This invention relates to universal joints for drill string.
Universal joints transmit torque where there can be misalignment of two components. In a drilling operation, a drill bit is mounted to the end of a drill string. The drill string is rotated from the top of the string or by a motor at the bottom of the string, or both, to rotate the drill bit and advance the borehole. Universal joints are included in the drill string to accommodate eccentricity in the string. The eccentric rotation is converted into axial rotation in order for the drill bit to advance the borehole efficiently. Eccentricity may be initiated by a motor in the drive assembly that rotates the drill bit or by steering of the bit to change direction of the borehole or other operating conditions.
Mud motors are often used at the lower end of the drill string to rotate the bit. The motors have a rotor in a housing that rotates in response to the flow of drilling fluid. Universal joints are generally used to link the motor to the drill bit and convert eccentric rotation of the mud motor shaft to axial rotation. The constant relative movement of the components of the universal joint, in abrasive drilling mud, causes abrasion and erosion of mating components and can limit operational life of drill string components.
The present invention pertains to the use of gears in a downhole universal joint. In our embodiment, the gears are used to connect a mud motor to a drill bit. In one construction, a planetary gear assembly is used as part of a downhole drill string. The assembly functions as a universal joint to transmit torque between adjacent rotating components with shafts that may be not completely aligned. The assembly uses a planetary gear system to convert eccentric rotation to axial rotation. The gears can engage adjacent gears with corresponding teeth or can use magnetic force or friction between adjacent gears to transmit torque. A planetary gear system can provide a compact assembly that allows the components of the drill string to be positioned closer together shortening the drill string.
In one aspect of the present invention, a universal joint assembly for downhole applications includes a ring gear engaging a planetary gear to rotate a sun gear about a longitudinal axis. The assembly connects to components or tools of a drill string to transmit torque.
In another aspect of the invention, a driven gear with eccentric rotation drives a central gear with axial rotation connected to a downhole tool for advancing a borehole.
In another aspect of an embodiment of the invention, the gears engage each other by teeth on the rim of one gear. In another embodiment of the invention the gears engage each other by magnetic force. In another embodiment of the invention the assembly includes a flaccid line. In another embodiment of the invention the assembly includes a flex disc. In another embodiment of the invention the planetary gears are used in conjunction with a positive displacement motor or a rotational impulse tool.
A drill string in its basic form consists of sections of threaded pipe assembled end to end with a drill bit at a distal end for advancing a borehole. The drill string can be miles long and rotated at a proximal end of the pipe by a drilling rig to turn the drill bit and advance the borehole, Many kinds of tools can be included in the drill string to perform functions such as reaming out obstructions from the bore hole, vibrating the drill string, applying percussion to the bit, widening the borehole and rotating the drill bit.
In one example, a positive displacement motor or mud motor (PDM) can be installed near the drill bit to drive the drill bit instead of, or in addition to, driving the drill string from the above ground drill rig. Fluid is pumped down the drill string under pressure during operation to flush material out of the borehole. A mud motor uses the pressure of the fluid to drive the motor rotating an output shaft. The output of the motor is eccentric, with the output shaft rotating about a circle as well as rotating about the rotor axis. In order to limit the stress on the drill string and bit, this extraneous motion is converted to axial rotation.
The assembly of the present invention is shown in
The disclosed planetary gear assembly 10 includes a ring gear 12 fixed in relation to drill string 6, a sun or central gear 14 that rotates about a longitudinal axis LA1, and a planetary or medial gear 16 that engages the ring gear and sun gear. The planetary gear rotates about its own axis LA2 and also rotates eccentrically about the axis LA1. The planetary gear 16 is driven by shaft 18 mounted to the planetary gear. The sun gear has a shaft 20 mounted at its axis. Planetary gear systems are well known and understood by those skilled in the art.
In a typical downhole application, a mud motor 22 in a drill string is used to drive a bit 8. The mud motor includes a stator housing 22A fixed in relation to the drill string 6. Drilling fluid pumped down the drill string drives a rotor 22B in the stator. The stator generally has an offset rotation.
Shaft 18 is connected to rotor 22B. As a result shaft 18 rotates generally about its axis R1. The shaft rotates simultaneously about the axis LA1 in eccentric rotation or nutation. The actual motion of the drive shaft can include more complex motion in response to rotation of the rotor in the stator. The shaft 18 drives rotation of the planetary gear 16 by engagement of gear 16 with gear 12. Planetary gear 16 also rotates about its own axis and about axis LA1 similar to the drive shaft 18. The rotation of the planetary gear 16 in the fixed ring gear 12, while engaging the ring gear and the sun gear, drives the sun gear 14 to rotate. The planetary gear system 10 converts the eccentric rotation of the mud motor 22 and shaft 18 to axial rotation to drive the sun gear 14. Rotation of sun gear 14 drives shaft 20 and bit 8.
The planetary gear can be configured to drive a downstream tool at a higher speed or a lower speed than the rotational speed of rotor 228. Where sun gear 14 is smaller than planetary gear 16, the shaft 20 will rotate at a greater speed than shaft 18. Where sun gear 14 is larger than planetary gear 16, the shaft 20 will rotate at a slower speed than shaft 18. The teeth of each of the gears are of corresponding size to mesh efficiently. Gear size may be defined by the number of teeth on the gear. In some embodiments, the planetary gear assembly includes the sun gear and planetary gear, and the ring gear is omitted.
The sun gear, planetary gear and ring gear in some embodiments will be coplanar with the axes of each gear parallel. The shaft 18 can exhibit a complex motion coinciding with the rotation of the rotor 22B. As shown in in
To accommodate this cyclic stress, planetary gear 16 can incorporate a flex disc. A flex disc can be made from one or more discs of metal, plastic or other flexible material. The shaft 18 can be fixed to the center of the disc and the edges of the disc are attached to the planetary gear. Alternatively, the shaft terminates in a set of arms and the disc has a central opening. Each arm is attached to the disc at radially spaced positions. Angular misalignment of the shaft and the gear is accommodated by flexing of the disc between the mount of the shaft and the gear body (
In another embodiment, the shaft is flexible and can be a flaccid line or cable 18A (
In another embodiment, the planetary gear maintains a perpendicular orientation to shaft 18 and the gear is not limited to rotation in the plane of the sun gear 14 and ring gear 12.
Each of the gears can include teeth to engage the adjacent gear. Alternatively, the assembly can be configured without teeth. In such an embodiment, the gears exert adequate normal force on the adjacent gear so that friction limits slipping between the joining faces. The gear interfaces can incorporate resilient materials so the high normal force at the interfaces deflects the material and increases the surface area of the interface.
Alternatively, the gears can incorporate magnets in lieu of (or in addition to) teeth. Magnets placed at the edge of the gear can be oriented with alternating positive and negative poles around the edge of the gear as shown in
The planetary gear assembly 10 can include a service life indicator 26 (SLI) that displays a gauge of remaining service life for the component. The indicator can allow the operator to replace the universal joint before a downhole failure. Maters repeatedly flexed are subject to fatigue failure from hardening and can fracture. Contacting surfaces can wear and erode. In one embodiment, the service life indicator is a fatigue indicator. The fatigue indicator can be integrated with shaft 18. The fatigue indicator could be a strand or a coating incorporated with the shaft that flexes with the shaft in operation. The fatigue indicator 26A has a configuration or is a material selected to be more vulnerable to fatigue stress than the shaft.
For example, the fatigue indicator strand can be selected to have a service life 80% of the life of the shaft or cable. Reduced service life of the fatigue indicator may be a factor of the dimensions of the indicator, accelerated work hardening of the material or a harder material as compared to the balance of the shaft. At 80% of the service life, the wear indicator develops visible failure mechanisms such as thinning, cracking or other visible indicia that can be detected by the operator. The assembly can be removed from service in response to visual inspection of the fatigue indicator before the shaft fails.
Components of a drill string can be in contact with suspended particles of the drilling fluid that are abrasive and erode the components. In one embodiment, the service life indicator 26 is a wear or erosion indicator. The wear indicator can include a material layer 26B included on a gear. Erosion of the material layer to a critical thickness can be visually detected by the operator.
In some embodiments the service life indicator is inspected with a visual magnification, specific illumination such as ultraviolet light, ultrasonic testing, penetrant dye testing or other inspection methods. In some embodiments the service life indicator is a sensor that generates an electronic signal.
The planetary gear described here performs many of the functions of a universal joint but can convert eccentric rotation more efficiently to axial rotation and is more compact allowing a shorter working end of a drill string with better capability for steering the bit in the borehole than a conventional universal joint.
It should be appreciated that although selected embodiments of the representative planetary gear assemblies are disclosed herein, numerous variations of these embodiments may be envisioned by one of ordinary skill that do not deviate from the scope of the present disclosure. The disclosure set forth herein encompasses multiple distinct inventions with independent utility. The various features of the invention described above are preferably included in each universal joint. Nevertheless, the features can be used individually in a joint to obtain some benefits of the invention. While each of these inventions has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. Each example defines an embodiment disclosed in the foregoing disclosure, but any one example does not necessarily encompass all features or combinations that may be eventually claimed.
Number | Name | Date | Kind |
---|---|---|---|
763127 | Tilden | Jun 1904 | A |
1261962 | Scott | Apr 1918 | A |
1314990 | Stockwell | Sep 1919 | A |
1324063 | Noel | Dec 1919 | A |
1355516 | Rodolphe | Oct 1920 | A |
1362646 | Stockwell | Dec 1920 | A |
1373393 | Langworthy | Mar 1921 | A |
1376504 | Behn | May 1921 | A |
1421072 | Emet | Jun 1922 | A |
1422339 | Church | Jul 1922 | A |
1460594 | Le Moon | Jul 1923 | A |
1479755 | Stokes | Jan 1924 | A |
1488291 | Schell | Mar 1924 | A |
1550458 | Schell | Aug 1925 | A |
1653995 | English | Dec 1927 | A |
1739756 | Granville | Dec 1929 | A |
2025825 | Louis | Dec 1935 | A |
2217969 | Schairer | Oct 1940 | A |
2301659 | Louis | Nov 1942 | A |
2319027 | Aker | May 1943 | A |
2491820 | Leibing et al. | Dec 1949 | A |
2647380 | Henry et al. | Aug 1953 | A |
3118159 | Kollmann | Jan 1964 | A |
3203285 | Schmidt | Aug 1965 | A |
3497083 | Anderson et al. | Feb 1970 | A |
3757879 | Wilder et al. | Sep 1973 | A |
3895502 | Schwarz | Jul 1975 | A |
4055966 | Fredericks | Nov 1977 | A |
4233820 | Driver | Nov 1980 | A |
4449956 | Ueno | May 1984 | A |
4706659 | Matthews et al. | Nov 1987 | A |
4947942 | Lightle et al. | Aug 1990 | A |
4982801 | Zitka et al. | Jan 1991 | A |
5000723 | Livingstone | Mar 1991 | A |
5019015 | Wasserfuhr | May 1991 | A |
5048622 | Ide | Sep 1991 | A |
5053687 | Merlet | Oct 1991 | A |
5651737 | Blanc | Jul 1997 | A |
5740699 | Ballantyne et al. | Apr 1998 | A |
6155349 | Robertson et al. | Dec 2000 | A |
6173794 | von Gynz-Rekowski | Jan 2001 | B1 |
6220372 | Cherry | Apr 2001 | B1 |
6415735 | Rogers | Jul 2002 | B1 |
6676526 | Poster | Jan 2004 | B1 |
6896473 | Schuler | May 2005 | B2 |
7004843 | Kerstetter | Feb 2006 | B1 |
7100238 | McCauley | Sep 2006 | B2 |
7367772 | Khajepour et al. | May 2008 | B2 |
7549467 | McDonald | Jun 2009 | B2 |
8123644 | Marumoto | Feb 2012 | B2 |
8251938 | Morcuende et al. | Aug 2012 | B1 |
8317628 | Overfelt | Nov 2012 | B2 |
8602127 | Hummes | Dec 2013 | B2 |
8714245 | Sihler | May 2014 | B2 |
20110129375 | Kotsonis | Jun 2011 | A1 |
20140027185 | Menger et al. | Jan 2014 | A1 |
20150075871 | Strittmatter | Mar 2015 | A1 |
20150129311 | Regener | May 2015 | A1 |
20160060970 | Pierre et al. | Mar 2016 | A1 |
20160341255 | Kummer et al. | Nov 2016 | A1 |
20160356319 | Chase et al. | Dec 2016 | A1 |
20170002871 | McMillan et al. | Jan 2017 | A1 |
20170081928 | Maw et al. | Mar 2017 | A1 |
20170328416 | Maw et al. | Nov 2017 | A1 |
20170370420 | Deen et al. | Dec 2017 | A1 |
Number | Date | Country |
---|---|---|
241255 | Feb 1946 | CH |
163221 | Sep 1905 | DE |
2730486 | Jan 1979 | DE |
0048564 | Mar 1982 | EP |
485872 | Feb 1918 | FR |
15259 | Aug 1890 | GB |
189619223 | Aug 1897 | GB |
2017930 | Aug 1994 | RU |
2526957 | Aug 2014 | RU |
700710 | Nov 1979 | SU |
Entry |
---|
Final Office Action received from the U.S. Patent and Trademark Office in U.S. Appl. No. 14/838,155, dated Jul. 5, 2017, 7 pages. |
Final Office Action received from the U.S. Patent and Trademark Office in U.S. Appl. No. 15/160,809, dated Aug. 30, 2017, 12 pages. |
International Search Report and Written Opinion received from the International Search Authority in Patent cooperation Treaty Application No. PCT/US2015/047387, dated Dec. 10, 2015, 8 pages. |
Non-Final Office Action received from the U.S. Patent and Trademark Office in U.S. Appl. No. 14/838,155, dated Feb. 17, 2017, 9 pages. |
Non-Final Office Action received from the U.S. Patent and Trademark Office in U.S. Appl. No. 15/160,809, dated Dec. 14, 2016, 18 pages. |
Non-Final Office Action received from the U.S. Patent and Trademark Office in U.S. Appl. No. 15/195,892, dated Oct. 6, 2017, 9 pages. |
Request for Continued Examination and Amendment filed with the U.S. Patent and Trademark Office in U.S. Appl. No. 14/838,155, dated Jan. 4, 2018, 9 pages. |
Response to Non-Final Office Action filed with the U.S. Patent and Trademark Office in U.S. Appl. No. 14/838,155, dated Jun. 9, 2017, 6 pages. |
Response to Non-Final Office Action filed with the U.S. Patent and Trademark Office in U.S. Appl. No. 15/160,809, dated Jun. 14, 2017, 17 pages. |
Response to Restriction Requirement filed with the U.S. Patent and Trademark Office in U.S. Appl. No. 14/838,155, dated Jan. 26, 2017, 1 page. |
Restriction Requirement received from the U.S. Patent and Trademark Office in U.S. Appl. No. 14/838,155, dated Oct. 26, 2016, 7 pages. |
Request for Continued Examination and Amendment filed with the U.S. Patent and Trademark Office in U.S. Appl. No. 15/160,809, dated Feb. 28, 2018, 14 pages. |
U.S. Appl. No. 15/160,809, “Final Office Action” dated Jan. 18, 2019, 30 pages. |
U.S. Appl. No. 15/160,809, “Non-Final Office Action” dated Mar. 21, 2018, 19 pages. |
U.S. Appl. No. 15/195,892, “Final Office Action” dated Jul. 12, 2018, 11 pages. |
U.S. Appl. No. 15/195,892, “Notice of Allowance” dated Feb. 13, 2019, 6 pages. |
U.S. Appl. No. 15/160,809 , “Non-Final Office Action”, dated May 10, 2019, 13 pages. |
U.S. Appl. No. 15/636,469 , “Non-Final Office Action”, dated May 20, 2019, 10 pages. |
Number | Date | Country | |
---|---|---|---|
20170023068 A1 | Jan 2017 | US |
Number | Date | Country | |
---|---|---|---|
62196630 | Jul 2015 | US |