High Annular Area Low Friction Stabilizer Design
A low friction stabilizer having a body and a plurality of small contact pads configured to function with the effectiveness of a single, larger contact pad is described. The assemblage and configuration of the small contact pads enable the performance of stabilization while reducing rotational drag and while allowing high annular flow around the stabilizer.
Embodiments usable within the scope of the present disclosure relate, generally, to drill string stabilizers configured within drill strings and used in earth boring operations, and in particular designs of stabilizers which reduce rotational drag and improve drilling fluid flow during operation.
BACKGROUND OF THE INVENTIONDrill string stabilizers are well-known in the field of oil and gas well drilling as a means to avoid unintentional destabilizing forces known to occur in drilling operations. Stabilizers are commonly used to reduce vibrations, sidetracking and other unwanted effects of drilling through geologic formations. The use of stabilizers, in addition, can aid in maintaining the orientation of the drill bit as well as the drill string during operation, reducing the possibility of drift.
Stabilizers operate by making physical contact with the interior wall of the borehole. Typically, stabilizers are constructed with one or more ribs, ridges, blades, or gage pads which protrude from the main body of the tool. These protuberances are placed in physical contact with the borehole wall, thereby providing stability. Contact, however, is made at the cost of rotational drag forces created between the protuberances and the borehole wall. Being placed in direct contact with the walls of the borehole, stabilizer protuberances must be constructed of durable materials. When used to stabilize the drill string within the borehole, protuberances are typically constructed from or with wear resistant materials. Rotational drag forces created by the contact of the protuberances with the borehole wall can lead to damage or fouling of the stabilizer. Further, vibration caused by these rotational drag forces can lead to breakage of some other parts of the drill string.
Stabilizers can be designed to hold the drill string in a fixed orientation or can be designed to allow orientational changes, such as are necessary in directional drilling. Variation of the length of the protuberances along the main body of the tool allows the drill string either to be held in a fixed position relative to direction, such as when longer protuberances are used, or to allow flexing of the drill string to allow orientation or reorientation of the drill string during directional drilling, such as when shorter protuberances are used.
Moreover, stabilizers must be constructed so as not to obstruct the flow of drilling fluid, which is pumped into the borehole in part to cause the removal of pieces of rock cut away from the geologic formation by the drill bit, thereby cleaning the borehole. An interstitial area is commonly placed between the protuberances, through which the drilling fluid is circulated, carrying rock cuttings and other debris with the drilling fluid. Such an interstitial area between two protuberances known in the art would be generally of the same shape as the protuberances. That is, if the protuberances are straight, the interstitial area will be straight lithe protuberances are curviform, the interstitial area between them will be curviform.
While stabilizers must, therefore, be designed to withstand the harsh conditions of the borehole during drilling operations, they must also be designed not to impede the flow of drilling fluid, which is equally necessary for effective drilling operations. Current stabilizer designs are typically seen either to contain large, straight protuberances, which allow the stabilizer to stand up against frictional forces, or stylized or curviform designs which reduce frictional forces but impede the flow of drilling fluid.
Specifically, current stabilizer designs are generally seen to contain large, straight protuberances designed for soft formations and maximum fluid flow or bypass area or they contain spiral-shaped or helical protuberances with larger contact surfaces to retain outer diameter and maximize centralization.
In typical stabilizer design, longer and wider protuberances, whether straight or curviform, improve stability but impede the passage of drilling fluid. Longer protuberances likewise typically reduce flexing of the drill string, while shorter protuberances allow more flexing. Protuberance length is determined by the need for directional drilling capabilities of the drill string. Longer and/or wider protuberances also increase rotational drag forces. Longer and wider protuberances, in reducing or impeding drilling fluid flow, can lead to cleaning issues or cause cuttings to foul or aggregate and pack off the fluid passage below the projections. At the same time, the constricted space between protuberances causes increased fluid speed between the protuberances, which may fluffier lead to erosion or abrasion of the protuberances caused by the impact of rock cuttings or other debris against the sides of the protuberances. Exemplary designs of stabilizers are found in U.S. Pat. No. 3,642,079, U.S. Pat. No. 5,330,016, and Chinese patent publication 201,635,674. These examples reflects designs in which stabilizer protuberances are curviform (the '079 patent), straight ('016) or a combination of straight and curviform design elements (the '674 patent).
There is a need for a stabilizer design which effectively moderates these requirements of sturdy design for longevity, a reduced frictional contact surface between the projections and the wall of the borehole, flexibility as to directional containment or directional reorientation, and protuberance design which does not impede or reduce the flow of drilling fluid circulating in the borehole.
The present invention incorporates design elements improving the performance characteristics of the stabilizer as to each of the above needs.
SUMMARY OF THE INVENTIONThe present invention optimizes stabilizer protuberances in the form of contact pad design to reduce friction, increase fluid flow between such stabilizer contact pads and allow variable flexure without compromising stabilizer strength. The stabilizer contact pads of this invention are based in part on curviform stabilizer pad design while allowing linear flow for drilling fluid axially along the body of the stabilizer. Instead of a single, elongate and curved stabilizer pad, the present invention uses a plurality of smaller contact pads assembled in the approximate shape of a single, curviform stabilizer pads but in which the assemblage of a plurality of contact pads results in a stabilizer pad with reduced surface area and improved flow characteristics.
In the detailed description of various embodiments of the present invention presented below, reference is made to the accompanying drawings, in which:
Before explaining selected embodiments of the present inventions in detail, it is to be understood that the present invention is not limited to the particular embodiments described herein and that the present invention can be practiced or carried out in various ways.
The shortcomings of the exemplary stabilizer design depicted in
As shown on
Robustness of the stabilizer depicted in
The layout of the plurality of contact pads 30 on
Further, in each of the embodiments illustrated on
The configuration of contact pads and junk slots illustrated on
The configuration as to contact pads 30, 40 and 50, and junk slots 31, 41, and 51 on
While various embodiments of the present inventions have been described with emphasis, it should be understood that within the scope of the appended claims, the present invention might be practiced other than as specifically described herein.
Claims
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2. (canceled)
3. (canceled)
4. (canceled)
5. A rotary drill string stabilizer for use in drilling a bore hole comprising:
- a tubular structure having means adapted to secure the structure in a bottom hole apparatus,
- an axial flow passageway formed through said stabilizer through which drilling fluid can flow toward the drill bit of the bottom hole apparatus;
- the tubular structure being smaller in diameter than the bore hole being drilled and on which are disposed a plurality of positioned contact pads,
- said plurality of positioned contact pads being in frictional contact with the inner diameter of the bore hole being drilled
- the plurality of said contact pads being positioned in a lesser plurality of intersticed circumferential helical blades along the tubular structure and further
- the placement of contact pads on the tubular structure resulting in linear junk slots through the intersticed circumferential helical blades.
6. The rotary drill string stabilizer of claim 5 in which the contact pads are disposed on the tubular structure pair-wise.
7. The rotary drill string stabilizer of claim 5 in which a smaller number of larger contact pads are disposed in a plurality of circumferential helical blades.
8. The rotary drill string stabilizer of claim 6 in which a larger number of smaller contact are disposed in a plurality of generally helical blades.
9. The rotary drill string stabilizer of claim 5 in which the intersticed contact pads create reduced frictional loss during operation.
10. The rotary drill string stabilizer of claim 6 in which the intersticed contact pads create reduced frictional loss during operation.
11. The rotary drill string stabilizer of claim 5 in which intersticed contact pads create a large annular junk slot volume.
12. The rotary drill string stabilizer of claim 6 in which the intersticed contact pads create a large annular junk slot volume.
13. The rotary drill string stabilizer of claim 5 in which a shorter length of the intersticed circumferential helical blades along the longitudinal axis of the tubular structure allows increased drill string flexibility.
14. The rotary drill string stabilizer of claim 5 in which a longer length of the intersticed circumferential helical blades along the longitudinal axis of the tubular structure allows decreased drill string flexibility.
15. The rotary drill string stabilizer of claim 6 in which a shorter length of the intersticed circumferential helical blades along the longitudinal axis of the tubular structure allows increased drill string flexibility.
16. The rotary drill string stabilizer of claim 6 in which a longer length of the intersticed circumferential blades along the longitudinal axis of the tubular structure allows decreased drill string flexibility.
17. A rotary drill string stabilizer comprising a tubular structure on which are disposed contact pads in a plurality of helical blades approximating the size and shape of a solid helical blades and in which
- junk slots are formed between the contact pads parallel to the longitudinal axis of the tubular structure, which junk slots are approximately linear along the longitudinal axis of the tubular structure.
18. The rotary drill string stabilizer of claim 17 in which a smaller number of larger contact pads are disposed in a plurality of circumferential helical blades.
19. The rotary drill string stabilizer of claim 17 in which a larger number of smaller contact pads are disposed in a plurality of circumferential helical blades.
20. The rotary drill string stabilizer of claim 17 in which the use of intersticed contact pads result in reduced frictional loss with no loss of drill string stability.
21. The rotary drill string stabilizer of claim 17 in which the intersticed contact pads create a large annular junk slot volume.
22. The rotary drill string stabilizer of claim 17 in which the contact pads are disposed on the tubular structure pair-wise.
23. A rotary drill string stabilizer for use in drilling a bore hole comprising:
- a tubular structure having means adapted to secure the structure in a bottom hole apparatus,
- the generally tubular structure being smaller in diameter than the bore hole being drilled and on which are disposed a plurality of positioned contact pads,
- said plurality of positioned contact pads being sufficiently radially sized to be in frictional contact with the inner diameter of the bore hole being drilled
- a sufficient number of said contact pads being positioned in a lesser plurality of intersticed circumferential helical blades along the tubular structure and further
- linear junk slots between contact pads which allow tripping of the drill string with reduced fouling, balling or packing off.
Type: Application
Filed: Dec 5, 2013
Publication Date: Jun 11, 2015
Inventors: Michael M Tomczak (Tomball, TX), James Shamburger (Spring, TX)
Application Number: 14/098,489