Patent Grant
8225888
1. Field of the Invention
The present invention relates generally to drilling a subterranean borehole and, more specifically, drilling structures disposed on the end of a casing or liner.
2. State of the Art
The drilling of wells for oil and gas production conventionally employs longitudinally extending sections or so-called “strings” of drill pipe to which, at one end, is secured a drill bit of a larger diameter. After a selected portion of the borehole has been drilled, the borehole is usually lined or cased with a string or section of casing. Such a casing or liner usually exhibits a larger diameter than the drill pipe and a smaller diameter than the drill bit. Therefore, drilling and casing according to the conventional process typically requires sequentially drilling the borehole using drill string with a drill bit attached thereto, removing the drill string and drill bit from the borehole, and disposing casing into the borehole. Further, often after a section of the borehole is lined with casing, which is usually cemented into place, additional drilling beyond the end of the casing may be desired.
Unfortunately, sequential drilling and casing may be time consuming because, as may be appreciated, at the considerable depths reached during oil and gas production, the time required to implement complex retrieval procedures to recover the drill string may be considerable. Thus, such operations may be costly as well, since, for example, the beginning of profitable production can be greatly delayed. Moreover, control of the well may be difficult during the period of time that the drill pipe is being removed and the casing is being disposed into the borehole.
Some approaches have been developed to address the difficulties associated with conventional drilling and casing operations. Of initial interest is an apparatus which is known as a reamer shoe that has been used in conventional drilling operations. Reamer shoes have become available relatively recently and are devices that are able to drill through modest obstructions within a borehole that has been previously drilled. In addition, the reamer shoe may include an inner section manufactured from a material which is drillable by drill bits. Accordingly, when cemented into place, reamer shoes usually pose no difficulty to a subsequent drill bit. For instance, U.S. Pat. No. 6,062,326 to Strong et al. discloses a casing shoe or reamer shoe in which the central portion thereof may be configured to be drilled through. In addition, U.S. Pat. No. 6,062,326 to Strong et al. discloses a casing shoe that may include diamond cutters over the entire face thereof, if it is not desired to drill therethrough.
As a further extension of the reamer shoe concept, in order to address the problems with sequential drilling and casing, drilling with casing is gaining popularity as a method for initially drilling a borehole, wherein the casing is used as the drilling conduit and, after drilling, the casing remains downhole to act as the borehole casing. Drilling with casing employs a conventional drill bit attached to the casing string, so that the drill bit functions not only to drill the earth formation, but also to guide the casing into the wellbore. This may be advantageous as the casing is disposed into the borehole as it is formed by the drill bit, and therefore eliminates the necessity of retrieving the drill string and drill bit after reaching a target depth where cementing is desired.
While this procedure greatly increases the efficiency of the drilling procedure, a further problem is encountered when the casing is cemented upon reaching the desired depth. While one advantage of drilling with casing is that the drill bit does not have to be retrieved from the wellbore, further drilling may be required. For instance, cementing may be done for isolating certain subterranean strata from one another along a particular extent of the wellbore, but not at the desired depth. Thus, further drilling must pass through or around the drill bit attached to the end of the casing.
In the case of a casing shoe that is drillable, further drilling may be accomplished with a smaller diameter drill bit and casing section attached thereto that passes through the interior of the first casing to drill the further section of hole beyond the previously attained depth. Of course, cementing and further drilling may be repeated as necessary, with correspondingly smaller and smaller components, until the desired depth of the wellbore is achieved.
However, drilling through the previous drill bit in order to advance may be difficult as drill bits are required to remove rock from formations and accordingly often include very drilling resistant, robust structures typically manufactured from materials such as tungsten carbide, polycrystalline diamond, or steel. Attempting to drill through a drill bit affixed to the end of a casing may result in damage to the subsequent drill bit and bottom-hole assembly deployed or possibly the casing itself. It may be possible to drill through a drill bit or a casing with special tools known as mills, but these tools are unable to penetrate rock formations effectively and the mill would have to be retrieved or “tripped” from the hole and replaced with a drill bit. In this case, the time and expense saved by drilling with casing would have been lost. Therefore, other approaches have been developed to allow for intermittent cementing in combination with further drilling.
In one approach, a drilling assembly, including a drill bit and one or more hole enlargement tools such as, for example, an underreamer, is used which drills a borehole of sufficient diameter to accommodate the casing. The drilling assembly is disposed on the advancing end of the casing. The drill bit can be retractable, removable, or both, from the casing. For example, U.S. Pat. No. 5,271,472 to Leturno discloses a drill bit assembly comprising a retrievable central bit insertable in an outer reamer bit and engageable therewith by releasable lock means which may be pressure fluid operated by the drilling fluid. Upon completion of drilling operations, the motor and central retrievable bit portion may be removed from the wellbore so that further wellbore operations, such as cementing of the drillstring or casing in place, may be carried out or further wellbore extending or drilling operations may be conducted. Since the central portion of the drill bit is removable, it may include relatively robust materials that are designed to withstand the rigors of a downhole environment, such as, for example, tungsten carbide, diamond, or both. However, such a configuration may not be desirable since, prior to performing the cementing operation, the drill bit has to be removed from the wellbore and thus the time and expense to remove the drill bit is not eliminated.
Another approach for drilling with casing involves a casing drilling shoe or bit adapted for attachment to a casing string, wherein the drill bit comprises an outer drilling section constructed of a relatively hard material and an inner section constructed of a drillable material. For instance, U.S. Pat. No. 6,443,247 to Wardley discloses a casing drilling shoe comprising an outer drilling section constructed of relatively hard material and an inner section constructed of a drillable material such as aluminum. In addition, the outer drilling section may be displaceable, so as to allow the shoe to be drilled through using a standard drill bit.
Also, U.S. Patent Application 2002/0189863 to Wardley discloses a drill bit for drilling casing into a borehole, wherein the proportions of materials are selected such that the drill bit provides suitable cutting and boring of the wellbore while being able to be drilled through by a subsequent drill bit. Also disclosed is a hard-wearing material coating applied to the casing shoe, as well as methods for applying the same.
However, as a further consideration, the prior art cutting elements may be difficult to drill through when disposed in a region of a casing shoe that is configured to be drilled through. Accordingly, there exists a need for improved cutting elements for use with casing shoes or bits that are configured to drill a borehole.
Moreover, casing bits that are configured to drill a casing section into a subterranean borehole have not, prior to the present invention, included features that may be advantageous. For instance, wear knots, as described with respect to U.S. Pat. No. 6,460,631, assigned to the assignee of the present invention and the disclosure of which is incorporated in its entirety by reference herein, have been limited to use on rotary drill bits for drilling a drill string into a subterranean formation. Also, while reaming drill bits have been used in the past, the inventors are unaware of a casing bit for drilling a casing section into a borehole and having the capability to enlarge or ream an initially smaller borehole, prior to the present invention. Conventional expandable reamers may include blades pivotably or hingedly affixed to a tubular body and actuated by way of a piston disposed therein as disclosed by U.S. Pat. No. 5,402,856 to Warren. Further, U.S. Pat. No. 6,360,831 to Åkesson et al. discloses a conventional borehole opener comprising a body equipped with at least two hole-opening arms having cutting means that may be moved from a position of rest in the body to an active position by way of a face thereof that is directly subjected to the pressure of the drilling fluid flowing through the body. In addition, there exists a need for improved fluid delivery configurations for delivering drilling fluid to the face of a casing shoe.
In addition, conventional casing shoes have not employed stress-related engineered cutting element placement. For instance, U.S. Pat. Nos. 6,021,859, 5,950,747, 5,787,022, and 5,605,198 to Tibbitts et al., assigned to the assignee of the present invention and the disclosures of which are incorporated in their entirety by reference herein, each disclose selective placement of cutting elements engineered to accommodate differing loads such as are experienced at different locations on the bit crown.
Further, conventional casing shoes have not employed depth-of-cut limiting structures. Particularly, U.S. Pat. No. 6,298,930 to Sinor et al., assigned to the assignee of the present invention and the disclosure of which is incorporated in its entirety by reference herein, discloses exterior features disposed on a drill bit that preferably precede, taken in the direction of bit rotation, cutters with which they are associated, and provide sufficient bearing area so as to support the bit against the bottom of the borehole under weight-on-bit without exceeding the compressive strength of the rock formation.
Therefore, it would be desirable to provide a casing bit design for drilling a casing section into a subterranean formation that encompasses the attendant advantages of wear knots, fluid delivery technology, and reaming technology. It would also be desirable to provide a casing bit for drilling a casing section into a subterranean formation effectively, but which is also capable of being drilled by conventional oilfield drill bits.
The present invention contemplates a casing bit configured for drilling a casing section into a subterranean formation. The casing bit of the present invention may include a connection structure for connecting the casing bit to a casing section, an inner profile, an outer profile, and a nose portion. Further, the casing bit may include a plurality of generally radially extending blades disposed on the nose portion, wherein at least one of the plurality of blades carries one or more cutting elements and at least one aperture formed in the nose portion of the casing bit and is configured for delivering drilling fluid from an interior of the casing bit to an exterior thereof. Also, the casing bit may include at least one gage section, the at least one gage section extending longitudinally from the adjacent nose portion of the casing bit.
The casing bit of the present invention may comprise at least one metal, metal alloy, or both, such as, for instance, steel, aluminum, brass, bronze, and may comprise tungsten carbide composites, such as tungsten carbide infiltrated with a hardenable binder, such as a copper-based binder. Further, a casing bit of the present invention may comprise an outer shell exhibiting a reasonably high compressive strength as well as at least one inner core that is relatively ductile material and more readily drillable than the outer shell. For instance, a casing bit of the present invention may comprise a steel outer shell and a phenolic inner core. Alternatively or additionally, the casing bit of the present invention may comprise an impregnated material that includes one or more of natural diamond, synthetic diamond, and carbide. The present invention also contemplates that the casing bit of the present invention may include a coating applied to the exterior thereof and is configured to inhibit adhesion between formation cuttings and the surfaces of the casing bit, inhibit wear, abrasion, or erosion to the surfaces of the casing bit, or both.
The casing bit of the present invention may include a plurality of blades that extend generally radially outwardly in a generally spiral fashion from the centerline to the radial outer extent of the casing bit. Also, the gage regions of each blade may extend longitudinally from the nose portion of the casing bit in a generally helical fashion. Alternatively, the casing bit of the present invention may comprise a bit body that does not include blades, but rather has a substantially symmetrical profile, with respect to the longitudinal axis thereof, that forms the outer surface of the casing bit and cutting elements may be affixed thereto. More particularly, polycrystalline diamond cutting elements, polycrystalline diamond stud-type cutting elements, percussion cutting elements, tungsten carbide cutting elements, or other cutting elements as known in the art may be installed upon such a casing bit.
In another aspect of the casing bit of the present invention, at least one rotationally trailing groove may be formed in at least one of the plurality of blades. For example, the at least one rotationally trailing groove may exhibit a tapered geometry in which the width of the at least one rotationally trailing groove increases along a direction of rotation of the casing bit, or, alternatively, the at least one rotationally trailing groove may exhibit a constant width along a direction of rotation of the casing bit.
As a further facet of the casing bit of the present invention, at least one aperture formed in the casing bit of the present invention may include a retention structure for disposing at least one of a nozzle and a sleeve. Of course, the at least one of a nozzle and a sleeve may be affixed within the retention structure via at least one of welding, brazing, and threaded surfaces and may be replaceable.
Also, the casing bit of the present invention may include an integral stem section which further comprises a float valve mechanism, a cementing stage tool, a float collar mechanism, a landing collar structure, other cementing equipment, or combinations thereof, as known in the art.
In another embodiment of the casing bit of the present invention, at least one rolling cone may be affixed to the nose portion thereof.
At least a portion of the casing bit may be configured to be drilled therethrough by way of a drilling tool having a drilling profile. Moreover, at least a portion of at least one of the inner profile and the outer profile of the casing bit may substantially correspond to the drilling profile of the drilling tool. Such a configuration may facilitate drilling into the casing bit, into the formation from the casing bit, or both.
In addition, cutting elements associated with a portion of the casing bit that is configured to be drilled through may differ from cutting elements associated with a region peripheral thereto. For instance, a majority of the cutting elements associated with a portion of the casing bit that is configured to be drilled through may differ from a majority of the cutting elements associated with a region peripheral thereto. In one example, the size of a majority of the cutting elements of a first portion of the plurality of cutting elements disposed in a casing bit region to be drilled through may be smaller than the size of a majority of the cutting elements of a second portion of the plurality of cutting elements disposed in a peripheral region. Alternatively, the average amount of abrasive material contained by each of the cutting elements of a region that is configured to be drilled through may be less than the average amount of abrasive material contained by each of the cutting elements of a peripheral region. As another alternative, each of, or a majority of, the cutting elements of a region of the casing bit that is configured to be drilled through may be substantially carbide-free. In addition, at least one of the cutting elements generally within a region of the casing bit that is configured to be drilled through may comprise a first grade of cutting element based upon at least one inherent quality related to wear characteristics, while at least one of the cutting elements in a peripheral region may comprise a second grade of cutting element based upon at least one inherent quality related to wear characteristics, wherein the inherent quality of the second grade of cutting element is generally different than the inherent quality of the first grade of cutting element.
The present invention also contemplates that a first plurality of cutting elements disposed upon a casing bit may be more exposed than the second plurality of cutting elements disposed thereon. Further, the first plurality of cutting elements may be configured to initially engage and drill through materials and regions that are different from subsequent materials and regions that the second plurality of cutting elements is configured to engage and drill through. Particularly, the first plurality of cutting elements may comprise tungsten carbide cutting elements and the second plurality of cutting elements may comprise polycrystalline diamond cutting elements.
In addition, cutting elements may be placed upon a casing bit of the present invention according to above-mentioned and incorporated U.S. Pat. Nos. 6,021,859, 5,950,747, 5,787,022, and 5,605,198 to Tibbitts et al.
The present invention also contemplates cutting elements for use upon a casing bit of the present invention. Particularly, a cutting element of the present invention may comprise a superabrasive layer bonded to a substrate wherein the substrate may be substantially free of carbide. For instance, a cutting element substrate may comprise steel, tungsten, titanium-zirconium-molybdenum (TZM), molybdenum, bronze, brass, aluminum, or ceramic. In addition, a substantially carbide-free cutting element of the present invention may be formed in response to drilling a subterranean formation, wherein the drilling removes at least a portion of the carbide within the substrate. Also, the superabrasive table of a cutting element may also be sized and configured to wear away in relation to drilling a subterranean formation, so that a relatively small amount of superabrasive material remains, and may exist upon a casing bit employing same at the time that a drilling tool is employed to drill therethrough. In addition, the present invention contemplates that a cutting element material exhibiting relatively high resistance to one or more of abrasion, erosion, and wear may be removed by one or more of mechanical, thermal, or chemical degradation.
In yet another embodiment of a cutting element of the present invention, the superabrasive material included therein may be sized and positioned to facilitate drilling through a casing bit employing same with a drilling tool. More particularly, the abrasive volume of the cutting element may be sized and configured so as to reduce the damage that may be caused in drilling through a casing bit employing one or more of the cutting elements.
The present invention also contemplates a casing bit that is configured as a reamer. More particularly, the casing bit reamer of the present invention may include a pilot drill bit at the lower longitudinal end thereof and an upper reaming structure that is centered with respect to the pilot drill bit and includes a plurality of blades spaced about a substantial portion of the circumference, or periphery, of the reamer. Alternatively, the casing bit reamer of the present invention may be configured as a bicenter bit assembly, which employs two longitudinally superimposed bit sections with laterally offset axes in which usually a first, lower and smaller diameter pilot bit section is employed to commence the drilling, and rotation of the pilot bit section may cause the rotational axis of the bit assembly to transition from a pass-through diameter to a reaming diameter.
Additionally, a casing bit of the present invention may be configured with at least one of an explosive agent and an incendiary agent. As may be appreciated, use of an explosive agent, an incendiary agent, or both, in proximity to a casing bit may facilitate a drilling tool drilling therethrough or passing therethrough. Particularly, a destructive element may be configured to substantially remove, destroy, perforate, degrade, weaken, or otherwise render more drillable a casing bit proximate thereto.
In another aspect of the present invention, a substance delivery assembly may be provided, sized, and configured for selectively delivering a substance to interact with a casing bit to abrade, erode, perforate, dissolve, degrade, weaken, or otherwise render more drillable, a casing bit proximate thereto. For instance, acid or a particulate abrasive may be selectively delivered proximate a casing bit.
In a further facet of the present invention, a casing bit of the present invention may be configured to be preferentially frangible, preferentially weakened, or preferentially fractured. Particularly, grooves or recesses disposed upon the interior, exterior, or both the interior and exterior of the casing bit may be sized and configured to provide selective failure characteristics. For instance, a casing bit may be preferentially weakened to allow failure into sections, or which may allow preferential deformation. Such a configuration may facilitate drilling through the casing bit by removing relatively small pieces thereof by way of drilling fluid, or by deforming the casing bit advantageously for drilling therethrough.
The present invention also contemplates that a casing bit of the present invention may be fabricated from a fiber-reinforced composite, wherein the fiber-reinforced composite comprises one or more fibers disposed within a matrix material. Further, the one or more fibers may extend in a generally circumferential fashion. More specifically, the one or more fibers may be oriented in a concentric fashion or, alternatively, in a spiral fashion.
Also, a casing bit of the present invention, as mentioned above, may comprise one or more shells of differing materials, without limitation. Thus, at least one of the shells of a casing bit of the present invention may comprise a fiber-reinforced composite.
The present invention further contemplates that cutting elements associated with a portion of the casing bit that is configured to be drilled through may be affixed differently from cutting elements associated with a region peripheral thereto. Explaining further, cutting elements associated with a portion of the casing bit that is configured to be drilled through may be configured to be released from the casing bit. For instance, at least one cutting element associated with a portion of the casing bit that is configured to be drilled through may be affixed thereto by way of adhesive. The adhesive may exhibit sufficient strength for drilling operations, but may, in the presence of one or more of heating, impact loading, or increased forces not present during drilling, fail and release cutting elements affixed therewith. Also, a solder may be used to affix at least one cutting element to a casing bit. Alternatively, an electrically disbonding material may affix at least one cutting element to a casing bit that is configured to be drilled through. Accordingly, the electrically disbonding material may fail or weaken in response to electric current flowing therethrough, which may allow the at least one cutting element to be released or removed from the casing bit. In another example, a fastening element may affix at least one cutting element to a casing bit, wherein the at least one cutting element is associated with a portion of the casing bit that is configured to be drilled through. Particularly, an end region of the cutting element may be positioned to allow drilling thereinto, prior to drilling into the abrasive material of the cutting element, by a drilling tool drilling into the inner profile of the casing bit. Alternatively, the cutting element may comprise a stud body that has an end region that extends so as to allow a drilling tool to drill thereinto prior to drilling the abrasive material of the cutting element. The end region of a fastening element or of a stud body of a cutting element may be threaded, welded, pinned, brazed, deformed, or otherwise affixed to the casing bit.
In yet another aspect of the present invention, at least two casing bits of different diameter and having associated casing sections may be assembled to form a drilling assembly for drilling into subterranean formations, wherein radially adjacent casing sections are selectively releasably affixed to one another and wherein the at least two casing bits and casing section are arranged in a telescoping relationship. The smaller casing bit(s) of the at least two casing bits may be configured to drill through the next larger casing bit.
Also, at least two casing sections of different diameter disposed in a telescoping relationship may comprise an assembly for drilling into a subterranean formation. Particularly, a drilling tool which is sized and configured to drill a diameter exceeding the largest diameter of the casing sections may be disposed at the longitudinally preceding end of the at least two casing sections, in relation to the direction of drilling, and radially adjacent casing sections may be selectively releasably affixed to one another.
In another aspect of the present invention, at least a portion of the leading face of a blade of a casing bit may comprise a superabrasive material. For instance, at least a portion of the leading face of a blade of a casing bit may comprise polycrystalline diamond compact (PDC) or thermally stable polycrystalline diamond (TSP) material.
In yet another embodiment of the present invention, at least one reaming blade of a casing bit reamer may be movable or expandable. The at least one expandable blade may be held in place by one or more frangible elements that are failed by a force developed by drilling fluid flowing through an orifice.
In a further aspect of the casing bit of the present invention, at least one sensor configured for measuring a condition of drilling, a condition of the casing bit, or a formation characteristic may be included by the present invention.
The present invention also contemplates that the casing bit of the present invention may include discrete cutting element retention structures for carrying cutting elements. Therefore, the casing bit of the present invention may not include blades or blade-like structures at all. Further, the casing bit of the present invention may be configured for percussion drilling. Thus, accordingly, a casing bit of the present invention may include a plurality of percussion inserts configured for percussion drilling.
Other features and advantages of the present invention will become apparent to those of ordinary skill in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims.
In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention:
During drilling, fluid courses 24 between circumferentially adjacent blades 22 may be provided with drilling fluid flowing through apertures 33 that extend between the interior of the casing bit 12 and the face 26 thereof. Formation cuttings are swept away from the cutting elements (not shown) by drilling fluid emanating from apertures 33, the fluid moving generally radially outwardly through fluid courses 24 and then upwardly through junk slots 35 to an annulus between the casing section 40 (
Once the casing bit 12 and the casing section 40 are affixed to one another, the casing bit assembly 11 may be rotated so as to cause casing bit 12 to drill through subterranean formation 42, forming borehole 32, as shown in
Accordingly, as shown in
However, in some instances, the size and placement of apertures 33 that are employed for drilling operations may not be particularly desired for cementing operations. For instance, the apertures configured to deliver a drilling fluid to the cutting elements of the casing bit 12 may become plugged or obstructed prior to or during delivery of cement therethrough. As shown in
Alternatively, the one or more frangible regions 19 and apertures 33 may be configured so that cement is selectively delivered through the one or more frangible regions 19. For instance, an obstruction element may be “dropped” into the casing section 40, which is configured to engage and seal one or more of the apertures 33 of the casing bit 12. As another alternative, the apertures 33 may be sized so that a hydraulic pressure may build within the casing bit 12 that is sufficient to rupture or otherwise open at least one of the one or more frangible regions 19. The hydraulic pressure may be generated by flow of drilling fluid, cement, or another fluid. It may be further noted that the viscosity of the fluid may be tailored in order to generate pressure within the casing bit 12 for rupturing or opening at least one of the one or more frangible regions 19.
As may further be seen in reference to
More particularly, as shown in
In one embodiment, component 47 may comprise a float collar, as shown in
Referring to
Generally, referring to
Casing bit 12 may include an outer profile 18 defined along its lowermost region, the lowermost region configured to drill through a subterranean formation. The outer profile 18 of casing bit 12 refers to either the drilling profile 14 of the casing bit 12, as explained above in relation to drilling tool 10, or the exterior geometry of the casing bit 12. According to the present invention, casing bit 12 may include an inner profile 16 which substantially corresponds to the drilling profile 14 of drilling tool 10. Such a configuration may provide greater stability in drilling through casing bit 12. Particularly, forming the geometry of drilling profile 14 of drilling tool 10 to conform or correspond to the geometry of the inner profile 16 of casing bit 12 may allow for cutters (labeled “50” in
For instance, referring to
Similarly,
Alternatively, as shown in
Of course, the inner profile 16 of casing bit 12 may also be shaped in relation to the outer profile 18 thereof. Selectively configuring the inner profile 16 of casing bit 12 in relation to the outer profile 18 thereof may be advantageous to stabilize the drilling tool 10 as it drills through casing bit 12. More specifically, the distance or thickness between the inner profile 16 and outer profile 18 of casing bit 12 may be configured to provide a suitable stabilizing bore surface formed by the formation below the outer profile 18 of the casing bit 12.
In another aspect of the present invention, as shown in
Accordingly, as may be seen by reference to
Turning now to
In another aspect of the present invention,
As discussed above, a casing bit of the present invention may have an outer profile that exhibits an inverted cone geometry. As shown in more detail in
Blades 122, as shown in
During drilling, fluid courses 124 between circumferentially adjacent blades 122 may be provided with drilling fluid flowing from apertures 133 that extend from the interior of the casing bit 112 to the face 126 thereof. Formation cuttings may be swept away from cutting elements 140 by drilling fluid emanating from apertures 133, the fluid moving generally radially outwardly through fluid courses 124 and then upwardly through junk slots 135 to an annulus between the casing section (not shown) to which the casing bit 112 may be affixed.
In addition, as shown in
Similarly, as shown in
More particularly,
Of course, the present invention contemplates that the size and configuration of rotationally trailing grooves may be selected and tailored for providing sufficient strength to the blades 168 for drilling. Thus, constant width rotationally trailing grooves 181 may be desirable in particular blade geometries while tapered rotationally trailing grooves 180 may be a desirable configuration in other blade geometries.
As mentioned above in relation to
As mentioned above, cutting elements may be used in combination with the casing bit of the present invention. However, conventional rotary drill bits are not configured for drilling through a drill bit or casing bit which carries PDC cutters within the area intended to be removed. Accordingly, the present invention contemplates cutting elements that may be configured to facilitate drilling through the casing bit upon which they are disposed.
In a first embodiment, a cutting element of the present invention may comprise a superabrasive layer bonded to a substrate wherein the substrate may be substantially free of carbide. The term “carbide,” as used herein, refers to a compound of carbon and one or more metallic elements. Carbide may generally exhibit relatively hard and abrasive properties. Particularly, tungsten carbide is known to exhibit a relatively high hardness as well as a relatively high resistance to abrasion, erosion, or both. Accordingly, the use of conventional cutting elements that include cemented tungsten carbide within a casing bit of the present invention may cause difficulty in drilling therethrough.
Thus,
Thus, as explained above, “substantially free” of carbide may mean completely free from carbide. However, the present invention also contemplates that a substrate that is “substantially free” of carbide may include other configurations wherein carbide forms a minor portion of the entire substrate 204 as well. Moreover, a substantially carbide-free cutting element of the present invention may be formed in response to drilling a subterranean formation, wherein the drilling removes at least a portion of the carbide within the substrate.
For instance, as shown in
Also, in another embodiment of a cutting element 210 of the present invention, as shown in
Of course, the superabrasive table of a cutting element may also be sized and configured to wear away in relation to drilling a subterranean formation, so that a relatively small amount of superabrasive material may exist upon a casing bit employing same at the time that a drilling tool is employed to drill therethrough. Thus, an amount of superabrasive material comprising a superabrasive table of a cutting element of the present invention may be selectively tailored to form a substantially superabrasive-free cutting element in response to drilling a subterranean formation. In other words, at least a portion of the superabrasive table of a superabrasive cutting element of the present invention may be configured to substantially wear away or be removed in response to drilling a subterranean formation. Such a configuration may reduce the amount of superabrasive material affixed to the casing bit that is encountered by a drilling tool employed to drill therethrough.
In addition, the present invention is not limited to wearing the amount of abrasive material within a cutting element or substrate by way of the subterranean formation alone. Rather, abrasive material comprising a cutting element superabrasive table or substrate including diamond, carbide, ceramic, or other material exhibiting relatively high resistance to one or more of abrasion, erosion, and wear may be removed by one or more of mechanical, thermal, or chemical degradation. For instance, upon drilling to a desired depth, the casing bit of the present invention may be operated with drilling fluid that contains a chemical with an affinity for carbon. For example, iron-containing, cobalt-containing, or other metal containing compounds such as metallic salts may have an affinity for carbon at relatively high temperatures. Thus, the casing bit may be drilled without drilling fluid or very little drilling fluid, so as to heat the abrasive materials sufficiently to cause one or more of chemical, mechanical, and thermal degradation, thus rendering an initially abrasive material substantially nonabrasive. Accordingly, a material that initially exhibits relatively high resistance to one or more of abrasion, erosion, and wear may be rendered to exhibit substantially little resistance to any of abrasion, erosion, and wear, or may be removed from the casing bit.
In yet another embodiment of a cutting element of the present invention, the superabrasive material included therein may be sized and positioned to facilitate drilling through a casing bit employing same with a drilling tool. More particularly, the abrasive volume of the cutting element may be sized and configured so as to reduce the damage that may be caused in drilling through a casing bit employing one or more of the cutting elements. “Abrasive volume,” as used herein, is intended to indicate a material that exhibits at least one of relatively high hardness, abrasive-resistance, and erosion-resistance. For instance, an abrasive volume may include carbide, diamond, boron nitride, ceramic, or other material exhibiting at least one of relatively high hardness, abrasive-resistance, and erosion-resistance. For example, a cutting element which is generally configured as a portion of a cylinder, according to U.S. Pat. No. 5,533,582 to Tibbitts, assigned to the assignee of the present invention and the disclosure of which is incorporated in its entirety by reference herein, may be employed by the casing bit of the present invention.
As shown in
Further, the casing bit of the present invention may employ selective cutting element configuration and placement. Particularly, cutting elements may be selectively positioned and configured in relation to the portion of the casing bit to be drilled through. Such a configuration may be advantageous in reducing the damage to a drilling tool used to drill through a casing bit of the present invention.
For instance,
For example, at least one of the cutting elements 332 generally within region x1 comprises a first grade of cutting element 332 based upon at least one inherent quality related to wear characteristics, and at least one of the cutting elements 332 generally within region x2 comprises a second grade of cutting element 332 based upon at least one inherent quality related to wear characteristics, wherein the inherent quality of the second grade of cutting element 332 is generally different than the inherent quality of the first grade of cutting element 332. In such an example, it may be advantageous to select the first grade of cutting element 332 in region x1 to exhibit wear characteristics that are inferior to the wear characteristics of the second grade of cutting element 332 in region x2. Alternatively, a majority of the cutting elements 332 in region x1 comprises a first grade of cutting element 332 based upon at least one inherent quality related to wear characteristics, and a majority of the cutting elements 332 generally within region x2 comprises a second grade of cutting element 332 based upon at least one inherent quality related to wear characteristics, wherein the inherent quality of the second grade of cutting element 332 is generally different from or inferior to the inherent quality of the majority of the first grade of cutting element 332.
Alternatively, or additionally, as discussed above, the amount of abrasive material comprising cutting elements 332 generally within region x1 may be adjusted to substantially wear away or be removed in response to drilling a subterranean formation to facilitate drilling through a casing bit employing same. Thus, the above-mentioned cutting elements 200, 201, 210, and 220 as described in relation to
Explaining further, since the inherent quality related to wear characteristics and the amount of abrasive volume within a cutting element may (assuming smooth wear of the cutting element) determine the amount of subterranean formation that may be cut or removed, a cutting element of the present invention may be tailored in this regard. Thus, an inherent quality related to wear characteristics, the amount or volume of abrasive material contained by each grade of cutting element, or both, may be tailored or selected in relation to a section of subterranean formation through which the casing bit 312 is to drill. Such a configuration may provide a method to facilitate removal of region x1 of casing bit 312 by way of drilling therethrough after the casing bit 312 has drilled a casing section (not shown) into a subterranean formation. Summarizing, the abrasive volume of a cutting element of the present invention may be configured to substantially wear away in response to an expected amount of drilling.
Accordingly, where the casing bit 312 of the present invention includes a plurality of cutting elements 332 wherein a first portion of the plurality of cutting elements 332 is disposed generally within region x1 and a second portion of the plurality of cutting elements 332 is disposed generally within region x2, the average amount of abrasive material contained by each of the cutting elements 332 of the first portion of the plurality of cutting elements 332 may be less than the average amount of abrasive material contained by each of the cutting elements 332 of the second portion of the plurality of cutting elements 332. In yet another alternative, the cutting elements 332 or a majority thereof in region x1 may be sized differently than the cutting elements 332 in region x2. Such a configuration may reduce the amount of materials exhibiting at least one of relatively high hardness, relatively high abrasive-resistance, and relatively high erosion-resistance within region x1 of casing bit 312. In addition, smaller cutters may be more easily flushed from the borehole by drilling fluid delivered from a drilling tool (not shown), which drills through casing bit 312.
In a further aspect of the present invention relating to cutting elements disposed on a casing bit of the present invention, cutting elements may be selectively placed upon a casing bit of the present invention according to the concepts and teachings of U.S. Pat. Nos. 6,021,859, 5,950,747, 5,787,022, and 5,605,198 to Tibbitts et al., the disclosure of each of which is mentioned and incorporated in its entirety hereinabove. Accordingly, cutting elements may be engineered and selectively placed upon a casing bit of the present invention to accommodate differing loading or stress conditions such as are experienced at different locations thereon.
In yet another aspect of the present invention, a casing bit of the present invention may be configured with a first plurality of cutting elements disposed thereon that are sized, configured, and positioned to drill through a casing bit or shoe or other drilling string component, while a second plurality of cutting elements disposed thereon are sized, configured, and positioned to drill into a subterranean formation.
More particularly,
Accordingly, the first plurality of cutting elements 386 may be configured differently than the second plurality of cutting elements 384. Particularly, the first plurality of cutting elements 386 may comprise tungsten carbide cutting elements, while the second plurality of cutting elements 384 may comprise polycrystalline diamond cutting elements. Such a configuration may facilitate drilling through a casing shoe or bit as well as the cement thereabout with primarily the first plurality of cutting elements 386. However, upon passing into a subterranean formation, the abrasiveness of the drilling may wear away the tungsten carbide cutting elements 386, and the second plurality of polycrystalline diamond cutting elements 384 may engage the same. One or more of the first plurality of cutting elements 386 may rotationally precede one or more of the second plurality of cutting elements 384, without limitation. Alternatively, one or more of the first plurality of cutting elements 386 may rotationally follow one or more of the second plurality of cutting elements 384, without limitation.
As a further aspect of the present invention, a casing bit of the present invention may be configured as a reamer. A reamer is an apparatus that drills initially at a first smaller diameter and subsequently at a second, larger diameter. Although the present invention may refer to “casing bit reamer,” the term “casing bit” as used herein also encompasses the structures described hereinbelow which are referred to as a “casing bit reamer.”
One type of conventional reamer, as known with respect to conventional drill bits, is a reaming assembly having a pilot drill bit at the lower longitudinal end thereof and an upper reaming structure that is centered with respect to the pilot drill bit and includes a plurality of blades to be spaced about a substantial portion of the circumference, or periphery, of the reamer. During operation, i.e., drilling, the lower pilot drill bit and the upper reaming structure rotate about a drilling axis to form a pilot borehole and a larger reamed borehole.
Turning to
Another type of conventional reamer, as is known with respect to conventional drill bits, is a bicenter bit assembly, which employs two longitudinally superimposed bit sections with laterally offset axes. The first axis is the center of the pass-through diameter, that is, the diameter of the smallest borehole the bit will pass through. This axis may be referred to as the pass-through axis. The second axis is the axis of the borehole that is formed as the bit assembly is rotated, which may be referred to as the drilling axis. Usually a first, lower and smaller diameter pilot bit section is employed to commence the drilling, and rotation of the pilot bit section is centered about the drilling axis as the second, upper and larger diameter main bit section engages the formation to enlarge the borehole, the rotational axis of the bit assembly transitions from the pass-through axis to the drilling axis when the full-diameter, enlarged borehole is drilled.
As shown in
The casing bit reamer 462 has a pass-through diameter, which is the smallest borehole that the casing bit will pass through. Accordingly, if the casing bit reamer 462 is rotated within a borehole having a smaller diameter than the reaming diameter, the casing bit reamer 462 will initially rotate generally within the smaller borehole about the central axis thereof. However, when the casing bit reamer 462 rotates about the reaming axis, the reamer wing section 463 traverses a reaming diameter, which is the diameter of the borehole that is formed as the reamer wing section 463 is rotated thereabout.
Thus, during operation which begins in a borehole that is smaller than the reaming diameter, the first, lower and smaller diameter pilot bit section 461 is employed to commence drilling a pilot-sized borehole and rotation of the pilot bit section 461 is centered about the reaming axis as the second, upper and larger diameter main bit section engages the formation to enlarge the pilot-sized borehole to the reaming diameter. Further, the rotational axis of the casing bit reamer 462 transitions from rotation within the smaller borehole to rotation about the reaming axis when the full-diameter, enlarged borehole is drilled.
Of course, an extended assembly (extended bicenter assembly) with a pilot bit at the distal or leading end thereof and a reamer assembly some distance above may also be employed by the present invention. Such an arrangement may allow the pilot bit to be changed. Further, the extended nature of the assembly may permit greater flexibility when passing through tight spots in the borehole as well as the opportunity to effectively stabilize the pilot bit so that the pilot hole and the following reamer will take the path intended for the borehole.
In addition, so-called “secondary” blades on the reamer wing to speed the transition from pass-through to drill diameter with reduced vibration and borehole eccentricity may be employed by the casing bit of the present invention, as disclosed with respect to drill bits, in U.S. Pat. No. 5,497,842, assigned to the assignee of the present invention and the disclosure of which is hereby incorporated in its entirety by reference herein. Also, the casing bit of the present invention may include a circumferentially tapered pilot stabilizer pad, as disclosed in U.S. Pat. No. 5,765,653, assigned to the assignee of the present invention and the disclosure of which is hereby incorporated in its entirety by reference herein.
The present invention also contemplates that the delivery and communication of drilling fluid may be advantageously configured in relation to a casing bit 512 of the present invention.
Nozzle 536 may comprise an erosion resistant material, such as, for instance, tungsten carbide, hardened steel, ceramic materials, diamond materials, or other hard materials exhibiting erosion resistance as known in the art. Such a configuration may allow for the fluid communicated through the nozzle 536 to exit therefrom at a relatively high velocity without damaging the nozzle 536. Of course, a nozzle 536 may also be replaceable, which may allow for selective configuration of the drilling fluid characteristics of the casing bit 512. As discussed above, it may be desirable to drill through the casing bit 512 subsequent to the casing bit 512 operating to drill a casing section into a subterranean formation. Therefore, it may be desirable to configure the erosion resistant material comprising the nozzle 536 so as to facilitate drilling therethrough. Particularly, the radial thickness, labeled “d” in
Configuring casing bit 562 with both generally radially extending blades 572 having cutting elements 565 thereon as well as rolling cones 578 may be advantageous in that the exposure of the inserts 579 disposed on rolling cones 578 in relation to cutting elements 565 disposed on the blades 572 may be substantially equalized so that in soft formations, the cutting elements 565 may more efficiently remove the formation being drilled, while in hard formations the rolling cones 578 may more effectively remove the formation being drilled. Such a configuration may provide a drilling structure suited for drilling a variety of different formation types with appropriate drilling performance in relation thereto. Alternatively, rolling cones 578 and cutting elements 565 disposed on the blades 572 may be configured according to the expected formations to be drilled. For example, the formation may be initially relatively soft (i.e., a shale), but the formation may change along the intended drilling path to a relatively hard (i.e., a limestone with stringers) formation.
As a further aspect of the present invention, a casing bit 612 may be configured to include features as described with respect to U.S. Pat. No. 6,460,631, assigned to the assignee of the present invention and the disclosure of which is incorporated in its entirety by reference herein. Alternatively, a casing bit 612 may be configured to include features as described with respect to U.S. application Ser. No. 10/266,534, which is also assigned to the assignee of the present invention and the disclosure of which is incorporated in its entirety by reference herein.
More specifically, as shown in
Apertures 633 may be disposed about the face 626 of the casing bit 612 in fluid communication with the interior of casing bit 612. Preferably, but not necessarily, as discussed above, apertures 633 may include nozzles or sleeves (not shown) disposed therein to better control the expulsion of drilling fluid from nose portion 620 into fluid courses 624 and junk slots 635 in order to facilitate the cooling of cutting elements 640 on casing bit 612 and the flushing of formation cuttings up the borehole toward the surface when casing bit 612 is in operation.
Blades 622 preferably comprise, in addition to gage region 625, an outward facing bearing surface 628, a rotationally leading surface 630, and a rotationally trailing surface 632. Therefore, as the casing bit 612 is rotated in a subterranean formation to create a borehole, rotationally leading surface 630 will be facing the intended direction of rotation of casing bit 612 while rotationally trailing surface 632 will be facing opposite, or backward from, the intended direction of casing bit 612 rotation. A plurality of cutting elements 640 may be preferably disposed along and partially within blades 622. As may be noted, cutting elements 640 proximate the longitudinal axis of the casing bit 612 may be disposed so as to be relatively sunken into or surrounded by blades 622. Further, cutting elements 640 may be positioned so as to have a superabrasive cutting face generally facing in the same direction as rotationally leading surface 630 as well as to be exposed to a certain extent beyond bearing surface 628 of the respective blade 622 in which each of cutting elements 640 is positioned. Cutting elements 640 are preferably superabrasive cutting elements known within the art, such as the exemplary PDC cutters described previously herein, and are physically secured in cutter pockets by installation and securement techniques known in the art.
Wear knots, wear clouds, or built-up wear-resistant areas 634, collectively referred to as wear knots 634 herein, may be disposed upon, or otherwise provided on bearing surfaces 628 of blades 622, with wear knots 634 preferably being positioned so as to rotationally follow cutting elements 640 positioned on respective blades 622 or other surfaces in which cutting elements 640 are disposed. Wear knots 634 may be originally molded into casing bit 612 or may be added to selected portions of bearing surface 628. As described earlier herein, bearing surfaces 628 of blades 622 may be provided with other wear-resistant features or characteristics such as embedded diamonds, TSPs, PDCs, hardfacing, weldings, and weldments, for example. Such wear-resistant features may be employed to enhance directional drilling, reduce balling, and for preventing damage to cutting elements 640 due to an excessive depth-of-cut while drilling with the casing bit 612 of the present invention.
Thus, the casing bit of the present invention may include at least one cutting element for engaging a formation having a maximum compressive strength. More specifically, the at least one cutting element may be secured to a selected portion of the face of the leading end of the casing bit, the at least one superabrasive cutter exhibiting a limited amount of cutter exposure perpendicular to the selected portion of the face of the leading end to which the at least one superabrasive cutter is secured to, in combination with the total bearing surface of the casing bit, limit a maximum depth-of-cut of the at least one cutting element into the formation during drilling.
Moreover, cutting elements and wear knots of a casing bit of the present invention may be configured to control the amount of torque experienced by the bit and an optionally associated bottom-hole assembly regardless of the effective weight-on-bit. Further, such a configuration may minimize at least one of torque fluctuations and rate-of-penetration fluctuations during drilling. Further, a casing bit so configured may include a sufficient amount of bearing surface area to contact the formation so as to generally distribute the weight of the bit against the bottom of the borehole without exceeding the compressive strength of the rock formation.
Moving to
As mentioned above, a casing bit according to the present invention may be configured with a material that may be removed therefrom by one or more of mechanical, thermal, or chemical degradation. Similarly, the body or structure of the casing bit of the present invention may be acted upon by one or more of mechanical, thermal, or chemical degradation to facilitate drilling therethrough. Accordingly, in one embodiment, a casing bit of the present invention may be configured with at least one of an explosive agent and an incendiary agent. As may be appreciated, use of an explosive agent, an incendiary agent, or both, in proximity to a casing bit may facilitate a drilling tool drilling therethrough or passing therethrough.
More specifically, as shown in
Preferably, destructive element 707 may be configured to substantially remove, destroy, perforate, degrade, weaken, or otherwise render a portion of casing bit 712 that is desired to drill therethrough to be more easily drilled. For instance, destructive element 707 may be configured to substantially remove region D1 of casing bit 712 by generating hot gases, liquids, or both, that are directed toward region D1. More specifically, for example, destructive element 707 may comprise a quantity of thermite, a mixture of powdered or granular aluminum and a metal oxide, which, of course, may be combined with other substances, such as binders, and may be configured to cause a thermite reaction. Alternatively, destructive element 707 may be configured as a tool for perforating casing, as known in the art.
Of course, cutting elements 750 generally within region D1 may be substantially removed, destroyed, perforated, degraded, weakened, or otherwise rendered more drillable. However, it may be appreciated that a majority of the cutting elements disposed on casing bit 712 within region D1 may be positioned in the region denoted by D2, because the number of cutting elements 750 may be adjusted in relation to the amount of formation removed therewith, and the volume of formation removed increases with radial distance from the center of rotation of the casing bit 712. Accordingly, destructive element 707 may be configured to substantially remove annular region D2 of casing bit 712 by generating hot gases, liquids, or both, that are directed toward annular region D2. Such a configuration may be configured to substantially remove, destroy, perforate, degrade, weaken, or otherwise render more drillable a majority of cutting elements 750 within region D1.
Also, in another embodiment, the body of a casing bit, the cutting elements affixed thereto, or both may be dissolved, degraded, abraded, weakened, or otherwise rendered more drillable prior to drilling therethrough. As shown in
Initially, container 722 may be affixed at its upper longitudinal end to casing section 760 by way of frangible elements 724 and disposed between positioning elements 730 at its lower longitudinal end. During drilling, as drilling fluid flows from the upper end 753 of casing section 760 and through apertures 721, a downward longitudinal force may be developed on container 722. However, the frangible elements 724 and apertures 721 may be sized and configured so that the frangible elements 724 will not fail in response to the flow rates of drilling fluid experienced during normal drilling conditions. Upon completion of a desired depth of drilling, the flow rate of drilling fluid may be increased to a level sufficient to fail the frangible elements 724, which may allow container 722 to be displaced longitudinally downwardly between extending positioning elements 730, as shown in
Of course, many alternatives exist for delivering a substance to the casing bit 752 by way of container 722. For instance, alternatively, barb 734 may be eliminated, while the upper wall 736 of chamber 726, the lower wall 732 of chamber 726, or both, may be configured to be frangible, so that pressure of the drilling fluid causes both to break, rupture, or otherwise perforate so as to allow a substance within chamber 726 to escape. As a further alternative embodiment, the upper wall 736 may be configured as a piston element that is releasably affixed to the chamber 726 but may be caused, by way of drilling fluid pressure, to move longitudinally downwardly within chamber 726 so as to expel a substance contained therein.
In another embodiment of substance delivery assembly 810, as shown in
As a further embodiment of a casing bit of the present invention, abrasive particles entrained within the drilling fluid may be used to erode or abrade the casing bit subsequent to drilling therewith. For instance, abrasive particles may be introduced into the drilling fluid at or near the surface of the subterranean formation. Alternatively, abrasive particles may be delivered selectively by a delivery system within the casing. For instance, turning to
In another embodiment of the present invention, a casing bit of the present invention may be mechanically configured to be frangible, weakened, or fractured preferentially, in response to forces applied thereto subsequent to drilling operations. Particularly, casing bit 852 of the present invention may include one or more recesses or grooves 855 that may cause the casing bit 852 to be frangible, weakened, or fractured preferentially. Turning to
Alternatively, the configuration as depicted in
In a further structural embodiment of a casing bit of the present invention, the body of the casing bit may be formed of fiber-reinforced composite, wherein the fiber extends in a generally circumferential fashion.
As shown in
Alternatively, as shown in
Referring back to
For example, at least one of the cutting elements 332 generally within region x1 may be affixed to the casing bit 312 by way of an adhesive. During drilling, as cutting elements 332 may be typically forced into cutting pockets (not shown) formed within the body of casing bit 312, the adhesive may exhibit sufficient strength therefor. Upon completion of drilling with casing bit 312, the cutting elements 332 within region x1 of casing bit 312 may be removed therefrom by impact loading, increasing the forces over those exerted during drilling, or heating the cutting elements 332 by drilling with reduced drilling fluid flow rates. Doing so may cause the adhesive to fail, thus allowing the cutting elements 332 within region x1 to be removed from casing bit 312. Separating the cutting elements 332 from the casing bit 312 may facilitate drilling therethrough, or may facilitate removing the cutting elements 332 from the borehole by propelling the cutting elements 332 upwardly within the borehole with drilling fluid.
The adhesive may comprise an epoxy, an acrylic, an acrylate, a phenolic, a formaldehyde, a polyurethane, a polyester, a silicone, a vinyl, a vinyl ester, a thermosetting plastic or other adhesive formulation as known in the art.
As a further alternative, affixing at least one cutting element 332 generally within region x1 by way of soldering may facilitate removal thereof after drilling, particularly by heating the cutting elements 332 by drilling with reduced drilling fluid flow rates. As used herein, “brazing” refers to affixation formed by way of at least partially melting a material at a temperature of about 1000° Fahrenheit or higher, while “soldering” refers to affixation formed by way of at least partially melting a material at a temperature of between about 400° Fahrenheit to about 1000° Fahrenheit. However, the ranges of soldering and brazing may overlap, above and below 1000° Fahrenheit. In further detail, soldering material (i.e., a solder) may typically comprise tin, lead, silver, copper, antimony, or as otherwise known in the art. Also, solder used to affix at least one cutting element 332 generally within region x1 may preferably comprise a eutectic alloy.
In a further alternative, at least one cutting element may be affixed to a casing bit by way of so-called electrically disbonding adhesive. For instance, U.S. Pat. No. 6,620,380 to Thomas et al., the disclosure of which is incorporated in its entirety by reference herein, discloses an electrically disbonding material which may be configured as an adhesive, having a lap shear strength in the range of 2000-4000 psi. Further, the bond between the disbondable composition and a substrate may be weakened in a relatively short time by the flow of electrical current across the bondline between the substrate and the composition. Accordingly, at least one of the cutting elements 332 generally within region x1 may be affixed to the casing bit 312 by way of an electrically disbonding material. During drilling, as cutting elements 332 may be typically forced into cutting pockets (not shown) formed within the body of casing bit 312, the electrically disbonding material may exhibit sufficient strength therefor. Upon completion of drilling with casing bit 312, the at least one cutting element 332 within region x1 of casing bit 312 may be removed therefrom by causing an electric current to flow across the electrically disbonding material. Doing so may cause the electrically disbonding material to fail or weaken, thus allowing the cutting elements 332 within region x1 to be removed from casing bit 312.
More particularly, an electric current may flow across the electrically disbonding material by applying a voltage between the casing bit and a cutting element. For instance,
The present invention also contemplates that drilling fluid sleeves or nozzles may also be affixed to and selectively released from a casing bit by way of electrically disbonding material. More generally, materials that may be difficult to drill through may be affixed to and selectively released from a casing bit.
Alternatively,
In yet another aspect of the present invention, referring to
During drilling, the cutting element 332 may proceed into a formation 348 to remove cuttings therefrom. As may be appreciated, head portion 337 of fastening element 338 may be sized to allow the cutting surface 335 to engage the formation 348 at a desired depth-of-cut without contacting the formation 348 itself. However, the head portion 337 may be configured to contact the formation 348 in response to wear exhibited by the cutting element 332, in response to a depth-of-cut that causes such contact, or by design. After drilling, a drilling tool (not shown) may be disposed to drill into the inner profile 316 of casing bit 312. The drilling tool (not shown) may proceed generally oppositely to the direction of axis y. Axis y is shown on
In another embodiment wherein a cutting element may be configured to become separated from a casing bit 312, a cutting element 332 may be configured with “stud-type” body 354 as shown in
As yet another alternative, referring to
In yet another aspect of the present invention, at least two casing bits of different diameter and having associated casing sections may be assembled to form a drilling assembly for drilling into subterranean formations, wherein radially adjacent casing sections are selectively releasably affixed to one another and wherein the at least two casing bits and casing sections are arranged in a telescoping relationship. Such a configuration may reduce the time needed to dispose the casing sections that are attached to each larger and smaller casing bit into the borehole.
For example, as shown in
Therefore, during operation, torque and WOB may be applied to casing bit 914 through casing section 906. Alternatively, torque and WOB may be applied to casing bit 914 by way of casing section 908 and through frangible elements 918. As may be appreciated, when the casing bits 914 and 916 are structurally coupled to one another, torque, WOB, or both, may be transmitted therebetween. In addition, the fluid ports or apertures between each of the casing bits 914 and 916 may be coupled so that drilling fluid may be delivered through the interior of casing bit 916 to casing bit 914. Alternatively, drilling fluid may be delivered through annulus 924, while the ports or apertures of casing bit 916 may be plugged or blocked. Thus, many alternatives are possible for delivering drilling fluid to any of casing bits 914 and 916.
As shown in
Alternatively, an assembly of two of more casing sections configured in a telescoping relationship may be drilled into a subterranean formation by a drilling tool disposed at the leading end thereof. Specifically, as shown in
As the drilling assembly proceeds into the formation, radially adjacent smaller casing sections may be unlatched from radially adjacent larger casing sections and extended therefrom. Of course, frangible elements (not shown) as described hereinabove (
Additionally, an assembly of two of more casing sections configured in a telescoping relationship may be drilled into a subterranean formation by a casing bit disposed at the leading end thereof. As shown in
In a further aspect of the present invention, at least one reaming blade or structure of a casing bit reamer, as described above, may be movable or expandable. U.S. application Ser. No. 10/624,952, now U.S. Pat. No. 7,036,611, assigned to the assignee of the present invention, the disclosure of which is incorporated in its entirety by reference herein, discloses an expandable reamer apparatus for enlarging boreholes while drilling and methods of use that may be actuated by drilling fluid flowing therethrough. Further, U.S. Pat. No. 6,360,831 to Åkesson et al. discloses a conventional borehole opener comprising a body equipped with at least two hole-opening arms having cutting means that may be moved from a position of rest in the body to an active position by way of a face thereof that is directly subjected to the pressure of the drilling fluid flowing through the body.
Referring to
Expandable casing bit reamer 1100 is shown, in a schematic side cross-sectional view, in an expanded state in
However, other mechanisms for expanding an expandable casing bit reamer, for instance, tapered surfaces, may be forced against one another to cause the expansion of movable blades. For instance,
More specifically, as drilling fluid passes through sleeve 1140, a pressure differential caused by drilling fluid flow through sleeve 1140, specifically orifice 1150 may cause a downward longitudinal force to be applied to sleeve 1140. A collet, shear pins, or other frangible element (not shown) may be used to resist the downward longitudinal force until the shear point of the releasable member is exceeded. Thus, the downward force generated by the drilling fluid moving through the reduced cross-sectional area orifice 1150 may cause a friable or releasable element to release the sleeve 1140 and allow the sleeve 1140 to move downward to cause tapered surface 1172 of sleeve 1140 to matingly engage the tapered surfaces 1127 and 1129 of blades 1112 and 1114, respectively. Such mating engagement may force blade 1112 against biasing elements 1124 and 1126, and may force blade 1114 against biasing elements 1128 and 1130. Blade 1112 may compress biasing elements 1124 and 1126 sufficiently to matingly engage the inner radial surface of retention member 1116, while blade 1114 may compress biasing elements 1128 and 1130 sufficiently to matingly engage the radial inner surface of retention member 1120. Thus, expandable casing bit reamer 1110 may be expanded to ream a borehole. Alternatively, apertures or ports (such as 1142 shown in
In a further aspect of the casing bit of the present invention, at least one sensor configured for measuring a condition of drilling, a condition of the casing bit, or a formation characteristic may be included by the present invention. Particularly, as to measurements concerning the casing bit, revolutions per minute, rate-of-penetration, torque-on-bit, weight-on-bit, strain measurements at one or more surface of the casing bit may be measured, and temperatures at one or more locations within or near the casing bit may be measured. As to the formation being drilled, formation hydrostatic pressure, pore pressure, temperature, azimuth, inclination, resistivity, gamma emissions, caliper, or other formation or borehole characteristics may be measured. Further, a casing bit of the present invention may include a sensor or a sensor may be positioned near the casing bit of the present invention. Further, a measurement obtained via a sensor may be stored, communicated to operators thereof, or both. Such a communication system may include fiber-optic transmission, electromagnetic telemetry, wired pipe, or as otherwise known in the art. U.S. Pat. Nos. 6,626,251, 6,571,886, 6,543,312, and 6,540,033, each assigned to the assignee of the present invention, the disclosure of each of which is incorporated in its entirety by reference herein, each disclose a method and apparatus for monitoring and recording of the operating condition of a conventional downhole drill bit during drilling operations.
In another exemplary embodiment of a casing bit according to the present invention, cutting elements may be arranged and disposed within discrete cutting element retention structures. Put another way, the casing bit of the present invention may include at least one discrete cutting element retention structure for affixing a cutting element within. Accordingly, the casing bit of the present invention may not include generally radially extending blades. Rather, the casing bit of the present invention may be configured to carry cutting elements by way of discrete cutting element retention structures extending from the nose portion thereof.
As shown in
In another embodiment of a casing bit of the present invention, a casing bit of the present invention may be configured for percussion, “percussion” meaning interrupted contact between the casing bit and the formation. Typically, percussion drilling may be accomplished by varying the longitudinal position of the casing bit as it is rotated. Thus, the casing bit may repeatedly oscillate between contacting and not contacting the formation.
More specifically, as shown in
It should, however, be understood that the bit body design of casing bit 1312 is not limited to percussion inserts installed thereon. Put another way, the casing bit of the present invention may comprise a bit body that does not include blades, but rather has a substantially symmetrical profile, with respect to the longitudinal axis thereof, that forms the outer surface of the casing bit and cutting elements may be affixed thereto. For instance, polycrystalline diamond cutting elements may be installed upon a bit body design as shown in
Further, stud-type cutting elements 1342 may be sized and configured to fit within associated recesses 1340 formed in casing bit 1313. As known in the art, stud-type cutting elements 1342 may be press-fit, brazed, welded, or any combination thereof within associated recesses 1340 of casing bit 1313. Further, alignment groove 1341 may be used to orient each of stud-type cutting elements 1342 within associated recesses 1340, also as known in the art. Of course, alternatively, pockets, as shown in
Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the present invention, but merely as providing illustrations of some exemplary embodiments. Similarly, other embodiments of the invention may be devised which do not depart from the spirit or scope of the present invention. Features from different embodiments may be employed in combination. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions, and modifications to the invention, as disclosed herein, which fall within the meaning and scope of the claims are to be embraced thereby.
This application is a continuation of U.S. patent application Ser. No. 12/129,308, filed May 29, 2008, now U.S. Pat. No. 8,006,785, issued Aug. 30, 2011, which is a divisional of application Ser. No. 10/783,720, filed Feb. 19, 2004, now U.S. Pat. No. 7,395,882, issued Jul. 8, 2008, the disclosure of each of which applications is incorporated by reference herein in its entirety.
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