Bottomhole assembly

Abstract

A bottomhole assembly for performing a wellbore operation comprising a plurality of full-gauge components that are each radially expandable and retractable between respective first positions and respective second positions, wherein the first positions each have a diameter which is substantially the same as that of the wellbore and wherein the second positions each have a diameter which is substantially smaller than that of the wellbore. The plurality of full-gauge components comprise a full-gauge drill bit and one or more full-gauge stabilizers. The bottomhole assembly may further comprise a rotary steerable system and/or a motor.

Description

BACKGROUND[0001]Embodiments of the present disclosure relate to a bottomhole assembly (BHA) for performing a wellbore operation and more particularly but not by way of limitation to a BHA comprising a drill bit and a stabilizer that are both radially expandable and retractable.[0002]A borehole is often drilled in the ground for the extraction of a natural resource such as ground water, brine, natural gas, or petroleum. Such a borehole is also often referred to as a wellbore.[0003]A bottomhole assembly (BHA) comprises the lower portion of the drillstring used in drilling a wellbore, and it generally comprises, from the distal end to the surface, one or more of the following, a drill bit, a bit sub, stabilizers, drill collars, heavy-weight drillpipe, jarring devices and crossovers for various threadforms. The BHA provides weight-on-bit (WOB) for the drill bit to break the rock, survive a hostile mechanical environment and provide the driller with directional control of the well. The B...

AI Technical Summary

Benefits of technology

[0031]The expandable drill bit may comprise a drill bit and a near bit reamer, wherein the drill bit may be a roller cone bit or a fixed cutter bit. Such an arrangement makes use of conventional drill bits and conventional near bit reamers, which are readily available. Thus, it's more convenient and cheaper to provide a BHA with such an expandable drill bit.

[0032]The near bit reamer may be capable of under-reaming. Accordingly, it may be a near bit reamer, a near bit under-reamer, or a near bit reamer capable of both reaming and under-reaming. In a conventional BHA, the drill bit has a diameter which is substantially the same as that of the wellbore so that it can drill a wellbore of the same diameter, and the near bit reamer has a maximum diameter which is larger than that of the wellbore so that it can be expanded and used to enlarge the wellbore to a larger diameter. By contrast, if a conventional drill bit and a conventional near bit reamer are provided in accordance with embodiments of the present disclosure, the drill bit has a diameter which is substantially smaller than that of the wellbore so that, when the BHA is retracted, it can run through the wellbore more easily especially during directional drilling, and the near bit reamer has a maximum diameter that is substantially the same as that of the wellbore so that it can drill a wellbore of the same diameter. Accordingly, the near bit reamer or under-reamer of the present invention, when expanded, performs the function of a drill bit in conventional applications. Furthermore, in embodiments of the present disclosure the near bit reamer can be retracted to an under-gauge position for ease of running through the wellbore.

Problems solved by technology

When the drill bit becomes dull or stops making progress for other reasons, it must be taken out of the wellbore, a process referred to as tripping, and replaced, which increases costly rig time.

Often, this will result in a dune forming above the BHA or its larger components, which can build up to a size which increases the tension that must be applied to the drillstring to pull the BHA out of the hole, and in extreme cases blocks the hole impeding further progress of the drillstring out of the hole.

In order to avoid problems in removing the drillstring from the hole, and also re-entering drilled hole, extra time must be taken, for instance by pumping and rotating while pulling out, which can also have detrimental effects on hole quality due to rotational impacts of the bit and BHA with the borehole wall.

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