WO2018151718A1

WO2018151718A1 - Drill string stabilizer

Info

Publication number: WO2018151718A1
Application number: PCT/US2017/017920
Authority: WO
Inventors: Stephen Gerald SOUTHLAND
Original assignee: Chevron USA Inc
Current assignee: Chevron USA Inc
Priority date: 2017-02-15
Filing date: 2017-02-15
Publication date: 2018-08-23
Anticipated expiration: 2019-08-15

Abstract

A drill string stabilizer (30) with an asymmetric arrangement of parts. The asymmetric design of the gage pads (304) and the junk slots (302) can provide increased efficiency, decreased vibration, and decreased localized equivalent circulating density.

Description

DRILL STRING STABILIZER

TECHNICAL FIELD

[0001] The present disclosure relates generally to drill string stabilizers, and more specifically to a drill string stabilizer with an asymmetric or offset arrangement of parts which results in reduced vibration.

BACKGROUND

[0002] Subterranean wellbores commonly extend underground for large distances, for example, wellbores can extend for miles. A drill string stabilizer is used within a drill string to mechanically stabilize the string in the borehole in order to avoid unintentional sidetracking, prevent differential sticking, and to lower vibrations, for example. Stabilizers are used at intervals along the length of the drill string in order to stabilize the drill string relative to the borehole. Stabilizers are also commonly used in the bottom hole assembly close to the drill bit. Drilling fluid is pushed down the borehole through the center of the drill string and the center of the drill string stabilizers. Cuttings from the formation and used drilling fluid (referred to collectively as "mud") passes up through the borehole along the exterior of the drill string and the exterior of the drill string stabilizers to the surface. Since a drill string stabilizer must contact both the wall of the wellbore and the drill string, as the drill turns, mud is circulated back up and must go through openings along the outside of the drill string stabilizers (referred to collectively as "junk slot") in order to reach the surface.

[0003] Figs. 1 and 2 illustrate cross sections of commonly used drill string stabilizers which comprise symmetric junk slots 2 and symmetric gage pads 4. Fig. 1 shows a drill string stabilizer with a rounded junk slot 2. Fig. 2 shows a drill string stabilizer with a U shaped junk slot 2. A drill string stabilizer comprises a mandrel 6 with gage pads 4 extending therefrom. The exterior sides of the gage pads are positioned to contact the wall of the wellbore in order to stabilize the drill string within the wellbore. The junk slot 2 located between the gage pads 4 is an open space on the exterior of the drill string stabilizer that is bounded by the mandrel 6, the wellbore wall 10, and adjacent gage pads 4. The center of the drill string stabilizer is hollow, referred to here as the internal bore 8. [0004] The design of stabilizers has been static in the arts, as most of the focus in design of drilling components has been directed to drill bits and rotary steering systems. This disclosure describes new designs for drill string stabilizers which can reduce rotational drag, vibrations, fluid loss events, and localized equivalent circulating density, which can improve localized fluid flow efficiency. The designs reduce friction of the drilling fluid that moves through the junk slots within the drill string stabilizer.

SUMMARY

[0005] A general embodiment of the disclosure is a drill string stabilizer comprising a plurality of asymmetric gage pads and asymmetric junk slots between the asymmetric gage pads, wherein each asymmetric gage pad comprises a long side and a short side in the radial plane. In embodiments, the drill string stabilizer only has rounded corners. In embodiments, an angle where the short side intersects a tangent of an adjacent edge of the asymmetric gage pad outside the exterior circumference of the drill string stabilizer and away from a closest asymmetric junk slot is between 70-105 degrees when measured in the radial plane. In specific embodiments, the angle where the short side intersects the tangent of the edge of the adjacent asymmetric gage pad, is between 85-95 degrees. In embodiments of the disclosure, an angle where the long side intersects a tangent of an edge of the asymmetric gage pad outside an exterior circumference of the drill string stabilizer and away from a closest asymmetric junk slot, is between 30-60 degrees. In specific embodiments, the angle where the long side intersects the tangent of the edge of the adjacent asymmetric gage pad is between 40-50 degrees. In embodiments of the disclosure, at least a portion of the long side is linear or the long side could be fully rounded. A portion of the short side could be linear or the short side could be fully rounded. The asymmetric gage pads can spiral around at least a portion of the exterior of the stabilizer, or can be straight in the longitudinal axis. In embodiments of the disclosure, the drill string stabilizer comprises at least two asymmetric gage pads and at least two asymmetric junk slots. For example, the drill string stabilizer could comprise three asymmetric gage pads, four asymmetric gage pads, five asymmetric gage pads, six asymmetric gage pads, or seven asymmetric gage pads. In another embodiment, the asymmetric gage pads are offset by 6 degrees or less around the exterior of the drill string stabilizer with respect to each other adjacent gage pad in the radial plane. [0006] Another general embodiment of the disclosure is a drill string stabilizer comprising: a mandrel; a first drill string attachment on a first axial end and a second drill string attachment on a second axial end of the mandrel; a plurality of gage pads spiraling around at least a portion of a circumference of the mandrel; a plurality of junk slots, each junk slot disposed between a pair of gage pads, wherein a majority of one lateral side of a junk slot is at an angle that is within 10 degrees parallel to the closest radius of the mandrel and a majority of another lateral side of the junk slot is at a 30-60 degree angle to a radius of the mandrel which intersects with a gage edge of the adjacent gage pad when the angles are measured in the radial plane. The drill string stabilizer can also only have rounded corners. In some embodiments, at least a portion of one or both of the lateral sides are linear. In other embodiments, one or both of the lateral sides are circular. The drill string stabilizer can comprise at least two gage pads and at least two junk slots. For example, the drill string stabilizer can comprise three gage pads and three junk slots, four gage pads and four junk slots, five gage pads and five junk slots, six gage pads and six junk slots, seven gage pads and seven junk slots, and so forth. In another embodiment, the gage pads are offset by 6 degrees or less around the exterior of the mandrel with respect to each other adjacent gage pad in the radial plane.

[0007] An additional general embodiment of the disclosure is a drill system comprising: a drill string; a drill bit coupled to the drill string; and one or more drill string stabilizers coupled to the drill string, at least one of the one or more drill string stabilizers comprising asymmetric gage pads and asymmetric junk slots. Each asymmetric gage pad comprises a long side and a short side in the radial plane. In embodiments, the drill string stabilizer only has rounded corners. In embodiments, an angle where the short side intersects a tangent of an adjacent edge of the asymmetric gage pad outside the exterior circumference of the drill string stabilizer and away from a closest asymmetric junk slot is between 70-105 degrees when measured in the radial plane. In specific embodiments, the angle where the short side intersects the tangent of the edge of the adjacent asymmetric gage pad, is between 85-95 degrees. In embodiments of the disclosure, an angle where the long side intersects a tangent of an edge of the asymmetric gage pad outside an exterior circumference of the drill string stabilizer and away from a closest asymmetric junk slot, is between 30-60 degrees. In specific embodiments, the angle where the long side intersects the tangent of the edge of the adjacent asymmetric gage pad is between 40-50 degrees. In embodiments of the disclosure, at least a portion of the long side is linear or the long side could be fully rounded. A portion of the short side could be linear or the short side could be fully rounded. The asymmetric gage pads can spiral around at least a portion of the exterior of the stabilizer, or can be straight in the longitudinal axis. In embodiments of the disclosure, the drill string stabilizer comprises at least three asymmetric gage pads and at least three asymmetric junk slots. For example, the drill string stabilizer could comprise three asymmetric gage pads, four asymmetric gage pads, five asymmetric gage pads, six asymmetric gage pads, or seven asymmetric gage pads.

[0008] Another general embodiment of the disclosure is a drill string stabilizer comprising: at least three gage pads and at least three junk slots arranged circumferentially around the outside of the drill string stabilizer; wherein at least two of an angle between two radii passing through a like point in each adjacent gage pad is different, all angles add up to 360 degrees, and all angles are measured in the radial plane. In embodiments of the disclosure, the angles between each adjacent gage pad differs by less than 6 percent. In a specific embodiment, every angle between the radii passing through a like point in each adjacent gage pad is different. In some embodiments, the drill string stabilizer can comprise three junk slots and three gage pads, four junk slots and four gage pads, five junk slots and five gage pads, and so forth.

[0009] These and other aspects, objects, features, and embodiments will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings illustrate only example embodiments of methods, systems, and devices for drill string stabilizers and are therefore not to be considered limiting of its scope, as stabilizers may admit to other equally effective embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements.

[0011] Figure 1 illustrates a cross section of a prior art drill string stabilizer.

[0012] Figure 2 illustrates a cross section of another prior art drill string stabilizer.

[0013] Figure 3 illustrates a portion of a cross section of an embodiment of the drill string stabilizer. [0014] Figure 4 illustrates an exterior view of an embodiment of a drill string stabilizer. The interior of the drill string stabilizer is shown in dotted lines.

[0015] Figure 5 is the cross section of A-A from Fig. 4.

[0016] Figure 6 is a cross section of an embodiment of a drill string stabilizer which comprises five gage pads and five junk slots.

[0017] Figure 7 is an example embodiment of a drill string comprising two drill string stabilizers.

[0018] Figure 8 is a photograph of a drill string stabilizer of the disclosure.

[0019] Figure 9 is an example of another embodiment of a drill string stabilizer of the disclosure.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0020] The example embodiments discussed herein are directed to systems, apparatuses, and methods of using drill string stabilizers. While the examples of drill string stabilizers shown in the figures and described herein are directed to use in an oil and/ or gas wellbore, examples of the drill string stabilizers can also be used in other applications aside from oil and gas uses, such as in drilling water wells.

[0021] Example embodiments of drill string stabilizers of the disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments of drill string stabilizers are shown. The stabilizers may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the drill string stabilizers to those of ordinary skill in the art. Like, but not necessarily the same, elements in the various figures are denoted by like reference numerals for consistency.

[0022] Terms such as "first," "second," "end," "inner," "outer," "distal," and

"proximal" are used merely to distinguish one component (or part of a component or state of a component) from another. Such terms are not meant to denote a preference or a particular orientation. Also, the names given to various components described herein are descriptive of one embodiment and are not meant to be limiting in any way. Those of ordinary skill in the art will appreciate that a feature and/or component shown and/or described in one embodiment (e.g., in a figure) herein can be used in another embodiment (e.g., in any other figure) herein, even if not expressly shown and/or described in such other embodiment. "About," and "substantially," as used herein prior to a number, refers to an amount that is within 3 percent of the number listed. A "plurality," as used herein, refers to two or more.

[0023] "Junk slot," as used herein, refers to the area between the mandrel, two gage pads, and the external circumference of the drill string stabilizer. The exterior circumference of the drill string stabilizer is a circle defined by the wellbore facing outer side of the gage pads and is adjacent the wellbore wall when the drill string stabilizer is downhole. Junk slots run uninterrupted from one longitudinal end of the drill string to the other longitudinal end, allowing for the passage of material through the outside of the drill string stabilizer when located in a borehole.

[0024] "Asymmetric drill string stabilizer" as used herein, refers to a drill string stabilizer with asymmetric gage pads and asymmetric junk slots.

[0025] "Mandrel," as used herein, refers to the area between the circumference of the drill string stabilizer internal bore 8 wall and the circumference where the junk slot starts. That is, the mandrel refers to a solid ring around the internal bore 8, which does not include any open areas.

[0026] "Gage pad," as used herein, refers to the projections extending from the mandrel of the drill string stabilizer. The gage pads may be integral to the mandrel, that is, the gage pads are formed of the same material as the mandrel or the gage pads may be discrete components attached to the mandrel.

The "internal bore," as used herein, refers to the hole running through the center of the drill string, the drill string stabilizer, and the drill bit connecting one longitudinal side to the other. The internal bore is different from the "borehole" or "wellbore" which refers to the well itself.

[0027] "Short side" is the shortest side of a gage pad running from mandrel circumference to exterior circumference in the radial plane. The short side is also the shortest side of an adjacent junk slot. If a portion of the short side is straight, the direction of the "short side" for angle measuring purposes is defined herein as a line that comprises the shortest distance between the mandrel circumference and the exterior circumference which runs through the most points of the short side in the radial plane. If the entire short side is curved, the direction of the short side for angle measurement purposes is defined herein as a line intersecting the mandrel circumference and the exterior circumference which is also tangent to the short side at the point the short side meets the gage pad edge prior to rounding.

[0028] "Long side" is the longest side of a gage pad running from mandrel circumference to exterior circumference in the radial plane. The long side is also the longest side of an adjacent junk slot. If a portion of the long side is straight, the direction of the "long side" for angle measurement purposes is defined herein as a line that comprises the shortest distance between the mandrel circumference and the exterior circumference which runs through the most points on the long side in the radial plane. If the entire long side is curved, the direction of the long side for angle measurement purposes is defined herein as a line intersecting the mandrel circumference and the exterior circumference which is also tangent to the long side at the point the long side meets the gage pad edge prior to rounding.

[0029] "Radial plane," as used herein, refers to the plane that is perpendicular to the longitudinal axis of a drill string stabilizer.

[0030] "Offset," as used herein, refers to positioning of a plurality of elements around a circle that is slightly off symmetric. For example, the positions of the elements can be offset by less than 6 degrees. For example, three elements positioned offset around a circle could position the elements at 118°, 120°, and 122° around the outside of the circle.

[0031] Fig. 3 provides a partial view of a cross section of a drill string stabilizer 30 of the disclosure which comprises asymmetric junk slots 302 and asymmetric gage pads 304. The asymmetric junk slot 302 is bounded by two adjacent asymmetric gage pads 304, the mandrel circumference 306, and the exterior circumference 308 of the drill string stabilizer 30. The asymmetric gage pad 304 is bounded by the mandrel circumference 306, the asymmetric junk slot 302, and the exterior circumference 308. The lateral sides of each asymmetric gage pad 304 on the asymmetric junk slot 302 sides comprise a short side 310 and a long side 312, wherein the length of the short side 310 is less than the length of the long side 312. The wellbore facing gage pad side 324 of the asymmetric gage pad 304 meets the lateral sides of the asymmetric gage pad at a gage pad edges 326.

[0032] Length measurements of each lateral side (short side 310 and long side

312) of the gage pad are taken in the radial plane 314 and measured from the point at which the lateral side of the gage pad meets the mandrel circumference 306 to the point at which the lateral side of the gage pad meets the exterior circumference 308 at the gage pad edge 326 (taken prior to the gage pad edges being rounded off). The length of each lateral side of the asymmetric junk slot 302 are equal to the length of the corresponding lateral side of the asymmetric gage pad 304. That is, the length of the short side 310 of an asymmetric junk slot 302 is equal to the length of the short side 310 of the adjacent asymmetric gage pad 304. The length of the long side 312 of the junk slot is equal to the length of the long side 312 of the adjacent asymmetric gage pad 304. Additionally, the wellbore facing gage pad side 324 can comprise stabilizer pads. The stabilizer pads can comprise wear elements and/or a wear resistant coating. The stabilizer pads can be ground smooth and flush as to minimize rotational friction.

[0033] In embodiments of the disclosure, the angle between where the short side

310 intersects the tangent of the exterior circumference 308 at a gage pad edge 326 (outside the exterior circumference 308 and away from the closest junk slot 302, the angle shown as 316) can be between 75-105 degrees, for example, and in other examples can be between 85-95 degrees, 87-93 degrees, 88-92 degrees, 89-91 degrees, or at 90 degrees. In embodiments of the disclosure, the angle between where the long side 312 intersects the tangent of the exterior circumference 308 at the gage pad edge 326 (outside the exterior circumference 308 and away from the closest junk slot 302, the angle shown as 318) can be between 30-60 degrees, for example, and in other examples can be between 40-50 degrees, 42-48 degrees, 43-47 degrees, 44-46 degrees, or at 45 degrees. The angle measurements are taken in the radial plane.

[0034] The angles at which the short and long sides intersect the wellbore facing gage pad side 324 can be determined using various methods and basic geometric principles. For example, the angle across tangent line 330 from angle 316, which is mostly contained within the asymmetric gage pad 304, would be equal to 180 minus the degrees of angle 316. The angles could also be measured against a radius of the drill string stabilizer 30. For example, one lateral side of a junk slot 302, the short side 330, could be at an angle that is within 10 degrees parallel to a radius of the drill string stabilizer 332 that intersects with a gage pad edge 326 of the adjacent asymmetric gage pad 304 and the other lateral side of the junk slot, the long side 312, could be at a 30-60 degree angle to a radius of the drill string stabilizer 30 which intersects with a gage pad edge 326 of the adjacent asymmetric gage pad 304. The angle measurements determined from a radius as described in this paragraph are substantially equivalent to the angle measurements described in the preceding paragraph that use a tangent to the exterior circumference 308.

[0035] In certain embodiments, the corner of the intersection is rounded on one or both of the short side 310 and the long side 312. In embodiments of the disclosure, angle measurements are taken discounting rounded edges.

[0036] In certain embodiments of the disclosure at least a portion of the long side

312 is linear, whereas the remainder can have a curvature. In certain embodiments, greater than 15 percent of the long side 312 is linear, for example, and in other examples the long side 312 could be between 15-98 percent linear, 20-95 percent linear, 30-80 percent linear, 40-70 percent linear, or 50-60 percent linear. In certain embodiments of the disclosure, the majority of the long side 312 is linear.

[0037] In embodiments of the disclosure at least a portion of the short side 310 is linear, whereas the remainder can have a curvature. In certain embodiments, greater than 15 percent of the short side 310 is linear, for example, and in other examples the short side 310 could be between 15-98 percent linear, 20-95 percent linear, 30-80 percent linear, 40- 70 percent linear, or 50-60 percent linear. In certain embodiments of the disclosure, the majority of the short side 310 is linear, whereas in other embodiments the majority of the short side 310 is curved.

[0038] In embodiments of the disclosure the bottom of the asymmetric junk slot

320 is rounded. For example, the bottom of the asymmetric junk slot 320 can follow the radius of an imaginary circumference, such as the bottom junk slot circle 322 shown in Fig. 3. The diameter of the bottom junk slot circle 322 can be shorter, equal to, or longer than the shortest distance between the mandrel circumference 306 and the exterior circumference 308. The bottom of the junk slot 320 may also be curved in the other direction, for example by following along the rounded line of the mandrel circumference 306.

[0039] In embodiments of the disclosure, the percent of the wellbore facing side

324 of the gage pad 304 takes up 30-70 percent of the exterior circumference 308, while the void from the junk slot 302 takes up the remainder of the exterior circumference 308. In embodiments of the disclosure, the percent of the wellbore facing side of the gage pad 324 takes up 50-65 percent of the exterior circumference 308, while the void from the junk slot takes up the rest. The design of the cross-sectional area of the asymmetric gage pad 304 may be dependent on the type of rock within a well to be drilled. For example, use of the drill string stabilizer 30 with a softer rock may call for the wellbore facing gage pad side 324 to make up a larger percent of the total exterior circumference 308, while working with a harder rock may require the wellbore facing gage pad side 324 to constitute a smaller percent of the total exterior circumference 308. In certain embodiments of the disclosure, the cross-sectional area of the asymmetric junk slot 302 is between 7-50 percent of the cross-sectional area inside the exterior circumference 308. In specific embodiments the junk slot cross-sectional area is between about 40 and about 50 percent of the cross-sectional area inside the exterior circumference 308. The drill string stabilizer 30 may be of any diameter used to drill a well.

[0040] Fig. 4 illustrates a side view of a drill string stabilizer 30 of the disclosure.

The drill string stabilizer 30 comprises a hollow mandrel 6 with asymmetric gage pads 304 that protrude therefrom. Asymmetric junk slots 302 are formed between the asymmetric gage pads 304. The asymmetric junk slots 302 run along the entirety of the asymmetric gage pads 304 such that they form an open corridor connecting both longitudinal ends of the drill string stabilizer 30. The internal bore 8 runs through the entirety of the drill string stabilizer 30. Both longitudinal ends of the drill string stabilizer 30 comprises drill string connectors 402 that can attach and detach from a drill string. For example, the drill string connectors 402 can be threading, clips, or the like. The drill string connectors 402 can be of the same type or of different types. Longitudinal axis 404, as used herein, refers to the axis that runs longitudinally along the drill string stabilizer 30. In embodiments, the drill string stabilizer 30 has all rounded edges. The string stabilizer 30 may be a near bit stabilizer or a string stabilizer. The string stabilizer 30 may be made of one piece of material, such as metal, or may be an assembly of multiple components. In embodiments of the disclosure, the long side 312 of the asymmetric gage pad 304 is positioned such that it follows as the trailing edge of the junk slot when the drill string stabilizer 30 is rotating.

[0041] Fig. 5 illustrates the cross section of the drill string stabilizer 30 of Fig. 4 at the cross section labeled A-A. As illustrated, the drill string stabilizer 30 comprises three asymmetric junk slots 302, three asymmetric gage pads 304, an internal bore 8, and a mandrel 6. Additionally, in embodiments of the disclosure, the bottom of the junk slot 320 runs along the mandrel circumference 306. When drilling smaller holes with smaller drills, maintaining a larger area of mandrel 6 while still increasing the area of the junk slot maintains the structural integrity of the drill string stabilizer 30, while still reducing vibration and reducing localized equivalent circulating density. [0042] Fig. 6 illustrates another example configuration of the drill string stabilizer

30 which includes five asymmetric gage pads 304 and five asymmetric junk slots 302. Embodiments of the disclosure include drill string stabilizers 30 with two or more asymmetric gage pads 304, such as three, four, five, six, or seven asymmetric gage pads 304. Embodiments of the disclosure include an equal number of asymmetric junk slots 302 per asymmetric gage pads 304, for example, three, four, five, six, or seven asymmetric junk slots 302.

[0043] Fig. 7 illustrates an example embodiment of a drill string system comprising two drill string stabilizers 30 with asymmetric gage pads 304 and asymmetric junk slots 302. The drill string 712 comprises a drill string stabilizer in middle of the wellbore 704 and a near bit drill string stabilizer 30 within the bottom hole assembly 706. The bottom hole assembly 706 comprises a drill bit 708, drill sub-assemblies 710, and a drill string stabilizer 30.

[0044] In some embodiments of the disclosure, the drill string stabilizer 30 is part of a bottom hole assembly 706. For example, the drill string stabilizer 30 could be adjacent to the drill bit 708. In other embodiments of the disclosure the drill string stabilizer 30 is not part of the bottom hole assembly 706, and instead resides along the length of the drill string 712. In some embodiments, a drill string 712 can comprises one or more drill string stabilizers 30. For example, a drill string 712 could comprises three drill string stabilizers 30 spaced along the length of the drill string 712 and a drill string stabilizer 30 as part of the bottom hole assembly.

[0045] Fig. 8 is a photograph of a drill string stabilizer 30 with asymmetric gage pads 304 and asymmetric junk slots 302. The long side 312 and the short side 310 of the asymmetric gage pads 304 and junk slots 302 are highlighted with dashed lines showing the edges and degrees of contact.

[0046] Fig. 9 is an example of another embodiment of a drill string stabilizer with radially offset gage pads 90. The drill string stabilizer with radially offset gage pads 90 has three gage pads 4 and three junk slots 2. The gage pads 2 are offset, such that the angles between the radius (on the radial plane) of the stabilizer through each adjacent gage pad 4 at a like point within the gage pads 4, is different. As shown, the like point is the middle of the gage pads. The like location or like point within a gage pad could be the leading edge of the gage pads, the trailing edge of the gage pad, or the middle of the gage pad, for example. In some embodiments, the difference between the angles is less than 6 degrees. For example, Fig. 9 shows the angles between each radius as 118°, 120°, and 122°. The angles between all of the gage pads must add up to 360°.

[0047] In embodiments, the drill string stabilizer with offset gage pads 90 comprises more than three gage pads 4. For example, the drill string stabilizer with offset gage pads 90 could comprises four gage pads, five gage pads, or six gage pads. In each case, the angles between at least two radii of the stabilizer 90 through each adjacent gage pad 4 at like points in the gage pad 4 are different. In a specific embodiment, all of the angles between the radius of the stabilizer 90 and each adjacent gage pad 4 are different. The angles must add up to 360° as they are taken in the radial plane.

[0048] In embodiments, the width of the gage pad and/or the width of the junk slots is varied in order to compensate for the arrangement of the offset gage pads. For example, the junk slots could be kept the same constant geometry within a drill string stabilizer with offset gage pads 90 as it would have a standard non-offset symmetric configuration and, instead, the width of the gage could be varied to compensate for the offset position.

[0049] In embodiments of the disclosure, the drill string stabilizer with offset gage pads 90 has standard symmetric junk slots as shown in Fig. 9. In other embodiments of the disclosure, the drill string stabilizer has asymmetric junk slots 302 and asymmetric gage pads 304 as described previously.

[0050] Example embodiments reduce the amount of vibration and/or increase localized equivalent circulating density. Reducing the amount of vibration within a drill string allows for reduced down time and more efficient operation of a drill string. Specifically, by reducing vibrations less trips need to be taken down hole to replace sensitive hi-technology electronic tools that may prematurely fail due to vibration and will also increase drilling efficiency as the drilling energy applied is used more efficiently in the absence of vibration.

[0051] Although embodiments described herein are made with reference to example embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope and spirit of this disclosure. Those skilled in the art will appreciate that the example embodiments described herein are not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the example embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments using the present disclosure will suggest themselves to practitioners of the art. Therefore, the scope of the example embodiments is not limited herein.

Example

[0052] A field study was performed to compare symmetric drill string stabilizers to the drill string stabilizers with asymmetric junk slots. Two wells were drilled within the same fault block. One with a symmetric drill string stabilizer and one with a drill string stabilizer with asymmetric junk slots (referred to as an asymmetric string stabilizer within this example). The asymmetric string stabilizers used in the comparison did not have the edges of the gage pad rounded prior to deployment. The junk slot area in the asymmetric string stabilizer had 10% more cross-sectional area than the junk slot in the symmetric string stabilizer. All other parts within the drill string were standard between the two well tests. The asymmetric drill string stabilizers showed a significant reduction of vibration. Within one two well block comparison, using the asymmetric drill string stabilizer resulted in a 30% reduction in torsional vibration severity and a 30% reduction in torsional vibration duration in comparison to the symmetric drill string stabilizer. In a second block comparison between two wells, using the asymmetric drill string stabilizer resulted in a 30%) less torsional vibration severity and a 30%> less torsional vibration duration in comparison to the symmetric drill string stabilizer

Claims

CLAIMS What is claimed is:

1. A drill string stabilizer comprising a plurality of asymmetric gage pads and

asymmetric junk slots between the plurality of asymmetric gage pads, wherein each asymmetric gage pad comprises a long side and a short side in the radial plane.

2. The drill string stabilizer of claim 1, wherein the drill string stabilizer only has rounded corners.

3. The drill string stabilizer of claim 1, wherein an angle where the short side

intersects a tangent at an edge of the adjacent asymmetric gage pad is between 70- 105 degrees when measured in the radial plane, the angle being outside an exterior circumference of the drill string stabilizer and away from a closest asymmetric junk slot.

4. The drill string stabilizer of claim 3, wherein the angle where the short side

intersects the tangent of the edge of the adjacent asymmetric gage pad is between 85-95 degrees.

5. The drill string stabilizer of claim 1, wherein an angle where the long side

intersects a tangent at an edge of the adjacent asymmetric gage pad is between 30- 60 degrees, the angle being outside an exterior circumference of the drill string stabilizer and away from a closest asymmetric junk slot.

6. The drill string stabilizer of claim 5, wherein the angle where the long side

intersects the tangent of the edge of the adjacent asymmetric gage pad is between 40-50 degrees.

7. The drill string stabilizer of claim 1, wherein at least a portion of the long side is linear.

8. The drill sting stabilizer of claim 1, wherein the short side is fully rounded.

9. The drill string stabilizer of claim 1, wherein the asymmetric gage pads spiral around at least a portion of the exterior of the stabilizer.

10. The drill string stabilizer of claim 1, wherein there are three asymmetric gage pads and three asymmetric junk slots.

11. The drill string stabilizer of claim 1, wherein there are five asymmetric gage pads and five asymmetric junk slots.

12. The drill string stabilizer of claim 1, wherein the asymmetric gage pads are offset by 6 degrees or less around the exterior of the drill string stabilizer with respect to each other adjacent gage pad in the radial plane.

13. A drill string stabilizer comprising:

a mandrel;

a first drill string attachment on a first axial end and a second drill string attachment on a second axial end of the mandrel;

a plurality of gage pads spiraling around at least a portion of a circumference of the mandrel;

a plurality of junk slots, each junk slot disposed between a pair of gage pads, wherein a majority of one lateral side of a junk slot is at an angle that is within 10 degrees parallel to the closest radius of the mandrel and a majority of another lateral side of the junk slot is at a 30-60 degree angle to a radius of the mandrel which intersects with a gage edge of the adjacent gage pad when the angles are measured in the radial plane.

14. The drill string stabilizer of claim 13, wherein the drill string stabilizer only has rounded corners.

15. The drill string stabilizer of claim 13, wherein at least a portion of the each lateral side is linear.

16. The drill string stabilizer of claim 13, wherein the drill string stabilizer comprises three gage pads and three junk slots.

17. The drill string stabilizer of claim 13, wherein the drill string stabilizer comprises five gage pads and five junk slots.

18. The drill string stabilizer of claim 13, wherein the gage pads are offset by 6

degrees or less around the exterior of the mandrel with respect to each other adjacent gage pad in the radial plane.

19. A drill system comprising:

a drill string; a drill bit coupled to the drill string; and

one or more drill string stabilizers coupled to the drill string, at least one of the one or more drill string stabilizers comprising asymmetric gage pads and asymmetric junk slots.

20. A drill string stabilizer comprising:

at least two gage pads and at least two junk slots arranged circumferentially around the outside of the drill string stabilizer; wherein

at least two of an angle between two radii of the drill string stabilizer passing through a like point in each adjacent gage pad is different,

all angles add up to 360 degrees, and

all angles are measured in the radial plane.

21. The drill string stabilizer of claim 20, wherein the angles between each adjacent gage pad differ by less than 6 percent.

22. The drill string stabilizer of claim 20, wherein every angle between the radii

passing through a like point in each adjacent gage pad is different.

23. The drill string stabilizer of claim 20, wherein the drill string stabilizer comprises three junk slots and three gage pads.

24. The drill string stabilizer of claim 20, wherein the like points through each adjacent gage pad is the leading edge.