Patent Application
20110155468
1. Field of the Disclosure
Embodiments disclosed herein relate generally to downhole tools. In particular, embodiments disclosed herein relate to methods and assemblies for drilling a deviated secondary borehole from an existing borehole in geologic formations.
2. Background Art
Traditionally, whipstocks have been used to drill a deviated borehole from an existing earth borehole. The whipstock has a ramp surface which is set in a predetermined position to guide the drill bit on the drill string in a deviated manner to drill into the side of the earth borehole until a secondary borehole is established branching from the existing borehole. In operation, the whipstock is located at a desired depth in the existing borehole by one of several techniques (combined with an anchor or packer that can be set to a desired location in a borehole, set on bottom, or set on plug, etc.), the whipstock is then surveyed when at the desired depth so that the whipstock face can be oriented azimuthally. Then the drill string is lowered into the well and the whipstock serves to deflect or urge the drill bit into the side wall of the bore hole at the angle of the ramp on the whipstock. As the drill string progresses, a secondary borehole is drilled that deviates or branches from the existing borehole. This process of drilling a deviated secondary borehole from an existing borehole is also called “sidetracking.” And more specifically, it may be referred to as open-hole sidetracking when the existing borehole is uncased, that is, the side-tracking initiates directly into the earth formation side wall of the existing borehole.
The typical open-hole sidetracking operation requires at least two trips. The first trip generally involves orienting and setting the whipstock in the open borehole. The second trip generally involves going back into the hole with the bottom-hole-assembly (BHA) with a conventional drill bit to drill the deviated secondary borehole. It is also common that an open hole-side tracking operation requires more than two trips. The anchor or packer may be set in one trip without the presence of the whipstock which is then oriented and set in a separate trip. Or there may be issues with initiating the deviated borehole which requires multiple trips to get started. In general, the elimination of “trips” to accomplish an operation is desirable as each “trip” of the drill string or work string in and out of a well is timely which results in delay and higher drilling costs.
It is also common to drill deviated boreholes from a cased borehole—known as cased-hole sidetracking. The following patents, commonly owned by the current assignee, disclose systems for one-trip milling of cased-hole deviated boreholes: U.S. Pat. Nos. 5,771,972; 5,894,889; 6,102,123; 6,648,068; and 7,207,401. This family of patents also discloses a method that allows “drilling ahead” into the formation further than the typical rat-hole and preferably to the desired target depth (“TD”) of the customer. The configuration and design of the mills that are used to “drill ahead” are a balance of being able to handle the challenging demands of milling the window in the casing and being able to drill to TD with a reasonable rate of penetration (“ROP”). As such, the mills used in these cased-hole sidetracking systems have not been conventional drill bits that, in conventional drilling, are selected or designed to focus on the efficient drilling of the particular lithologies of the earth formation expected to be encountered while drilling to TD.
Accordingly, there exists a need for a one-trip sidetracking tool for sidetracking operations in uncased boreholes.
In one aspect, embodiments disclosed herein relate to a sidetracking tool including a setting tool having an expandable anchor, a whipstock connected to an upper end of the setting tool, the whipstock having a ramp face along an axial length thereof, and a drilling assembly including a drill bit disposed on an end thereof, wherein the drill bit is configured to interface with the ramp face of the whipstock.
In other aspects, embodiments disclosed herein relate to a method of sidetracking including running a sidetracking tool into a borehole, the sidetracking tool including a setting tool having an expandable anchor, a whipstock having a ramp face along an axial length thereof, and a drilling assembly having a drill bit disposed on an end thereof, wherein the drill bit is connected to an upper end of the whipstock. The method further includes actuating the expandable anchor and securing the sidetracking tool in the borehole, applying weight on the drilling assembly and shearing at least one shear screw connecting the drill bit and the upper end of the whipstock, rotating and translating the drill bit downward along an axial length of the ramp face of the whipstock, and deviating the drill bit in a radially outward direction and contacting a sidewall of the borehole to drill deviated hole.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
In one aspect, embodiments disclosed herein relate to a one-trip sidetracking system for sidetracking operations in uncased boreholes. Referring initially to
Setting assembly 20 includes an anchor 22 which may be of the type disclosed in U.S. Pat. No. 7,178,589, which is incorporated herein by reference for all purposes. Anchor 22 may be configured having a large ratio of expanded diameter to unexpanded diameter, which makes it suitable for engaging with borehole sidewall 14. Anchor 22 includes a plurality of slips 24, which are expandable from a running position (i.e., unexpanded) to an anchoring position (i.e., expanded). Anchor 22 has a diameter that is sufficiently less than the diameter of a borehole (not shown) to allow anchor 22 to be lowered through borehole 12, yet large enough such that expandable slips 24 can be expanded to a diameter to fully engage borehole 12. Slips 24 may be hydraulically set by operation of a piston. As the piston is translated by hydraulic pressure, it forces slips 24 to slide on angled ramps (not shown) to extend radially outward until slips 24 engage borehole side wall 14 sufficiently to anchor sidetracking assembly 10 at a desired location in borehole 12.
In alternate embodiments, other devices may be used for setting assembly 20, for example, other types of anchors, packers, which seal the annulus around the packer in addition to anchoring, or some type of device that locks, locates, or sets into a pre-existing structure in the borehole, for example, bridge plugs, plugs of cement, bottom of borehole casing, which remains after a length of casing has been milled away, or some other type of sleeve located in the borehole as will be understood by those skilled in the art.
Anchor 22 has upper end 26, which is connected to bottom end 58 of whipstock 50 at pivot joint 30. Bottom end 28 is opposite of upper end 26 and may be suspended in borehole 12 below slips 24 when slips 24 are set into engagement with borehole side wall 14. If some type of bottom set anchor or packer is used in setting assembly 20, the bottom end will include a mechanism, which may activate slips 24 when the bottom end 28 is pressed against an object in the borehole, e.g., the bottom of the borehole or a plug of some type. Anchor 22 includes a fluid passageway (not shown) which transmits hydraulic pressure to the internal piston that sets slips 24.
Whipstock assembly 50 includes a whipstock 52 that has bottom end 58 connected at pivot joint 30 to upper end 26 of anchor 22. Whipstock 52 has a diameter that is small enough to allow whipstock 52 to be lowered through borehole 12 yet large enough to allow sufficient surface area of ramp face 54 to deviate a drill bit into borehole sidewall 14. Whipstock 52 includes ramp face 54, which, in certain embodiments, may have a concave, arcuate cross-section. In alternate embodiments, the ramp face 54 may be configured having other cross-section shapes as understood by those skilled in the art. As shown in
Referring now to
Cones 116 also have additional inserts 148 mounted in addition to gage inserts 122. The arrangement of gage inserts 122 and additional inserts 148 together with the geometry of cones 116 and the arrangement and orientation of cones 116 on journals 118 relative to bit body 126 is collectively referred to as cutting structure 150. The cutting structure 150 is the portion of drill bit 150 that engages the earthen formation. The design of cutting structure 150 is complex and takes several considerations into account to optimize the design of cutting structure for a given type, or lithology, of earthen formation. For example, the number of inserts on cones 116 may change depending on the hardness of the formation. The angle of journals 118 relative to horizontal, as well as the offset of the journals relative to the centerline of drill bit 110 will also change depending on the type of formation and expected drilling parameters. So while the upper portions for a given diameter drill bit will largely be the same (e.g., pin connection 144, neck 140 and shoulder ends 136 of legs 114), the cutting structure 150 area of drill bit 110 may vary based on the application of the drill bit (e.g., geometry of cones 116, layout and count of inserts 122 and 148, and various relationships between the cones to drill bit body 126).
In other embodiments, a fixed-cutter bit (also called drag bits), which typically include a bit body 22 having a threaded connection at one end and a cutting head formed at the other end, may be disposed at an end of the drilling assembly. The head of the fixed-cutter bit typically includes a plurality of ribs or blades arranged about the rotational axis of the drill bit and extending radially outward from the bit body. Cutting elements are embedded in the raised ribs to cut formation as the drill bit is rotated on a bottom surface of a well bore. Cutting elements of fixed-cutter bits typically include polycrystalline diamond compacts (“PDC”) or specially manufactured diamond cutters. These drill bits are also referred to as PDC bits.
Referring back to
Collar 160 has outer surface 166, which includes mating surface 168 onto which is mated upper end 56 of whipstock 52. Collar 160 is sized such that when finally mounted on drill bit 110, mating surface 168 is set off from diameter Db by a distance equal to or greater than the thickness t, of tongue 66 of upper end 64. In this way, upper end 56 of whipstock 52 does not extend radially beyond the diameter Db of drill bit 110. The extension of tongue 66 axially above cones 116 also may allow for a smooth, gradual engagement of drill bit 110 with ramp face 54 of whipstock 52 once the drill bit starts advancing down borehole 12 during operation. Further, tongue 66 of upper end 56 may be shaped to fit within one of the spaces 132 of drill bit 110 and adjacent mating surface 168 of collar 160. Tongue 66 may be attached to mating surface 168 with shear screws 172 which are designed to shear at a predetermined force, either up and/or down, applied to the drill string.
Referring to
In certain alternate embodiments, the sidetracking assembly disclosed herein may be adapted for use in cased-hole sidetracking, or open-hole side tracking that involves more than one trip.
Advantageously, embodiments of the present disclosure provide a sidetracking assembly capable of fully performing sidetracking operations in a single trip into the borehole. Particularly, overall costs associated with the rig and drilling may be reduced because of the single trip required. In addition, the sidetracking assembly is able to use a conventional drill bit without having to modify the cutting structure of drill bit, which further reduces overall costs of the operation.
While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.
This application, pursuant to 35 U.S.C. §119(e), claims priority to U.S. Provisional Application Ser. No. 61/291,815, filed Dec. 31, 2009, and which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61291815 | Dec 2009 | US |
