotation direction.

The embodiment of the cutting tool of <FIG> can cut tubular structures up to <NUM>-inch (<NUM>), and is able to cut drill pipes through the tool joints as well as cemented and lined casings without any problems. Further details with respect to the cutting tool of <FIG> are:.

It must be stressed that within the scope of the current claims also other designs and dimensions of the cutting tool are possible, such that the cutting tool is designed for other dimensions of tubular structures.

<FIG> shows a top-view of <FIG>. In this figure it is illustrated what is meant with the first side S1 and the second, opposite, side S2 of the enclosure <NUM>. At the first side S1 there is provided the cutting element <NUM> and at the second side S2 there is provided the reaction member <NUM> with the further cutting element <NUM>.

<FIG> shows a top-view of <FIG>. This figure illustrates what happens during the cutting of the tubular structure <NUM>. The tubular structure <NUM> is squeezed such that outward projections 1p are formed on the tubular structure <NUM>. The figure also illustrates two guides <NUM> for guiding the cutting element <NUM> during the cutting movement, one on each side of the enclosure <NUM>.

<FIG> show different stages of an embodiment of a method of cutting a tubular structure in accordance with the invention.

In the stage of <FIG> the reaction member <NUM> is fully extended such that the enclosure <NUM> is open to receive the tubular structure <NUM> as illustrated. <FIG> shows the same stage but from a different view angle. In this figure it is visible that the tool body <NUM> has a hole <NUM> for receiving the reaction member <NUM> when it is closed, i.e. moved into the hole <NUM>. The reaction member <NUM> comprises a toothed rack <NUM> at a surface thereof.

In the stage of <FIG> the motor <NUM> has drawn in the reaction member <NUM> by rotating the axle with toothed wheel <NUM> along the toothed rack <NUM> (<FIG>), thereby closing the enclosure <NUM>.

In the stage of <FIG> the cutting of the tubular structure <NUM> is carried out by the linear actuator <NUM> carrying out a translational cutting movement. The figure also shows the piston rod <NUM> that came out of the linear actuator <NUM>.

In the stage of <FIG> the cutting of the tubular structure <NUM> is finished and the reaction member <NUM> has been drawn out again to open the enclosure <NUM>. It can be seen that the tubular structure <NUM> now comprises of two parts, i.e. a first part 1a and a second part 1b. <FIG> shows the same stage as <FIG>, but from a different view angle. In this figure the respective parts 1a, 1b are clearly visible as well as the cutline 1c that separates said parts 1a, 1b. The figure also illustrates the earlier discussed outward projections 1p. These outward projections have a very clear advantage over the known abrasive techniques. When a lined, cemented casing is cut using abrasive techniques and the respective segment is removed it first needs to be pinned such that the inner part of the casing does not fall out when the segment is being lifted. Due to the collapsing of the casing when the cutting tool of the invention is used, such pinning is no longer required, which saves another significant amount of time, between <NUM> and <NUM> minutes!.

<FIG> shows a side view of a further embodiment of the cutting tool in accordance with the invention, wherein the cutting element is retracted. This stage corresponds to <FIG>. <FIG> shows the same side view as <FIG>, wherein the cutting element is extended for cutting the tubular structure. This stage corresponds to <FIG>. This embodiment of the cutting tool <NUM> comprises an improvement in the linear actuator <NUM>, which comprises a main hydraulic cylinder <NUM> in which a piston <NUM> reciprocates and wherein the piston rod <NUM> is connected to the piston <NUM>, as illustrated. The linear actuator <NUM> comprises an accumulator <NUM> for enhancing the cutting of the tubular structure <NUM>. The accumulator <NUM> is conveniently provided inside the piston rod <NUM>, which due to its requirements has quite a large volume anyway. In this embodiment the accumulator <NUM> is in fluid communication with the high-pressure side of the piston <NUM> in the main hydraulic cylinder <NUM> for increasing the cutting force. It must be stressed that different configuration are also possible, yet the current configuration of <FIG> is a very convenient, area efficient, cost-effective solution. This cutting tool of <FIG> provides for a very efficient, fast and robust cutting of the tubular structure as the energy is applied in much smoother way than without the accumulator. It is submitted that the operation of an hydraulic cylinder is known as such and this is not further elaborated upon.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the method steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the invention. Accordingly, the protection sought herein is as set forth in the claims below.

Claim 1:
Cutting tool (<NUM>) for cutting a tubular structure (<NUM>), such as a drill string, at a drill floor of a drilling rig,, the cutting tool (<NUM>) comprising:
- a tool body (<NUM>) configured for receiving the tubular structure (<NUM>) in an enclosure (<NUM>) thereof;
- an actuator (<NUM>) mounted on the tool body (<NUM>) at one side (S1) of the enclosure;
- a non-rotatable cutting element (<NUM>) provided on the actuator (<NUM>), the actuator (<NUM>) with the cutting element (<NUM>) being configured for carrying out a translational cutting movement through the enclosure (<NUM>) including the tubular structure (<NUM>), and
- a reaction member (<NUM>) mounted at an opposite side (S2) of the enclosure (<NUM>) of the tool body (<NUM>) opposite to the cutting element (<NUM>) for applying a reaction force on the tubular structure (<NUM>) during cutting, wherein the actuator (<NUM>) comprises a hydraulic main cylinder (<NUM>) comprising a piston (<NUM>) that is coupled to the non-rotatable cutting element (<NUM>) via a piston rod (<NUM>), and
characterised in that
the actuator (<NUM>) comprises an accumulator (<NUM>) that is placed in fluid communication with the hydraulic main cylinder (<NUM>) for storing and releasing energy, as needed, during the translational cutting movement of the non-rotatable cutting element (<NUM>), wherein the accumulator (<NUM>) is placed inside the piston rod (<NUM>) and communicates with the hydraulic main cylinder (<NUM>) via a channel.