CUTTING TOOL INTEGRATED IN A DRILLSTRING |
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申请号 | EP11751677.3 | 申请日 | 2011-08-12 | 公开(公告)号 | EP2603660B1 | 公开(公告)日 | 2015-06-24 |
申请人 | Sinvent AS; | 发明人 | TAGHIPOUR KHADRBEIK, Mohammad Ali; | ||||
摘要 | |||||||
权利要求 | |||||||
说明书全文 | The invention relates to cutting tools which can be used in drilling oil, gas and deep water wells and mining operations. In particular it is disclosed a cutting tool integrated in a drillstring. Drill bits used to drill wellbores through earth formations typically have a nominal diameter, that is, the diameter that will be created when the drillbit is rotated and impressed axially onto the formation. Frequently it is desirable to enlarge the diameter of the borehole beyond the nominal diameter of the drill bit for several purposes. It is well known that in the process of drilling a deep well for oil and gas production; under reaming of a borehole, it is necessary to treat the borehole wall so as to prevent reduced predetermined diameter of the borehole and also to enlarge the diameter of the borehole drilled by the main bit in front of the drillstring. Numerous attempts have been made to provide proper tools for enlarging a borehole particularly in the oil wells. One of the known prior art is using specialized drill bits, known as bi-centre bits. Bi-centre bits have been developed to create boreholes with drilled diameter greater than the diameter of the opening through which such bits will pass when they are not rotated. It is also known in prior art that roller side cutters are used instead of the solid cutter blades to ream and enlarge a borehole examples of roller side cutters are found in the patent documents Moreover it is known from The publication Other examples of reamers can be found in Enlarging the borehole diameter with cutting blades or with passive rollers is associated with increased drillstring torque. In addition, due to operational limitation such as vibration, the enlarged diameter is limited when using passive cutters. Use of the active rotary cutters is favourable with respect to the torque and will also enable to drill larger borehole than what is possible today. According to the present invention it is an object to provide a tool which overcomes the drawbacks of increased drillstring torque and vibration as known from prior art. In the present invention, a new reamer with special side cutters with self rotating ability is presented. Employing self driven rotational side cutters instead of passive blade and roller cutters for enlarging the borehole is a focused area according to the present invention. Use of the active rotary cutters is favourable with respect to the torque and will also enable to drill larger borehole than what is possible today. In particular the object of the invention is met by a cutting tool integrated in a drillstring where the cutting tool at least comprises one or more side cutters arranged along the longitudinal axis of said drillstring in a reamer housing, where the side cutters are adapted to be rotated independent of the reamer housing around an axis that that is not parallel with the axis of rotation of said drillstring.. According to one embodiment of the invention the cutting tool is specified in that the side cutters are adapted to be rotated by individual driving means. According to one embodiment of the invention the cutting tool is specified in that the dome shaped self driven rotational side cutters extends radially outward from the body of the reamer by means of an actuating system. The rotational side cutters extends radially outward from the body of the reamer relative to the tool housing to a greater extent than the borehole diameter and thereby dig into the borehole sidewalls and remove the material in a milling process. The housing may include at least one actuator for actuating the at least one mill between an extended operating position and a retracted position, in particular to be able to retract the mill or mills during running in or retrieval of the drillstring. The actuating mechanism may according to one aspect of this embodiment comprise one of drilling mud pressure or mechanical means. In another embodiment the cutting tool is specified in that the dome shaped self driven rotational side cutters have non circular cross section. These non circular side cutters can according to one aspect of this embodiment can be rotated without extending radially outward from the housing body where they don't protrude out of the reamer housing in the passive state, and in rotating state the non circular cone, will limp and protrude out of the reamer housing to a greater extent than the borehole diameter and thereby dig into the borehole sidewalls. The crank shaped rotational side cones can have any non circular cross section with aspect ratios larger than one (1.00), where an aspect ratio is defined as the ratio of a length to a width of the cross section shape. So, for example, as defined herein, a circle has an aspect ratio of one, and an ellipse has an aspect ratio greater than one since its major axis (length) is larger then its minor axis (width). According to this embodiment the apparatus may include different sizes of crank shaped rotational side cones with non-circular cross section to enlarge a borehole stepwise, where the smallest side cutter is arranged closest to the drillbit and provide the first stage of the enlargement. In both embodiments, by simultaneous rotation of the tool housing and the side cutters the bore hole can be enlarged to a grater diameter than the original. In addition, both embodiments according to the present invention provide a cutting tool where the driving means can be any of: a mud motor, a hydro motor, a hydraulic motor or an electric motor. Further, a gear transmission system may be arranged to transfer rotational motion from the driving means to the side cutters. The individual driving means can be one of: a hydro motor or an electric motor with direct drive of the side cutters. The invention focus on using active self driven rotational side cutters to enlarge the borehole while in the traditional reamers, passive wings / blades / rollers are used. Other features and advantages according to the present invention will be apparent from the dependent claims. To make the invention readily understandable it will now be described with reference to the drawings in which,
The invention will now be described with support from the drawings in which identical reference numbers indicates similar features. The drawings are included for illustrative purposes so as to make the principle of the invention readily understandable; it shall be appreciated that the person skilled in the art will realize other embodiments than those illustrated by the drawings. In the following the following definition applies; cutters shall be understood as any cutting tools arranged along the drillstring/reamer behind a drill bit with the purpose of drilling bore hole walls. Also, side cutters and cones are used interchangeably and shall be included in the definition of cutters. The basic idea behind the invention is to provide reamers which include one or more cutters arranged behind a drillbit, where at least one of the cutters are rotated by a means different than that of the drillbit. Firstly a general embodiment utilizing self powered cutters will be described; thereafter exemplary embodiments will be disclosed. The new borehole reamer according to the present invention has a cylindrical housing, placed as a part of the drillstring. It consists of at least one rotational cone on the side of the drillstring, almost vertical to the axis of the borehole. The side cones can be rotated by using hydraulic driven/mud motor system placed inside the main housing. However many other means of driving systems can be utilized, it is the individualization of powering the cones/cutters that is important in this context. An internal hydraulic driving system can be placed either, axial to the side cones or axial to the direction of drillstring and to rotate the side cones by using a gear/transmission system or by direct drive. Also the driving means can be electric motors with gear transmission drive or by direct drive. According to the present invention two alternative designs of the rotational side cutters are disclosed.
In both alternatives, the cutting elements mounted on the side cones will rotate around the axis of the cone while the axis of the cone itself will rotate with the drillstring rotation. Use of this concept leads to create new cutting path of the cutting elements which will reduce the drillstring torque. In addition, employing this concept will enable use of the hydraulic energy of the circulating mud for the borehole enlargement process for higher drilling efficiency. By implementing several side cones with different sizes in one tool, it will be possible to achieve a larger borehole compared with the traditional reamers. The direction and axis of the rotations is explained in Schematic of a typical non centric side cutter 32 is shown in Side cones can be rotated by internal mud motors and thereby use the hydraulic energy of circulating mud. However, drillstring mechanical energy or electric motors can also be used for driving the side cones. Each side cone has individual driving system and can be rotated independent of the other side cones. In the particular presented apparatus, the smallest side cutter must be derived first to enlarge the borehole needed to start rotation of the medium cutter. Consequently, the biggest side cutter must be rotated at the final stage where the borehole has been enlarged by the medium cutter. When the three side cones, according to this exemplary embodiment, rotate while the drillstring rotates, the borehole will be fully enlarged. Proper centralizer mechanism may be employed in the entire body of the reamer to centre the tool in the borehole. When tripping the tool in and out of the borehole, especially in the casing section or where the enlarged borehole is not needed, side cutters will stop rotating and be placed in the initial neutral positions as shown in It shall be appreciated that any combination of rotational side cones with non-circular and/or circular cross section which extends radially outward from the body of the reamer with an actuating mechanism can be utilized according to the present invention. Also the cone with non-circular cross sectional design illustrated in |