Patent Application
20100089662
The present invention relates in general to drill bits and, more specifically, to protecting the drill bit and casing from damage during tripping in and drill out operations.
A variety of drill bits, including fixed and rotary bits, are used in drilling operations. One part of the drilling operation that occurs before penetration into a formation involves drilling through a concrete pad at the bottom of a borehole called the “shoe”. This operation is called “drill out”, wherein the cement is “tagged up” as the drill bit drills through the structure. Often this pad is formed from the residue of casing operations of the borehole but it may also form from intentional filling the bottom of the borehole with cement. The shoe functions to cap the formation at the bottom of the metal casing until the drilling operator wishes to drill into the formation below the shoe.
One significant problem that may occur during drill out is that the drill bit, upon initial contact with the shoe, may begin to move off-center from the center of the borehole. The drill bit may become temporarily destabilized and begin angling where it cuts a wider diameter hole than the planned hole diameter, called the “gauge diameter”. The drill bit may also begin “whirling”—a complex set of repeating rotational motions that also cause the bit to go off-center. Under such conditions, an unprotected drill bit may continue to spin outside its designed gauge diameter and eventually come into contact with the casing, severely damaging the cutting elements of the drill bit.
A drill bit spinning at normal operational speed may contact the borehole wall with tremendous force. This contact may cause several events to occur. For example, the drill bit may remain unstable and possibly build up more instability, causing it to wander off the intended drill path or drill at awkward angles. The drill bit, because of the rotational force it operates under, may ricochet off the side of the borehole and bounce towards the opposing sidewall. The cutters, especially the gauge cutters, may become directly exposed to the casing wall and impact the casing, leading to chipped, cracked, or complete destruction of the face of the cutting element, which may fail under a sudden shock impact. The casing wall itself may become scarred or gouged by the impact of the cutters, which are typically made of a very hard material that can cut through metal (such as polycrystalline diamond compact).
Accordingly, it is desirable to provide an apparatus that avoids the aforementioned limitations and allows for protection of the drilling components and casing interior during tripping in the hole and during the drill out process.
Apparatus and methods are disclosed to protect for the cutting elements, specifically the gauge cutters, from coming into contact with the borehole casing during both traversal down the hole and during drill out operations. For example, dynamic forces, including “whirl”, may cause the drill bit to either rotate off-center in the borehole or rotate in a diameter beyond the gauge diameter of the bit. The protective inserts of the present invention may prevent the cutting elements of the bit from coming into contact with the borehole casing by acting as a first point of impact for the bit, to minimize damage to the gauge cutters. The protective inserts may also minimize gouging of the casing wall by acting as a smooth bearing surface during bit rotation. The protective inserts of the present invention may act as an additional gauge after abrasion wears the invention down to gauge diameter.
A drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, is disclosed. The drill bit includes a blade comprising a gauge cutter operable to cut an earth formation at the gauge diameter, and a protective insert coupled the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance, wherein the protective insert is operable to engage the casing inner wall to substantially prevent the gauge cutter from engaging the casing inner wall as the drill bit is positioned through a selected length of the casing.
A method of protecting a gauge cutter of a drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, is disclosed. The method includes the steps of coupling a protective insert to the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance, positioning the drill bit within the casing, and preventing the gauge cutter from contacting the casing inner wall along a selected length of the casing.
The foregoing summary as well as the following detailed description of illustrative embodiments of the invention will be better understood when read in conjunction with the appended drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown herein. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The invention may take physical form in certain parts and arrangement of parts. For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.
As used herein, the terms “up” and “down”; “upper” and “lower”; “uphole” and “downhole” and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point.
An apparatus and method to protect the cutting elements of a drill bit, specifically the gauge cutters, from coming into contact with the borehole casing during both traversal down the hole and during drill out operations are disclosed. The drill bit comprises one or more protective inserts that protrude beyond the gauge distance and into the drift distance between the drill bit and inner wall of the casing. These exposed protective inserts prohibit the gauge cutters from engaging the casing wall. The protective inserts may also allow the drill bit to rotate within the casing without damaging the casing. Once the drill bit drills into the formation, the protective inserts may ablate to allow the gauge cutters to engage the formation. Accordingly, the present invention provides active gauge protection for the drill bit by providing a physical barrier between the cutters and the casing.
Bit 10 includes one or more bit blades 20. Bit blades 20, may be positioned and spaced uniformly between one another, extend from an area beginning approximately about the centerline 16 and radiate outward towards the outer diameter of bit 10. As blades 20 reach the outer diameter of bit 10, the angle of blade 20 may become substantially parallel with centerline 16, e.g., an area on blade 20 substantially parallel to casing 50 and substantially perpendicular to the bottom of the borehole.
One or more super-abrasive cutters 22, made of materials such as polycrystalline diamond compact, matrix, diamond impregnation, or tungsten carbide, for example, are coupled to each blade 20. The cutting face 23 of each cutter 22 may face in the general direction of the operational rotation of bit 10. Each cutter 22, as bit 10 rotates during normal operation, may create cuttings by interacting in an abrasive manner with the concrete shoe 90 (shown in
Referring to
To accomplish the drillout operation and initial penetration of the formation beneath shoe 90, bit 10 may be designed to have an operational diameter called a gauge diameter 62. Gauge diameter 62 may be diameter of the hole drilled by bit 10 and may represent the circular area effectively contacted by cutters 22. The space left between gauge diameter 62 and casing diameter 52 may be referred to as drift distance 72. Drift distance 72 on all sides of bit 10 may permit bit 10 to operate within casing 50 unencumbered and may also permits fluid and debris to flow uphole and away from cutting faces 23. Drift distance 72 may also allow for potential variations in casing diameter 52 due to inconsistent drilling, formation movement, or casing buckling while still allowing a tool with a certain gauge diameter 52 can pass through to the bottom of casing 50.
As shown in
Referring again to
Protective insert 100 may be composed of a variety of materials suitable for drilling operations, or the downhole environment. For example, protective inserts 100 may comprise TCI (tungsten carbide) inserts, PDC (polycrystalline diamond compact) inserts, matrix material inserts, diamond impregnated inserts, or any other suitable material. The size and material of protective insert 100 may be selected to provide protection for gauge cutters 25 from the force of impact, and may be selected such that protective insert 100 wears down at a selected rate. For example, protective inserts 100 may be selected to wear down at a higher rate than the superabrasive cutting faces 23 of gauge cutters 25, especially when in direct contact with a virgin rock formation. For instance, during drilling operations after drillout, protective inserts 100 may quickly wear down to gauge diameter 62 and allow the gauge cutters 25 to engage the formation.
Protective insert 100 may be coupled to bit 10 by any method suitable for drilling operations or the downhole environment. For example, protective insert 100 may be brazed or infiltrated into bit 10 e.g., a matrix bit. Bit 10 may comprise apertures sized or threaded to receive protective inserts 100. Protective inserts 100 may be affixed to bit 10 by pressing, pinning or threading protective inserts 100 into these apertures, for example. Protective insert 100 may also be brazed into such apertures. Protective inserts 100 may be removably coupled to bit 10 to allow ease of repair or replacement.
Protective insert 100 may be shaped and sized to selectively contact or engage the inner surface of casing 50, e.g., to absorb impact and quickly ablate. For example, protective insert 100 may comprise a dome or curved formation, such as a half-dome or sphere. Protective insert 100 may be shaped to distribute the force of impact throughout the protective insert 100 rather than the point of contact. Protective insert 100 may act as a bearing surface against casing 50 so as to minimize friction against the wall, thereby preventing gouging. Protective insert 100 may be shaped or selected, e.g., by the selected material or a smooth gradient shape, to minimize rotation disruption of bit 10 after impact. For example, protective insert 100 may comprise shapes with a smooth contact point, such as an elliptical, oval, ovoid, “pill”, or “bullet” shape, for example.
The illustrated embodiments of the active gauge protection may provide a number of advantages. For example, protective inserts 100 protect gauge cutters 25 during the entry, lowering, and drillout of concrete shoe 90 at the bottom of the hole by providing a physical barrier between the gauge cutters and metal casing 50. Protective inserts 100 may act as the first physical contact points between drill bit 10 and metal casing 50 should drill bit 10 wander off-center, through drift distance 72, and into the casing, e.g., bit whirl. Protective inserts 100 may act as the point of contact to absorb the force and prevent movement that would expose the hardened cutters to the casing wall, which may damage or gouge the interior of casing 50.
The illustrated embodiments of protective inserts 100 may also provide the first point of contact if drill bit 10 moves or deviates toward the casing wall. Protective inserts 100 may act as a smooth bearing surface to allow drill bit 10 to continue to rotate while in contact with the casing wall either during drillout of the shoe or traversal down the hole. Protective inserts 100 may comprise curved and smooth surface as well as its material of construction help to both reduce the impact of the bit against the metal wall of the casing and prevent gouging by the harder, more durable cutting elements. Materials of construction can vary to ensure compatibility with the casing wall as well as act as a force-absorbing material. Protective inserts 100 may serve as a guide to assist with centering drill bit 10 as it is positioned into and through casing 50.
The illustrated embodiments of protective inserts 100 may also act as an additional gauge guide once the drill bit penetrates concrete shoe 90 at the bottom of casing 50 and engages the rock formation. During drillout, protective inserts 100 may continue to provide both bit and casing lateral protection and resist abrasion from the shoe material; however, upon entering virgin formation beneath the shoe, the material of construction may quickly wears down to gauge diameter against the rock formation, thereby fully exposing the gauge cutters to the formation. The material and shape for protective inserts 100 can be selected to optimize this effect based on the properties of the target rock formation.
In another example, once the operators set casing 50, a smaller drill bit 10 may be used to drill the next interval. As a result, there is some play between the casing 50 and the next hole size to be drilled. This difference may allow drill bit 10 to bounce around in the casing, which may damage drill bit 10 and the casing. Protective inserts 100 may act to protect both drill bit 10 and casing 50 in this situation. Conventional drill bits do not address this problem because conventional designs, e.g., such as the standards set forth by the American Petroleum Institute (API), typically do not permit components of the drill bit to extend beyond the drill diameter.
From the foregoing detailed description of specific embodiments of the invention, it should be apparent that an apparatus and method for protecting the drill bit and casing that are novel have been disclosed. Although specific embodiments of the invention have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed embodiments without departing from the spirit and scope of the invention as defined by the appended claims which follow.
