Patent Application
20080251293
The present invention relates generally to drilling tools and more particularly to drill bits.
Cutters are often utilized in drill bits for shearing through rock formations. Oftentimes, these cutters become dull and require replacement, which limits the rate of penetration into the rock as well as footage drilled. The cutters may be damaged by impact, thermal degradation and abrasive wear, factors which significantly reduces the life of the cutting elements. For example, while polycrystalline diamond compact (PDC) bits are effective when drilling in soft formations, the PDC bits' performance has been limited while drilling in hard-rock and abrasive formations due to impact damage and wear.
The current trend in the industry is to force, vector, dynamic and energy balance PDC drill bits for stability purposes. However, these methods do not take into consideration the instability of the drill string. The drill string can have a dramatic effect on bit performance with respect to impact damage to cutters.
Therefore, there is a need to provide an apparatus and method for drilling using a drill bit operable to compensate for abnormal loading resulting from vibration and whirl associated with bit and/or drill string instability. There is also a need to provide drilling at an improved rate of penetration. There is a further need to prolong the cutter's life and the drill bit's life by reducing the rate of damage caused by thermal degradation and abrasive wear.
In view of the foregoing and other considerations, the present invention relates to methods and apparatus for improving drill bit performance and operational life by reducing the rate of damage caused by impact, thermal degradation and abrasive wear.
Accordingly, a cutter assembly for a drill bit is provided. The cutting assembly comprises a planar table, and a cutter substrate coupled to the planar table, wherein the cutter substrate has a cutter body axis and wherein the planar table is operable to rotate about the cutter body axis. In another embodiment, the cutter assembly comprises a planar table, and a dampening mechanism operable to reduce an impact force applied to the drill bit in response to contact between the planar table and a solid surface as the drill bit engages the solid surface.
A method for drilling a formation is provided. The method includes the steps of providing a drill bit comprising a cutter assembly, wherein the cutter assembly comprises a cutter substrate having a planar table operable to rotate axially about a cutter body axis and comprising a cutting surface, disposing the drill bit in a well bore adjacent to a formation, rotating the drill bit around a bit axis, engaging a portion of the planar table to the formation to cut a portion of the formation, and rotating the planar table.
In another embodiment, the method includes the steps of providing a drill bit comprising a cutter assembly, wherein the cutter assembly comprises a planar table and a dampening mechanism, disposing the drill bit in a well bore adjacent to a formation, rotating the drill bit around a bit axis, engaging a portion of the planar table to the formation to cut a portion of the formation, and dampening at least a portion of the impact on the drill bit as the drill bit engages the formation.
The foregoing has outlined the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.
The foregoing and other features and aspects of the present invention will be best understood with reference to the following description of a specific embodiment of the invention, when read in conjunction with the accompanying drawings, wherein:
The following discussion is presented to enable a person skilled in the art to make and use the invention. The general principles described herein may be applied to embodiments and applications other than those detailed below without departing from the spirit and scope of the present invention as defined by the appended claims. The present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods, and devices for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
Although
In this embodiment, the cutter base 110, which may also be rotatable relative to the cutter substrate 120, is substantially cylindrical in shape and comprises a first bearing base 112 and a first bearing surface 114, which is coupled to the first bearing base 112. The first bearing base 112 is preferably made of carbide and may include other materials, such as cobalt metal, for the cementing constituent. Although this embodiment uses carbide in the first bearing base 112, other materials, known to those skilled in the art, may be used without departing from the scope and spirit of the present invention. The first bearing surface 114 is preferably made of diamond and preferably comprises a polycrystalline diamond table. Although this embodiment uses diamond for the first bearing surface 114, other materials, including impregnated diamond or pressed inserts that mimic the properties of impregnated diamonds, may be used without departing from the scope and spirit of the present invention. The first bearing surface 114 is coupled to the first bearing base 112 by methods known to those skilled in the art. Also, although this embodiment uses a cutter base 110 which is substantially cylindrical in shape, other geometrical shapes may be used without departing from the scope and spirit of the present invention.
In this embodiment, the cutter substrate 120 is substantially cylindrical in shape and comprises a second bearing surface 122, a second bearing base 124 which is coupled to the second bearing surface 122, and a planar table 126 which is coupled to the opposite side of the second bearing base 124. The second bearing surface 122 is preferably made of diamond and preferably comprises a polycrystalline diamond table. The second bearing surface 122 rotatably couples with the first bearing surface 114, thereby forming a rotary bearing 128 during operation. Although this embodiment uses diamond for the second bearing surface 122 and the planar table 126, other materials, including impregnated diamond or pressed inserts that mimic the properties of impregnated diamonds, may be used without departing from the scope and spirit of the present invention. The second bearing base 124 is preferably made of carbide and may include other materials, such as cobalt metal, for the cementing constituent. Although this embodiment uses carbide in the second bearing base 124, other materials, known to those skilled in the art, may be used without departing from the scope and spirit of the present invention. The second bearing surface 122 and the planar table 126 are coupled to the second bearing base 124 by methods known to those skilled in the art. Also, although this embodiment uses a cutter substrate 120 which is substantially cylindrical in shape, other geometrical shapes may be used without departing from the scope and spirit of the present invention. Moreover, although this embodiment uses a rotary bearing 128 to facilitate the rotation of planar table 126, other mechanisms, including other bearing types, known to those skilled in the art, may be used without departing from the scope and spirit of the present invention.
In this embodiment, the second bearing base 124 comprises an inner portion 134 and an outer portion 136. The diameters of the inner portion 134 of the second bearing base 124 and the second bearing surface 122 are slightly larger than the diameters of the outer portion 136 of the second bearing base 124 and the planar table 126. A lip 130 is preferably provided at the location where these two diameters meet. The lip 130 couples with the sleeve 140 to allow the cutter substrate 120, and hence the planar table 126, to freely rotate axially around a cutter body axis 132, yet remain securely fit within the sleeve 140.
In this embodiment, the sleeve 140 is substantially cylindrical in shape and comprises a first portion 142 and a second portion 144. The internal diameter of the first portion 142 of the sleeve 140 is large enough to allow the inner portion 134 of the second bearing base 124, the second bearing surface 122 and the cutter base 110 to fit within it. When using the optional dampening mechanism 150, the dampening mechanism 150 would also fit within the internal diameter of the first portion 142 of the sleeve 140. The internal diameter of the second portion 144 of the sleeve 140 is preferably sized to allow the outer portion 136 of the second bearing base 124, located above the lip 130, to fit within it; but not the inner portion 134 of the second bearing base 124, located below the lip 130, or the cutter base 110. Although this embodiment utilizes the mechanical means of using the lip 130 to securely fit the cutter substrate 120 within the sleeve 140 while still allowing the cutter substrate 120, and hence the planar table 126, to rotate around the cutter body axis 132, other mechanisms may be used to accommodate this rotatable feature without departing form the scope and spirit of the present invention. The length of sleeve 140 is selected to allow at least a portion of the planar table 126 to remain exposed to the rock formation for cutting purposes. The sleeve 140 can be made of any material, including titanium, carbide, stainless steel, high carbon steel, alloys of these listed metals, or any other material suitable for use in drilling operations.
The dampening mechanism 150 may be positioned between the cutter base 110 and the drill bit 100 or profiled blade 104, and can be placed at this position, or screwed into this position, of the sleeve 140. In this embodiment, a belleville spring is used as the dampening mechanism 150. Although a belleville spring is used as the dampening mechanism 150, any other mechanical, magnetic, or electrical mechanism or engineered materials may be used as the dampening mechanism 150 without departing from the scope and spirit of the present invention. Dampening mechanism 150 may be pre-loaded or selected such that it dampens forces exerted on the planar table 126, exceeding a selected amount. For example, the dampening mechanism 150 may activate when the force on the bit 100 is over approximately 1000 pounds force. As a result, the drill bit 100 may continuously adjust to compensate for abnormal loading, vibration and whirl, associated with the drill bit 100 or the drill string (not shown) instability. Although a 1000 pound force is used for commencing the dampening effect, any desired force can be selected, depending upon the selected rock formation or other factors, without departing from the scope and spirit of the present invention. Accordingly, dampening mechanism 150 may increase the longevity of the cutter assembly 105 by reducing the wear caused by impact.
The cutter assembly 105 may be positioned into a cutter pocket 160 located within the drill bit 100. The cutter assembly 105 may be coupled to the drill bit 100 via a variety of methods, including body welding, infiltration, friction lock, adhesive, brazing, threads, pin(s) or plug(s), some of which are illustrated in
Referring primarily to
This replenishment of the cutting edge of planar table 126 may allow for a number of benefits. For example, all edges of the planar table 126 may wear nearly evenly before replacement is required, thereby prolonging its life. Moreover, as the cutter substrate 120 rotates, heat is dissipated so as to reduce localized thermal degradation to the cutter substrate 120 by reducing the time that a specific portion of the cutting edge is subjected to the formation, thereby also increasing its life. This rotation is caused by the forces acting from the formation, or may be caused electrically, via a motor, or magnetically. The mechanism and power supply for providing active rotation in this latter case may be contained within the drill bit 100 and/or the drill string. The cutter substrate 120 has a second bearing surface 122 which couples to the first bearing surface 114 of the cutter base 110. The location where these two bearing surfaces 114, 122 meet acts as a rotary bearing 128. The surface friction at this interface is minimized due to the surface and material of the bearing surfaces 114, 122, e.g., diamond tables.
Dampening mechanism 150 may provide additional wear resistance to the planar table 126, such wear caused by impact. This dampening effect may be continuous or selectively activated, depending on the dampening mechanism 150 utilized. For example, a dampening mechanism 150 may be selected such that when the load on the planar table 126 exceeds a selected amount, such as about 1000 pounds force or greater, the dampening mechanism 150 may activate so as to reduce damage. By reducing damage to the cutter substrate 120 and prolonging its life, the rate of penetration greatly increases.
There are several advantages associated with using the drill bit 100 comprising one or more cutter assemblies 105 of the present invention. One of the main advantages is that the life of the cutting surface of drill bit 100 is extended dramatically due to the reduction of damage caused by thermal degradation, abrasive wear and impact. As a result, drill bits 100, especially PDC bits, may be able to drill into harder, more abrasive formations with an improved penetration rate than previously possible. Furthermore, there is a possibility that the number of profiled blades 104 required to drill the formation may be reduced, thereby increasing the penetration rate. In addition, by minimizing the number of profiled blades 104, the number of total cutter assemblies 105 may also be reduced. Moreover, the overall drill bit 100 cost may be reduced due to fewer profiled blades 104 per drill bit 100.
The cutting assembly of the present invention may utilize cylindrical cutters and retainer that are cylindrical and in line with the current industry standard. Accordingly, the present invention may be used with a wide variety of existing drill bits and drilling tools. Furthermore, dampening mechanism 150 may allow the cutter substrate 120 to absorb some impact when exposed to an abnormal load. As a result, the design of drill bit 100 may be simplified or otherwise improved. For example, the need for leaching cutters (not shown) may be eliminated. Furthermore, the cutter assembly 105 may become more cost effective. Moreover, the drill bit 100 may be self balancing and may have an improved resistance to impact. In addition, the drill bit 100 may be configured in such a way so as to offer dampening in both directions, along the cutter body axis 132 or the cutter assembly 105. Accordingly, tensile stresses acting on the planar table 126, stresses which can cause the planar table 126 to delaminate from the second bearing base 124, may be significantly reduced. Although the main advantages and the benefits from those advantages have been mentioned above, one skilled in the relevant arts may recognize additional advantages and benefits that may be realized.
Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.
