Two-part bit wiring assembly

A downhole drilling assembly may comprise a sub secured between a drill string and a drill bit. The sub may comprise a cavity with a chassis housed therein. The drill bit may also comprise a cavity with an extender housed therein. This extender may provide access for various types of communication to reach into the drill bit's cavity. Several pairs of interfacing exchange surfaces may allow for communication (e.g. passing electrical, hydraulic, optical or electromagnetic signals) between these various elements. One pair of interfacing exchange surfaces, between the drill string and the chassis, may allow for communication regardless of relative rotational orientation. Two other pairs of interfacing exchange surfaces, one between the chassis and the extender and another between the extender and the drill bit, may require a specific rotational orientation for communication.

BACKGROUND

When exploring for or extracting subterranean resources, such as oil, gas, or geothermal energy, and in similar endeavors, it is common to form boreholes in the earth. Such boreholes are often formed by engaging the earth with a rotating drill bit capable of degrading tough earthen materials. As rotation continues the borehole may elongate and the drill bit may be fed into it on the end of a drill string.

At times it may be desirable to take measurements or perform various functions within a borehole while drilling is in progress. It is believed that certain measurements and functions are most effective when taken or performed as close as possible to an end of a drill string, or on a drill bit itself. Drill bits of this type, however, often experience significant wear and damage while drilling, due to the harsh conditions. Worn or damaged drill bits often require replacement which can be expensive and time consuming. Instrumenting drill bits to take measurements or perform functions may significantly add to replacement expense and complexity.

One of the more complex aspects of instrumenting such a drill bit is providing a mechanism for communicating back and forth across the connection between the drill bit and the drill string. Such connections are typically made by threading a drill bit to a drill string amid an often dirty and hectic drilling operation. Given the disorder of such conditions it may be difficult to certify the final positions, either rotationally or axially, of the drill bit relative to the drill string. Any communication mechanism spanning such a connection must be robust and functional regardless of orientation.

Another feature adding complexity to drill bit instrumentation is the externally-threaded protrusions and the internally-threaded cavities that commonly form either side of the connection. In particular, passing communications into a cavity may be difficult as access may be restricted by space constraints. Thus, a mechanism capable of passing communications across a drill-string-to-drill-bit connection independent of specific rotational orientation while providing access inside a threaded cavity may prove useful in instrumenting a drill bit.

BRIEF DESCRIPTION

A downhole drilling assembly may comprise a sub secured between a drill string and a drill bit. This sub may comprise a cavity formed therein and a chassis may be housed within the cavity. The drill bit may also comprise a cavity formed therein and an extender may be housed within this cavity. This extender may contact the drill bit at a base of this cavity and extend to within two inches of a mouth of the cavity. This extender may provide access for various types of communication to reach into the drill bit's cavity.

Several pairs of interfacing exchange surfaces may allow for communication (e.g. passing electrical, hydraulic, optical or electromagnetic signals) between these various elements. One pair of interfacing exchange surfaces, between the drill string and the chassis, may allow for communication regardless of relative rotational orientation. Two other pairs of interfacing exchange surfaces, one between the chassis and the extender and another between the extender and the drill bit, may require a specific rotational orientation for communication.

The first pair of interfacing exchange surfaces may allow for communication regardless of rotational orientation. Meanwhile, the extender may allow for access within the cavity of the drill bit. The combination may allow for measurements to be taken or functions to be performed on the drill bit.

DETAILED DESCRIPTION

Referring now to the figures,FIG. 1shows an embodiment of a subterranean drilling operation of the type commonly used to form boreholes in the earth. Specifically, a drill bit110, capable of degrading tough subterranean materials, may form part of a downhole drilling assembly111. The drilling assembly111may be attached to one end of a drill string114suspended from a derrick112. While a land-based derrick112is depicted, comparable water-based structures are also common. Such a drill string114may be formed from a plurality of drill pipe sections fastened together end-to-end, as shown, or, alternately, a flexible tubing. As the drill bit110is rotated, either with torque from the derrick112passed through the drill string114or by a downhole motor, it may engage and degrade a subterranean formation116to form a borehole118therethrough.

FIG. 2shows an embodiment of a downhole drilling assembly211comprising a drill string214secured to a sub220, and the sub220further secured to a drill bit210. A continuous fluid channel225may pass axially through the drill string214and sub220, and into the drill bit210. While any of a variety of types of drill bits may serve in this role and function with the novel elements described herein, the present embodiment drill bit210comprises a plurality of blades221, spaced around a central axis, protruding from one end thereof. A plurality of cutting elements222may be exposed on leading edges of each of the blades221. Such cutting elements222may comprise a superhard material (i.e. a material comprising a Vickers hardness test number exceeding 40 gigapascals) capable of degrading tough subterranean materials. When the drill bit210is rotated about this axis, the blades221may engage an earthen formation allowing the cutting elements222to bore a hole therein.

While it is common for drill bits used in downhole drilling to comprise a threaded protrusion extending therefrom for attachment, the drill bit210of the embodiment shown comprises an internally-threaded cavity223positioned axially opposite the blades221and cutting elements222. An extender224may be seated within this cavity223. This may allow for access deep into the drill bit210. When seated, this extender224may comprise a proximal end that contacts a nadir of the drill bit210cavity223. The cavity223may be formed so deep into the drill bit210that the cutting elements222axially span this proximal end and nadir. The extender224may also comprise and a distal end that extends to within 2 inches of a mouth of the cavity223. It is believed that this positioning relative to the cavity's223mouth may allow for relatively easy access to this distal end. In the embodiment shown, the extender224comprises a generally conical exterior shape. This conical shape may be widest toward the proximal end and narrow as it approaches the distal end. Additionally, the fluid channel225may pass axially through the extender224.

The sub220may be secured to the drill bit210via an externally threaded protrusion226that may be inserted into the cavity223of the drill bit210and mate with the internal threads therein. These threads may be designed to cease rotation and lock into place at a fixed rotational and axial position. Threading of this protrusion226into the cavity223may act to retain the extender224within the cavity223. Similarly, unthreading of the protrusion226and cavity223may release the extender224such that it may be interchangeable with an alternate extender.

The sub220may also comprise a cavity227disposed therein comprising internal threads spread over at least a section thereof. A chassis228, comprising a generally tubular structure, may be housed within this cavity227. The drill string214may comprise an externally threaded protrusion230that may be inserted into the cavity227of the sub220and mate with the internal threads therein. These threads may be designed to cease rotation and lock into place at a fixed rotational and axial position. Threading of this protrusion230into the cavity227may act to both secure the drill string224to the sub220and retain the chassis228within the cavity227. While, unthreading the drill string224from the sub220may allow for both the sub220and the chassis228to be interchangeable with an alternate sub or chassis (or both) of different axial length. The fluid channel225may pass axially through the chassis228.

Pairs of interfacing exchange surfaces, at each of the intersections between the drill bit210, the sub220and the drill string214, may allow for various types of communications to occur between these elements. Mating of each of these pairs of interfacing exchange surfaces, in a manner allowing for communication, may naturally result from the physical attachment of the drill string214to the sub220and the sub220to the drill bit210without additional action. This may allow for such mating to be accomplished as part of the activities already commonly performed as part of a drilling operation.

A first pair of interfacing exchange surfaces231may connect the drill string214to the chassis228within the sub220; specifically, one of the first pair of interfacing exchange surfaces231may be disposed on a tip of the protrusion230formed on one end of the drill string214. This first pair of interfacing exchange surfaces231may allow for communication between the drill string214and the chassis228regardless of where they land in rotational orientation relative to each other. This independence from reliance on relative rotational orientation for communication may provide an allowance for play in the physical attachment of the drill string214to the sub220; which often occurs under dirty and hurried conditions at a drilling location.

A second pair of interfacing exchange surfaces232may connect the chassis228to the extender224within the drill bit210. And a third pair of interfacing exchange surfaces233may connect the extender224to the drill bit210, in which it is housed. These third interfacing exchange surfaces233may be positioned inside of internal threads within the cavity223of the drill bit210. The extender224may be long enough axially that the cutting elements222, exposed on an exterior of the drill bit210, axially span this connection between the extender224and the drill bit210. As opposed to the first pair, the second and third pairs of interfacing exchange surfaces232,233may be fixed together in specific relative rotational orientations. In some embodiments, rotational orientation may be maintained by forming stab style connections. Further unlike the first pair, these orientation-specific interfacing exchange surfaces232,233may be connected under cleaner and calmer conditions, removed from the drilling location, that may generally lead to more accurate positioning. Additionally, the extender224may aid in bringing such connections out of the cavity223of the drill bit210that could restrict access. Speaking of the extender224, one side of each of the second and third pairs of interfacing exchange surfaces232,233may be connected to one another via at least one communication conduit235passing through the extender224.

One side of each of the first and second pairs of interfacing exchange surfaces231,232may be connected to one another via at least one communication conduit234passing through the chassis228. The chassis228may further comprise various electronics229disposed circumferentially about an exterior surface thereof. These electronics229may be housed within a pressure chamber formed between the chassis228and the sub220. These electronics229may also be connected to at least one side of the first and second pairs of interfacing exchange surfaces231,232via the communication conduit234described previously. As the sub220may be longer than the drill bit210, as shown in this embodiment, the size of these electronics229need not be limited by the length of the drill bit210.

A pad236may be radially extendable or retractable from a side of the drill bit210via hydraulic pressure applied through the various communication conduits234,235described previously. Extension of this pad236may be to perform any of a variety of downhole functions, such as steering or stabilization. Specifically, as the pad236extends it may push against an interior of a borehole (not shown) through which the drill bit210is traveling to change its direction of travel or hold it in place. Activation of such a downhole function may be controlled by the electronics229disposed downhole around the chassis228.

FIGS. 3-1 and 3-2show additional embodiments of downhole drilling assemblies311-1and311-2respectively. Each of the downhole drilling assemblies311-1,311-2may comprise a drill string314-1,314-2secured to a sub320-1,320-2, which is further secured to a drill bit310-1,310-2. Further, each embodiment comprises a mechanism, in addition to threads (hidden) described previously, for securing the attachment of the sub320-1,320-2to its respective drill bit310-1,310-2. This additional security may be to prevent accidental or unintentional removal of the drill bit310-1,310-2from the sub320-1,320-2while attempting to remove the sub320-1,320-2from its respective drill string314-1,314-2.

Specifically,FIG. 3-1shows an embodiment of a downhole drilling assembly311-1comprising a weld or adhesive340-1securing the drill bit310-1to the sub320-1.FIG. 3-2shows an embodiment of a downhole drilling assembly311-2comprising a plurality of mechanical fasteners341-2that may each be threaded radially into the sub320-2to further secure the drill bit310-2to the sub320-2. One of these mechanical fasteners341-2is shown partly removed to reveal the threads. Additionally, each of these mechanical fasteners341-2may comprise an exposed head comprising a unique geometry requiring a specialized tool for removal.

Each of the first, second and third pairs of interfacing exchange surfaces may allow for various types of communication. For example, any of the pairs of interfacing exchange surfaces may allow for the exchanging of electrical, hydraulic, optical and/or electromagnetic signals; although, they may do this in different ways. Specifically, the first pair of interfacing exchange surfaces, between the drill string and the chassis, may allow for this communication independent of any specific rotational orientation.FIG. 4shows one possible embodiment of a rotationally-independent pair of interfacing exchange surfaces. Particularly, a threaded protrusion440may be received and secured within a threaded cavity441. This protrusion440comprises one interfacing exchange surface442disposed on a distal tip thereof. In the embodiment shown, this interfacing exchange surface442is capable of exchanging power and data, via electricity and hydraulic fluid, with another interfacing exchange surface443housed within the cavity441. While this embodiment shows electrical and hydraulic based communication, other media such as optical or electromagnetic signals are also possible.

With respect to electricity, the interfacing exchange surface442comprises an inductive ring444that may sit adjacent another inductive ring445of the other interfacing exchange surface443. While adjacent, electrical signals passing through the one inductive ring444may be communicated to the other inductive ring445via inductive coupling. These electrical signals may be passed regardless of relative rotational orientation of the pair of interfacing exchange surfaces442,443.

With respect to hydraulic fluid, the interfacing exchange surface442comprises two ducts446exposed thereon that may conduct fluid to two other ducts447exposed on the other interfacing exchange surface443. These sets of two ducts446,447may allow for hydraulic power and/or pulsing data to be transmitted between the pair of interfacing exchange surfaces442,443. Two nearly-semiannular grooves448may also be positioned on the interfacing exchange surface448inside the inductive ring444discussed previously, one adjacent each of the two ducts446exposed thereon. These nearly-semiannular grooves448may allow fluid to flow therethrough from the two ducts446of the protrusion440to the two ducts447of the cavity441in a wide span of relative rotational orientations. As can be seen, only one of a pair of interfacing exchange surfaces needs such grooves for this type of rotationally independent fluid transfer.

In the embodiment shown, the ducts447are positioned directly opposite each other, or 180 degrees apart, however, this spacing is not necessary. Specifically, similar ducts may be spaced at different angular positions in different embodiments. Further, threads of the protrusion440may be roughly timed to threads of the cavity441such that, even under imprecise conditions, the ducts447are not blinded by blanks between the nearly-semiannular grooves448.

Other pairs of interfacing exchange surfaces, such as the second pair between the chassis and the extender and the third pair between the extender and the drill bit, may require a specific rotational orientation for communication.FIG. 5shows one possible embodiment of a rotationally-fixed pair of interfacing exchange surfaces. One interfacing exchange surface542may comprise a plurality of pins550protruding therefrom. Another interfacing exchange surface543may comprise a plurality of sockets551into which the pins550may insert when the two interfacing exchange surfaces542,543are paired with one another. Insertion of the pins550into the sockets551may align a plurality of ducts546exposed on the one interfacing exchange surface542with a matching plurality of ducts547exposed on the other interfacing exchange surface543. In such a configuration, fluid may flow between the two sets of ducts546,547to transmit hydraulic power and/or pulsing data between the interfacing exchange surfaces542,543when rotationally aligned in a specific orientation. Further, the pins550and sockets551may be wired to transmit electrical power and/or data.

Whereas the present discussion has referenced the figures attached hereto it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the scope and spirit of the present disclosure.