The present invention relates to a plug and to methods for setting and releasing the plug in a well, for example, a hydrocarbon well, as disclosed in the independent apparatus claim and in the independent method claims.
It is common practice to close off the borehole, either temporarily or permanently, by using plugs. The background for this may be that it is desirable, for example, to carry out tests or maintenance in the well. The plugs are usually run down the well using a running tool. When the plug has reached the desired depth in the well, it is secured to the surrounding casing or borehole wall using anchoring elements. The borehole is subsequently sealed, often by using packers which seal the area between the pipe or plug and the borehole wall. The bridge plug shown in U.S. Pat. No. 6,220,348 B1, and the whole running tool, must be pulled out of the well if another operation is to be carried out in the well, which will mean a great deal of extra time and costs.
Known plugs for use in wells have the disadvantage that the plugs require maintenance between each operation.
It is usual to set and release plugs by means of rotation, but it can be difficult to achieve controlled rotation at great well depths. There are several potential sources of error which make the setting and release hazardous. One such source of error could be left-hand (anti-clockwise) rotation, which may result in equipment such as drill pipes or plugs being unscrewed from one another.
It is an object of the invention to resolve some of the drawbacks of the prior art. The object is achieved by means of a plug and methods for its setting and release according to the independent claims, with embodiments of the invention disclosed in the dependent claims. The setting and release take place essentially by means of axial movement of the pipe. By this is meant that an up-and-down movement applied to the plug is transmitted into a rotational movement that applies to the plug a moment which it wishes to release through a locking system. Another object is to provide a plug which can be used for several operations in a well with little call for maintenance of the plug between the different operations.
In the present invention, according to independent claim 1, a plug for a hydrocarbon well is defined, wherein the plug can be held in place relative to a casing/borehole, and wherein the plug further comprises a slip actuator for setting and releasing slips, a locking element in contact with the slip actuator, and one or more resilient packing elements which are adapted for sealing against the casing/borehole wall, and wherein the locking element comprises multiple parts having internal threads which constitute an enclosure around threads on a pipe, and where on the radial outer surface of the locking element there are arranged resilient elements, and that
The invention also relates to a method for setting the plug in a well, wherein the setting is activated by an axial movement of the pipe, and where the movement further causes a guide sleeve to apply a force on the locking element which, by means of its high-pitch threads against the pipe, will slide over the threads and exert a force on the slip actuator which presses the slips out into firm engagement with the casing/borehole wall. By high-pitch threads here is meant threads that will rotate off a corresponding threaded part in only a few turns.
The invention relates also to a method for releasing the plug wherein an axial movement of the pipe activates the release of the locking sleeve from the locking element, such that the locking element is free to rotate off the threads on the pipe and the slips are released. Axial movement may be a movement up or down, or a combination thereof.
The setting or release of the plug should not take place unless desired. Up and down movement of the vessel, as a consequence of the rolling of the sea, may inadvertently start the setting. To avoid undesired setting and release, a first and a second hydraulic timer may be provided in connection with the plug for setting and release, respectively. The timers, one for setting and one for release, ensure that the setting or release does not start until the pressure from the surface acts over a given time period. The timers each consist of two hydraulic fluid chambers, where fluid from one of the chambers starts to flow over into the other chamber as a result of pressure that is applied to the pipe from the surface. If the pressure is not applied for a sufficiently long time, as, for example, on the heave of the waves, all the fluid will not flow between the chambers, and the setting or the release will not be started. Once all the fluid has flowed between the chambers, the setting or the release will start.
On the pipe there may be provided at least one fixed pin that is movable in a recess in a guide sleeve on the plug. The recess in the guide sleeve may be helical. This makes it possible for the operator to know at all times where the plug is in the setting or release process, in that the pin element follows the axial movements of the pipe, up-down-up, as the pipe is pushed down into the well or pulled upwards. An axial movement of the pipe, and thus of the pin in the recess, will cause the axial movement to be transmitted into a rotational movement of the guide sleeve depending on the form of the recess.
A holding member with radially acting elements can hold the plug essentially fixed to the casing/borehole wall during the setting. During the setting, but not necessarily during the release, the holding member will be in end contact with a guide sleeve, and a locking element will be in end contact with the second end of the guide sleeve.
In an embodiment, the setting involves that a locking element with locking grooves, which during setting of the plug is so arranged as to allow the locking element on an axial movement of the pipe to slide over corresponding threads on the pipe, engages with corresponding locking pins on the locking sleeve and is prevented from being screwed off the threads. The locking sleeve is held fixed in the rotational direction, but is movable in an axial direction relative to the pipe. The configuration of the locking grooves on the locking element and the locking pins on the locking sleeve may be any configuration suitable to prevent rotation. On locking, and before the locking element is locked in the locking sleeve, the axial movement of the pipe will set slips, and the plug will be anchored to the casing/borehole wall. Resilient packing elements arranged on the plug seal against the casing/borehole wall when compressed. In connection with the compressible resilient packing elements, one or more backstop elements are provided which are fixed relative to the pipe. The backstop elements follow the movement of the pipe, and a further movement of the pipe, after the slips have been set, will cause the resilient packing elements to be compressed between the slips and the backstop elements.
When releasing the plug, the pipe is by means of the running tool run down to the plug. A timer controls the activation of the release. After the activation of the timer, the pipe is moved a given length. This movement causes the slips to be released thereby releasing the anchoring against the casing/borehole wall, and the engagement between the locking grooves on the locking element and the locking pins on the locking sleeve is broken. On release of the slips, the holding force from the slips against the resilient packing elements is removed. The resilient packing elements will therefore no longer be kept compressed, but are free to expand in an axial direction. The axial force from the resilient packing elements will act on the locking element such that the locking element rotates off the threads on the pipe.
One embodiment of the invention will now be described with reference to the attached drawings, wherein:
Reference is first made to
The locking element 5 has arranged at one of its end portions locking grooves 11 capable of engaging with corresponding locking pins 19 in a locking sleeve 7. The locking sleeve 7 is fixed in the rotational direction but is movable in an axial direction, see
At the upper end of the plug 1, resilient packers 20 are provided which seal between the pipe 15 or plug 1 and the casing/borehole wall. In connection with the resilient packing elements 20, backstop elements 41 are arranged thereabove that are fixed relative to the pipe 15 and follow the movement of the pipe 15.
During the running down of the pipe 15, the pin 3 is in the position shown in
The time interval for how long pressure is to be applied to the pipe 15 is determined in advance, and is given by how long it takes before all fluid in the hydraulic timer 2 has migrated from the first chamber to the second chamber, see
When all fluid has flowed over from one chamber to the other chamber in the first hydraulic timer 2, the setting of the plug 1 starts. A holding member 10 with radially acting elements 12 on the plug 1 essentially holds the plug 1 fixed to the casing/borehole wall, see
When the plug is to be released from the casing/borehole wall, the pipe 15 is run down into engagement with the plug by the associated running tool 13, see
The invention has now been explained with reference to one embodiment. A person of skill in the art will understand that changes and modifications may be made to the embodiment described which are within the scope of the invention as defined in the attached claims.
Number | Date | Country | Kind |
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20110908 | Jun 2011 | NO | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB2012/053191 | 6/25/2012 | WO | 00 | 2/4/2014 |