FISHING TOOL
A fishing tool for cable-based retrieval of equipment from a borehole comprises a seat cone, an inner spring that tensions the seat cone, a locking cone that is arranged external to the locking cone and which is tensioned by an outer spring, and at least one latch that is pivotal to a position for gripping the equipment by movement of the seat cone and the locking cone with the aid of the respective springs.
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The present invention relates to a fishing tool for cable-based retrieval of equipment from a borehole.
When drilling for oil both onshore and offshore, there is often a need to pull out the drill string, which consists of pipe sections that are screwed together, and the associated bottom drill bit. During pull-out, i.e., the tripping operation, it is most usual that three such connected pipe sections, often referred to as a stand, are taken out in successive to order and then set aside or stacked on a separate pipe rack.
During drilling procedures problems sometimes arise because the drilling mud, owing to inadequate or no cleaning at all, remains on the inside of the wall of the pipe sections after pull-out of the drill string during the tripping operation. The mud may thus dry and form hard flakes or clumps on the pulled-out pipe sections. When these pipe sections are to be redeployed, hard clumps or flake particles may be pumped down to the drill bit, and thus block one or more of its nozzles. In the worst case, the result of this is extensive damage to the drill bit, or also that problems arise in connection with, for example, downhole tools and motors.
Another drawback of inadequate removal of drilling mud during the tripping operation is undesired spillage of drilling mud on the deck of the drilling rig or in storage areas in the vicinity of the pipe rack. This causes unnecessary work cleaning the deck and disposing of the mud spillage, and, in the worst case, it could result in injuries due to a slippery and muddied deck.
To remedy the problems mentioned above, many alternative solutions are found in the patent literature, where, for instance, WO-A1 2006/006872 provides an example of wipers for internal removal of drilling mud from the drill string. In this case, the wiper is made having a mass and a volume that allow it to float on top of the drilling mud during the tripping operation. The wiper is bellows-shaped and comprises a weight that is connected to its upper part. Furthermore, the wiper is equipped with one or more channels past or through it so as to allow through-flow of the drilling mud. Reference is also made to this document as such for a closer understanding of the mode of operation of this type of wiper, without this thereby being regarded as limiting in respect of the use of other wiper types in the present invention.
Fishing tools that are used to retrieve equipment from a borehole are based on the equipment being secured in an appropriate manner downhole. The triggering mechanism in such fishing tools is therefore made to be screwed, forced over or to have gripping claws which require a hard blow for actuation. In this connection, there exist s breakable shear pins. Should the equipment in the borehole on the other hand be constituted of another type that is movable and thus not secured in a fixed position prior to retrieval, the traditional fishing tools are quite obviously unsuitable.
The wiper disclosed in WO-A1 2006/006872, which floats on the liquid column of io drilling mud inside the drill string, is a good example to illustrate equipment that is unsuitable for use with traditional fishing tools. In this case, it is most probable that the fishing tool will not manage to grip the fish neck on the wiper, but instead push it down into the drilling mud.
To solve this problem, there is proposed, according to the present invention, a fishing tool for cable-based retrieval of equipment from a borehole, characterised in that the tool comprises a seat cone, an inner spring that tensions the seat cone, a locking cone which is arranged externally to the locking cone and which is tensioned by an outer spring, and at least one latch that is pivotal into a position for gripping the equipment by movement of the seat cone and locking cone with the aid of the respective springs.
It is thus achieved that it is not only equipment which is fixed in the borehole that can be gripped in a reliable manner for retrieval to the surface, but also any other equipment that is movably mounted and therefore earlier could not be fished up without causing substantial problems during the fishing operation.
To facilitate the pivoting into the gripping position, the at least one latch can be mounted pivotally on a pivot, whilst the locking cone is arranged slidably on a sleeve, which at the lower end surrounds the seat cone.
Furthermore, to effect the gripping, the sleeve can be equipped with balls that are adapted to move from a recess in the lower end of the locking cone to a recess in the upper end of the seat cone. During this movement, the upper edge of each latch is pressed out when the locking cone is released and pressed downwards by the outer spring. Furthermore, the lower end of the seat cone is configured having a seat that is intended to rest against an upper end of the equipment for displacing the seat cone along the guide with simultaneous displacement of the locking cone in the opposite direction during actuation of the fishing tool for gripping the equipment.
Other advantageous features of the present invention are set forth in the dependent claims and in the description below.
A more detailed explanation of the present invention will be given below with reference to the appended drawings, wherein:
With reference to
Details in connection with the fishing tool as such can be seen from
Furthermore, the tool has a locking cone 12 which is arranged external to the locking cone, and which is tensioned by an outer spring 13, as shown in
To be able to grip the equipment 1, the fishing tool is equipped with at least one latch 14 that is pivotally mounted to a pivot 15, in such a way that the latch pivots to the position that is shown in
For maintaining the seat cone and locking cone 10, 12 in their respective end positions before and after actuation of the fishing tool, the sleeve 16 is equipped with balls 17. As shown in
From the explanation above, it will be understood that the present invention provides a fishing tool that can easily be actuated simply by contact between the seat face and the upper end of the equipment that is to be fished for retrieval to the surface above the borehole. This contact causes the seat cone and locking cone to enter reciprocal displacement along the guide and the sleeve respectively by means of elastic force in the inner and outer spring. See
Although in the above reference was made to the wiper disclosed in WO-A1 2006/006872 as an example of relevant equipment for fishing, it will be understood that all other types of downhole tools, instruments and the like can be fished with the present tool. Furthermore, there is nothing to suggest that the tool according to the invention is necessarily only useful for use in connection with the retrieval of equipment which is freely movable in the borehole, as it is also conceivable that it can be used for equipment that is fixed in, for example, a drill string.
In addition, the fishing tool may in a non-illustrated way be equipped with:
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- a mechanism for releasing the fishing tool from the equipment if a predetermined load/tension in the cable is exceeded, i.e., in the event of an overload, or a time-determined release mechanism.
- a safety mechanism to prevent movement of the seat cone before contact with the equipment is secured.
- an adaptation to an internal or external profile on the equipment.
Claims
1. A fishing tool for cable-based retrieval of equipment from a borehole, wherein the tool comprises a seat cone, an inner spring that tensions the seat cone, a locking cone that is arranged external to the locking cone and which is tensioned by an outer spring, and at least one latch that is pivotal to a position for gripping the equipment by movement of the seat cone and locking cone with the aid of the respective springs.
2. A fishing tool according to claim 1, wherein the at least one latch is pivotally mounted on a pivot.
3. A fishing tool according to claim 1, wherein the locking cone is arranged slidably on a sleeve which at a lower end surrounds the seat cone.
4. A fishing tool according to claim 1, wherein the seat cone is slidably mounted on a guide.
5. A fishing tool according to claim 4, wherein a lower end of the seat cone is configured with a seat that is intended to rest against an upper end of the equipment for displacement of the seat cone along the guide with simultaneous displacement of the locking cone in the opposite direction during actuation of the fishing tool for gripping the equipment.
6. A fishing tool according to claim 1, wherein the sleeve is equipped with balls that are adapted for moving from a recess in a lower end of the locking cone to a recess in an upper end of the seat cone.
7. A fishing tool according to claim 1, wherein the at least one latch is provided with profiling that is adapted to be connected to a correspondingly shaped portion on an upper end of the equipment when gripping the equipment.
8. A fishing tool according to claim 1, wherein the tool comprises an outer housing consisting of an upper tubular piece and a lower tubular tip.
9. A fishing tool according to claim 8, wherein an upper end of the tubular piece of the housing is fastened to a top connector equipped with an attachment means for a fishing cable.
Type: Application
Filed: Jun 6, 2010
Publication Date: May 17, 2012
Applicant: 2K TOOLS AS (OSLO)
Inventors: Kjell Mikalsen (Narvik), Ketil Botn-Mark (Narvik)
Application Number: 13/375,756
International Classification: E21B 31/08 (20060101);