Patent Application
20180119491
The present disclosure relates in general to downhole motors used for drilling oil, gas, and water wells, and relates in particular to drive systems incorporated into such downhole motors.
In drilling a wellbore into the earth, such as for the recovery of hydrocarbons or minerals from a subsurface formation, it is conventional practice to connect a drill bit to the lower end of an assembly of drill pipe sections connected end-to-end (commonly referred to as a “drill string”), and then to rotate the drill string so that the drill bit progresses downward into the earth to create the desired wellbore. In conventional vertical wellbore drilling operations, the drill string and bit are rotated by means of either a “rotary table” or a “top drive” associated with a drilling rig erected at the ground surface over the wellbore (or, in offshore drilling operations, on a seabed-supported drilling platform or a suitably adapted floating vessel).
During the drilling process, a drilling fluid (also called “drilling mud”, or simply “mud”) is pumped under pressure downward through the drill string, out the drill bit into the wellbore, and then upward back to the surface through the annular space between the drill string and the wellbore. The drilling fluid, which may be water-based or oil-based, carries wellbore cuttings to the surface, but can also perform other valuable functions, including enhancement of drill bit performance (e.g., by ejection of fluid under pressure through ports in the drill bit, creating mud jets that blast into and weaken the underlying formation in advance of the drill bit), drill bit cooling, and formation of a protective cake on the wellbore wall (to stabilize and seal the wellbore wall).
Particularly since the mid-1980s, it has become increasingly common and desirable in the oil and gas industry to use “directional drilling” techniques to drill horizontal and other non-vertical wellbores, to facilitate more efficient access to and production from larger regions of subsurface hydrocarbon-bearing formations than would be possible using only vertical wellbores. In directional drilling, specialized drill string components and “bottomhole assemblies” (BHAs) are used to induce, monitor, and control deviations in the path of the drill bit, so as to produce a wellbore of desired non-vertical configuration.
Directional drilling is typically carried out using a downhole motor (also called a “drilling motor” or “mud motor”) incorporated into the drill string immediately above the drill bit. A typical downhole motor assembly includes the following primary components (listed in sequence, from the top of the motor assembly):
Conventional downhole motor assemblies commonly include power sections incorporating either a “Moineau” drive system (i.e., a progressive cavity motor, comprising a positive displacement motor of well-known type, with a helically-vaned rotor eccentrically rotatable within a stator section) or a turbine-type drive system.
In one operational mode, a downhole motor may rotate the bit without concurrent rotation of the drill string; this is referred to as “slide drilling”. In another operational mode, the downhole motor may rotate the bit relative to the drill string in conjunction with rotation of the drill string by a top drive or rotary table.
In recent years, the available torque output of downhole motor power sections has continued to increase due to improved technologies and manufacturing capabilities, and is outpacing the torsional capacity of downhole motors. This trend appears likely to continue as increasingly higher torques are required for drilling through hard subsurface formation materials.
Such high torque requirements are straining the capabilities of conventional downhole motors, causing premature failures and unfavorable drilling conditions such as “stick slip” and “BHA whirl” (terms that will be familiar to persons skilled in the art). Due to the design characteristics of conventional drilling tools, increased reactive torque loads are being transferred through the drill string components, resulting in back-offs and fatigue failures.
For the foregoing reasons, there is a need for downhole motors that will allow the use of lower-torque conventional power sections to drill through hard subsurface materials while reducing the magnitude of reactive torque loads being transferred to the drill string.
In general terms, the present disclosure teaches embodiments of downhole motors in which intermittent rotational and/or axial impacts are applied to the bearing mandrel and, therefore, to the drill bit.
In a first embodiment of a downhole motor in accordance with this disclosure (which first embodiment will be referred to herein for convenience as an “impact driver motor”), the bearing mandrel is rotated relative to the other primary drill string components by the application of regular axial and rotational impacts to the bearing mandrel, so as to rotate the bearing mandrel and the drill bit relative to the drill string. The impact driver motor can be used either for slide drilling operations or in conjunction with rotation of the drill string.
A second embodiment of a downhole motor in accordance with this disclosure (which second embodiment will be referred to herein for convenience as a “torsional impact motor”) is particularly intended for enhancing drilling effectiveness and efficiency by a higher frequency of axial impacts being applied to the bearing mandrel to enhance drilling effectiveness while continuously rotating the bit with the drive shaft assembly. In certain variants of the torsional impact motor, the impacts applied to the bearing mandrel may include a rotational (i.e., torque) component, inducing relative rotation between the bearing mandrel and the drill string.
Accordingly, the present disclosure teaches a downhole motor that includes:
In alternative variants, the downhole motor may be configured such that both rotational and axial impact forces will be imparted to the bearing mandrel upon the release of kinetic energy stored in the kinetic energy storage means.
In one non-limiting variant of the downhole motor, the cam apparatus includes a cam ring that has a central opening, and the cam ring is mounted within the bore of the housing so as to be rotatable with the housing. The drive mandrel passes through the central opening in the cam ring such that the drive mandrel is axially movable relative to the cam ring and the cam ring is rotatable about the drive mandrel. A plurality of cam lobes are formed on an upper end of the cam ring, with uniform angular intervals between adjacent cam lobes. Each cam lobe has a cam profile that defines a lower flat section, which is contiguous with a ramp section, which is contiguous with an upper flat section, which is contiguous with an axial face, which is contiguous with the lower flat section of the next adjacent cam lobe.
The cam apparatus in this variant also includes a roller cage disposed above the cam ring and coaxial therewith. The roller cage is disposed around and fixed to drive mandrel such that the roller cage is rotatable with the drive mandrel. The roller cage includes a plurality of rollers corresponding to the cam lobes in terms of number and angular spacing, with the rollers being configured for rollable engagement with the cam profiles of the cam lobes.
The kinetic energy storage means may comprises a helical spring disposed within an annulus between the drive mandrel and the housing, with a lower end of the spring reacts against the roller cage and an upper end of the spring reacting against a shoulder formed in the bore of the housing. In alternative variants, the kinetic energy storage means may be provided in the form of a gas spring.
In some variants of the downhole motor, the impact adapter teeth and the drive mandrel teeth are completely disengaged when the drive mandrel is at its uppermost axial position. In other variants, the impact adapter teeth and the drive mandrel teeth are never completely disengaged.
Embodiments in accordance with the present disclosure will now be described with reference to the accompanying Figures, in which numerical references denote like parts, and in which:
Referring first to
In the illustrated variant, a balancing piston 40 is disposed within an annulus 25 between bearing mandrel 20 and bearing mandrel housing 30 for prevention of differential pressure across a rotating seal between bearing mandrel 20 and bearing mandrel housing 30. However, this is by way of illustration only; the above-described function of piston 40 could be accomplished by other means known to persons skilled in the art, and piston 40 or functionally-equivalent means are not essential elements of the broadest embodiments within the scope of this disclosure.
As best appreciated with reference to
Anvil adapter 110 is rotatable within an anvil adapter housing 115 (which forms part of the overall motor assembly housing, and is shown only in
Although the two anvil adapter teeth in the illustrated variant are of essentially identical configuration, they are denoted in
A drive mandrel is provided above and in coaxial alignment with anvil adapter 110. For purposes of describing the impact driver motor illustrated in
Hammer mandrel 120 is rotatable within a hammer mandrel housing 125 (which forms part of the overall motor assembly housing, and is shown only in
Although the two hammer mandrel teeth in the illustrated variant are of essentially identical configuration, they are denoted in
An upper cylindrical portion of hammer mandrel 120 passes through and is axially movable relative to a cam ring 130, which is mounted within the bore of the motor assembly housing so as to be rotatable therewith; hammer mandrel 120 therefore is rotatable relative to cam ring 130. The upper end of cam ring 130 is formed with a plurality of cam lobes 131 (corresponding to teeth 112 and 122 in number and angular spacing). In the illustrated variant, cam ring 130 has two cam lobes, which although of essentially identical configuration are denoted in
Above cam ring 130, a roller cage 140 is coaxially disposed around and fixed to hammer mandrel 120 so as to be rotatable therewith. Roller cage 140 includes a plurality of rollers 142 corresponding to cam lobes 131 in number and angular spacing, and configured for rollable engagement with the cam profiles of cam lobes 131. In the illustrated variant, roller cage 140 has two rollers, which although of essentially identical configuration are denoted in
Above roller cage 140, hammer mandrel 120 passes through a helical spring 150 disposed within an annulus 121 between hammer mandrel 120 and hammer mandrel housing 125. As best seen in
As best seen in
The operation of impact driver motor 100 can be best understood with reference to
As rotation of hammer mandrel 120 continues, and as seen in
Due to the continuing rotation of hammer mandrel 120, the side faces of the hammer mandrel teeth (122A, 122B) also impart lateral impact forces against the side faces of the next-adjacent anvil adapter teeth (i.e., 112B and 112A) as seen in
As rotation of the drive shaft (not shown) continues, the rollers (142A, 142B) again move up the cam ramp sections 132, as shown in
This application of regular impact forces to anvil adapter 110 occurs continuously as the drive shaft and hammer mandrel 120 rotate, with the number of impacts per rotation equaling the number of anvil adapter teeth 112 (and hammer mandrel teeth 122 and cam lobes 131). For each full rotation of the rotor, the bit will only rotate a percentage of a turn, and this will lessen the reactive torque transferred to the drill string.
Referring first to
As best appreciated with reference to
A drive mandrel 220 is provided above and in coaxial alignment with impact adapter 210. Drive mandrel 220 is rotatable within a drive mandrel housing 225 (shown only in
As seen in greater detail in
As seen in
Drive mandrel 220 is axially movable within drive mandrel housing 225 such that it can stroke axially relative to impact adapter 210. However, the assembly is configured such that drive mandrel 220 is never completely disengaged from impact adapter 210, and relative rotational movement between drive mandrel 220 and impact adapter 210 is limited to the angular twist between impact adapter teeth 212 and drive mandrel teeth 222.
An upper cylindrical portion of drive mandrel 220 passes through and is axially movable relative to a cam ring 230 which is mounted within the bore of the motor assembly housing so as to be rotatable therewith; drive mandrel 220 therefore is rotatable relative to cam ring 230. The upper end of cam ring 230 is formed with a plurality of cam lobes 231. In the illustrated variant, cam ring 230 has two cam lobes, which although of essentially identical configuration are denoted in
Above cam ring 230, a roller cage 240 is coaxially disposed around and fixed to drive mandrel 220 so as to be rotatable therewith. Roller cage 240 includes a plurality of rollers 242 corresponding to cam lobes 231 in number and angular spacing, and configured for rollable engagement with the cam profiles of cam lobes 231. In the illustrated variant, roller cage 240 has two rollers, which although of essentially identical configuration are denoted in
Above roller cage 240, drive mandrel 220 passes through a helical spring 250 disposed within an annulus 221 between drive mandrel 220 and drive mandrel housing 225. As best seen in
As best seen in
The operation of torsional impact motor 200 can be best understood with reference to
As rotation of drive mandrel 220 continues, and as seen in
At the same time, the angled side faces 226 of the drive mandrel teeth 222 impart lateral impact forces against the angled side faces 216 of the corresponding impact adapter teeth 212 as seen in
This application of intermittent impact forces to impact adapter 210 occurs continuously as the power section and drive mandrel 220 rotate, with the number of impacts per rotation equaling the number of cam lobes 231.
Unlike the operation of impact driver motor 100, where the bit turns only when hammer mandrel 120 is engaged with anvil adapter 110, the operation of torsional impact motor 200 is characterized by constant rotation of the bit, but with the effectiveness of the bit being augmented by the application of axial and torsional impacts to increase the rate of penetration (ROP).
The imparting of axial and torsional impacts and the provision within the motor assembly of an oscillating internal mass (comprising, in the case of impact driver motor 100, hammer mandrel 120, the drive shaft, and the rotor; or, in the case of torsional impact motor 200, drive mandrel 220, the drive shaft, and the rotor) have an operational effect analogous to placing a vibration-inducing tool (or an additional vibrating-inducing tool) in the BHA very close to the bit.
It is to be understood that the scope of the claims appended hereto should not be limited by the preferred embodiments described and illustrated herein, but should be given the broadest interpretation consistent with the description as a whole. It is also to be understood that the substitution of a variant of a claimed element or feature, without any substantial resultant change in functionality, will not constitute a departure from the scope of the disclosure. By way of only one non-limiting example, variant embodiments within the scope of the present disclosure could incorporate alternative known means for storing kinetic energy in substitution for helical spring 150 (or 250), such as, for example, a gas spring, with annulus 121 (or 221) being made substantially gas-tight and filled with a compressible gas.
In this patent document, any form of the word “comprise” is to be understood in its non-limiting sense to mean that any element following such word is included, but elements not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one such element.
Any use of any form of the terms “connect”, “engage”, “couple”, “attach”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the subject elements, and may also include indirect interaction between the elements such as through secondary or intermediary structure. Relational or relative terms (including but not limited to “horizontal”, “vertical”, “parallel”, and “perpendicular”) are not intended to denote or require absolute mathematical or geometrical precision. Accordingly, such terms are to be understood as denoting or requiring substantial precision only (e.g., “substantially horizontal”) unless the context clearly requires otherwise.
In this patent document, certain components of disclosed embodiments are described using adjectives such as “upper” and “lower”. These adjectives are used to establish a convenient frame of reference to facilitate explanation and to enhance the reader's understanding of spatial relationships and relative locations of the various elements and features of the components in question. The use of these adjectives is not to be interpreted as implying that they will be strictly applicable in all practical applications and usages of downhole motor assemblies in accordance with the present disclosure, or that such motor assemblies must be used in spatial orientations that are consistent with the strict meanings of these adjectives. For example, motor assemblies in accordance with the present disclosure may be used in drilling horizontal or angularly-oriented wellbores. For greater certainty, therefore, the adjectives “upper” and “lower”, when used herein with reference to disclosed motor assemblies and components thereof, should be understood in the sense of “toward the upper or lower end (as the case may be) of the drill string”, regardless of what the actual spatial orientation of the motor assembly and the drill string might be in a given practical usage.
Wherever used in this document, the terms “typical” and “typically” are to be interpreted in the sense of representative or common usage or practice, and are not to be understood as implying invariability or essentiality.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2016/000082 | 3/24/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62137863 | Mar 2015 | US |
