Continuous Sampling Drill Bit

This is a continuation of U.S. patent application Ser. No. 17/614,728, filed Nov. 24, 2022, which is a U.S. National Phase Application of International Application No. PCT/US2021/033612, filed May 21, 2021, the entire disclosures of which are hereby incorporated by reference.

Conventionally, core sampling requires a wireline assembly for retrieving a cylindrical core sample drilled by a core sampling bit. Such core sampling is a time consuming and intensive process that requires complex wireline tooling. Accordingly, a need exists for a sampling method that eliminates wireline tooling and does not require a need to stop drilling to separate samples from the formation or to retrieve samples. Continuous sampling methods that use percussive pneumatic hammers are limited to non-water-bearing (dry) formations, require air circulation, have high energy consumption, and suffer from further limitations of percussive drill bits.

Described herein, in various aspects, is a drill bit drill bit having a central axis. The drill bit can comprise a shank defining an inner bore and a crown having a cutting face. The crown can define an outer operative circumference. The crown can comprise a core-receiving slot in communication with the inner bore of the shank. At least one peripheral slot can be in communication with the inner bore of the shank. The at least one peripheral slot can be positioned radially between the core-receiving slot and the outer operative circumference of the crown. The crown can further comprise at least one face channel. Each face channel of the at least one face channel can extend between and be in fluid communication with the core-receiving slot and a respective peripheral slot of the at least one peripheral slot. A base portion can be positioned within the core-receiving slot. The base portion can define a breaking surface. At least a portion of the breaking surface, or a plane tangential thereto, can be oriented at an oblique angle to the central axis. The at least one peripheral slot can be configured to receive fluid moving in a distal direction toward the cutting face of the crown. The at least one face channel can be configured to deliver fluid from the at least one peripheral slot to the core-receiving slot.

A drilling assembly can comprise an outer tube and an inner tube received within the outer tube so that the inner tube and the outer tube cooperate to define an annular space. The shank of the drill bit can be threadedly coupled to the outer tube. The drilling assembly can further comprise a sub that provides fluid communication between, the core receiving slot of the crown of the drill bit and the inner tube.

A method can comprise advancing the drilling assembly into a formation to form drilling cuttings and core segments. The method can further comprise pumping fluid through the annular space and collecting the core segments returning through the inner tube.

In another aspect, a drill bit can have a central axis. The drill bit can comprise a shank defining an inner bore and a crown having a cutting face. The crown can define an outer operative circumference. The crown can comprise a core-receiving slot in communication with the inner bore of the shank. The crown can further comprise at least one face channel, wherein each face channel of the at least one face channel extends between and is in communication with the core-receiving slot and the outer operative circumference of the crown. A base portion can be positioned within the core-receiving slot. The base portion can define a breaking surface. At least a portion of the breaking surface, or a plane tangential thereto, can be oriented at an oblique angle to the central axis. The at least one face channel can be configured to receive fluid flowing distally along the outer surface of the crown and deliver fluid from the outer surface of the crown to the core-receiving slot.

Additional advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. It is to be understood that this invention is not limited to the particular methodology and protocols described, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention.

Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

As used herein the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. For example, use of the term “a crown portion” can refer to one or more of such crown portions, and so forth.

All technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs unless clearly indicated otherwise.

As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

As used herein, the term “at least one of” is intended to be synonymous with “one or more of.” For example, “at least one of A, B and C” explicitly includes only A, only B, only C, and combinations of each.

Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. Optionally, in some aspects, when values are approximated by use of the antecedent “about,” it is contemplated that values within up to 15%, up to 10%, up to 5%, or up to 1% (above or below) of the particularly stated value can be included within the scope of those aspects. Similarly, if further aspects, when values are approximated by use of “approximately,” “substantially,” and “generally,” it is contemplated that values within up to 15%, up to 10%, up to 5%, or up to 1% (above or below) of the particularly stated value can be included within the scope of those aspects. In still further aspects, when angular relationships (e.g., “parallel” or “perpendicular”) are approximated by use of “approximately,” “substantially,” or “generally,” it is contemplated that angles within 15 degrees (above or below), within 10 degrees (above or below), within 5 degrees (above or below), or within 1 degree (above or below) of the stated angular relationship can be included within the scope of those aspects.

The word “or” as used herein means any one member of a particular list and also includes any combination of members of that list.

As used herein, the term “proximal” refers to a direction toward a drill rig or drill operator and generally opposite a direction of drilling (and away from a formation or borehole), while the term “distal” refers to a direction away from the drill rig or drill operator and generally in the direction of drilling (and into a formation or borehole).

It is to be understood that unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; and the number or type of aspects described in the specification.

The following description supplies specific details in order to provide a thorough understanding. Nevertheless, the skilled artisan would understand that the apparatus, system, and associated methods of using the apparatus can be implemented and used without employing these specific details. Indeed, the apparatus, system, and associated methods can be placed into practice by modifying the illustrated apparatus, system, and associated methods and can be used in conjunction with any other apparatus and techniques conventionally used in the industry.

According to various aspects, the devices, systems, and methods disclosed herein can be used in continuous sampling of a formation. That is, formation samples, comprising relatively small cuttings and/or larger core segments (further described herein), can be retrieved as the formation is drilled using reverse circulation. The formation samples can be tested and inspected in order to determine the makeup and various other information regarding the formation (e.g., information conventionally determined via core samples retrieved via conventional wireline). In contrast to conventional wireline core sampling, the disclosed devices, systems, and methods enable samples to be collected while drilling, greatly increasing sampling rate. Additionally, it is contemplated that the samples can be associated with the depth at which they were collected. That is, the time delay between the depth at which the samples were removed from the formation and subsequently pumped from the proximal end of the borehole and collected can be accounted for (e.g., using a known rate of travel of the samples at a given flow rate).

Disclosed herein, with reference to, is a drill bit for use with a drilling systemthat includes a drill head. The drill headcan be coupled to a mastthat, in turn, is coupled to a drill rig. The drill headcan be configured to have one or more tubular threaded memberscoupled thereto. Tubular memberscan include, without limitation, drill rods, casings, and down-the-hole hammers. Optionally, in some aspects, use of embodiments disclosed herein can eliminate a need for down-the-hole hammers. For ease of reference, the tubular memberswill be described herein as drill string components. Each drill string componentcan in turn be coupled to additional drill string componentsto form a drill or tool string. In turn, the drill stringcan be coupled at a distal end to a drilling tool, such as a rotary drill bit, impregnated, core sampling drill bit, or percussive bit, configured to interface with the material, or formation, to be drilled. The drilling toolcan form a boreholein the formation. According to some implementations of the present invention, the drilling toolcan include a reverse circulation continuous sampling drill bit, such as those depicted and described in relation to.

In reverse circulation systems, a pressurized fluid is pumped down the borehole. The fluid can be pumped down an outer annulus, such as, for example, a space between the boreholeand the outer wall of the drill string. The fluid can then return through an interior of the drill string. In reverse circulation drilling, the returning fluid can provide fluid pressure to move certain components or materials in a proximal direction along (optionally, up) the drill string. As disclosed herein, the returning fluid can carry core sample bits in a proximal direction along (optionally, up) the drill string and to the borehole outlet. Further aspects of reverse circulation systems are disclosed in International Application No. WO 2018/152089 to BLY IP INC., filed Feb. 13, 2018, which is hereby incorporated herein in its entirety. The reverse circulation system can exclude air circulation, which can be beneficial in water-bearing formations in which air cannot be circulated. Because fluid can be passed around the outer wall of the drill string, dual-tube drill strings may not be required. That is, in some aspects, and as further described herein, the drill string may only comprise a single tube that is coupled to the drill bit. However, according to further aspects, it is contemplated that dual-tube drill strings can be used under conditions where the ground/formation is not suitable for acting as an outer wall of a conduit through which fluid can be pumped (e.g., porous or soft ground conditions).

In various aspects and with reference to, the drill bitcan have a central axis. The drill bitcan comprise a shankdefining an inner bore. The shankcan define at least one thread(e.g., one or more female threads) that are configured to couple to the drill string(). Optionally, referring also to, the shankcan define one or more through-holesthat extend radially outwardly from the inner boreto an outer circumferential surfaceof the shank. Said through-holescan optionally extend at an acute angle relative to the central axis so that the through-holes have outlets at the outer circumference that are distal of the inlets at the inner bore, thereby directing flow toward the distal end of the drill bit.

The drill bitcan further comprise a crown, which can have a cutting facethat defines an outer operative circumference(). An operative circumference can be defined as a continuous pathway (e.g., a circular or round pathway), formed within a plane that is perpendicular to the central axis, by tracing and connecting respective portions of the inner surfaces or outer surfaces of the crown. Thus, the operative circumference simulates a boundary or perimeter that would exist if the inner or outer surface of the crown extended continuously (without interruption) over 360 degrees. Accordingly an outer operative circumference can circumscribe an outer surface of the crown, and an inner operative circumference can circumscribe one or more inner surfaces of the crown.

The crowncan comprise a core receiving slotin communication with the inner boreof the shank. The core receiving slotcan define an inner operative circumference. That is, as the bit rotates, the cutting faceof the drill bitcan define an inner area that the cutting facedoes not engage. Accordingly, as the drill bitadvances into a formation, a portionof the formation within the inner operative circumference can remain intact with the formation and extend inwardly into the core receiving slot. In some aspects, the area of the inner operative circumferencecan range from less than about 5 square centimeters to about 18 square centimeters in cross section. In still further aspects, the inner operative circumferencecan have a diameter ranging from about 5 mm to about 40 mm, or from about 8 mm to about 25 mm. In further aspects, the inner operative circumference can have a diameter of less than 5 mm or greater than 40 mm.

Referring to, the crown can define a base portionpositioned within the core receiving slot. Optionally, as further disclosed herein, the base portioncan extend between opposing sides of the core-receiving slot. The base portioncan define a breaking surface. At least a portion of the breaking surface can be oriented at an oblique angle to the central axis. In this way, the breaking surface can be configured so that as the portionof the formation within the core receiving slot (core sample) biases against the breaking surface, the breaking surface can apply a stress to the core sample to cause it to break, thereby providing for collection of a core segment. For example, referring to, in some optional aspects, the breaking surfacecan intersect a first plane including the central axisand a first transverse axisat a line. The line can form a break angle, a, with the first transverse axis. The break angle can be between about 15 and about 45 degrees, or about 30 degrees. Referring to, in some optional aspects, the breaking surfacecan intersect a second plane including the central axisand a second transverse axisthat is perpendicular to the first transverse axisat an arc having a proximal concavity (a concavity that faces in a proximal direction). Thus, in some aspects, across the break surface, no plane that is tangential to the break surface can be perpendicular to the central axis. Optionally, in some aspects, the break surfacecan have a conical shape with an apex. In some aspects, the base portioncan have an apexthat corresponds to a distal-most point on the base portion. In some aspects, the apexcan be radially spaced from the central axis. Thus, as the cylindrical core sampleengages the base portion, the cylindrical core sample can undergo a lateral force that causes the core sample to break off. Optionally, in these aspects, the apexcan be spaced from the central axisof the drill bitrelative to the first transverse axis. Optionally, in another aspect, the apexcan be spaced from the central axisof the drill bitrelative to the second transverse axis. In further aspects, the break surfacecan be planar and oriented at an acute angle relative to the central axis.

The apexcan be spaced from the central axisby at least the radius of the inner operative circumference. In exemplary aspects, the apex() of the breaking surfaceof the base portioncan be spaced from the cutting facealong the central axisof the drill bitby between 0.1 inches and 0.5 inches (e.g., about 0.21 inches) along the second axisand between 0.1 inches and 0.5 inches (e.g., about 0.315 inches). Optionally, in one exemplary aspect, the axial distance between the base portionand the cutting facealong the central axiscan vary moving across the base portion relative to the first transverse axis. In a further exemplary aspect, the axial distance between the base portionand the cutting facealong the central axiscan vary moving across the base portion relative to the second transverse axis. In yet another exemplary aspect, the axial distance between the base portionand the cutting facerelative to the central axiscan vary moving across the base portion along both the first transverse axisand the second transverse axis. Optionally, in exemplary aspects, said axial distance can range from about 1 inch to about 2.5 inches, or from about 1.3 inches to 2.3 inches, or about 1.96 inches, or from 0.25 to 1.5 inches, or from 0.35 inches to about 1.22 inches.

In optional contemplated aspects, at least a portion of the breaking surfacecan be substantially planar, and at least a portion of the breaking surface can be curved (either distally or proximally). In other contemplated aspects, the breaking surfacecan have a compound curvature, with a first portion of the breaking surface having a first radius of curvature and at least a second portion of the breaking surface having a second radius of curvature different from the first radius of curvature. For example, the breaking surfacecan be conical.

At least one conduit(e.g., a pair of conduitsdisposed on opposing sides of the breaking surfacealong the first transverse axis) can communicate the core segmentsto the inner boreof the shank. Accordingly, the conduitscan have minor dimensions that are greater than the major dimensions of the core segmentsto inhibit clogging. It is contemplated that the major dimensions of the core segments can optionally be less than the length from the cutting face to the breaking surface (e.g., about 1 inch or less). The core segmentthat has broken off can be centrifugally ejected radially outwardly from the base portion. The cylindrical core samplecan optionally be further broken apart into smaller pieces that pass through the conduits.

The crowncan further comprise one or more peripheral slotsin communication with the inner boreof the shank. In some aspects, the crown can comprise only one single peripheral slot. Each peripheral slotcan be positioned radially between the core-receiving slotand the outer operative circumference of the crown. In further aspects, the crown can comprise a plurality of peripheral slots(optionally, two, three, four, at least three, at least four, or more peripheral slots).

The crowncan comprise one or more face channels. Each face channelcan extend between, and be in fluid communication with, a respective peripheral slotand the core receiving slot. Optionally, the crowncan comprise only one single face channel. In further aspects, the crowncan comprise a plurality of face channels. Each peripheral slot can be configured to receive fluid moving in a distal direction toward the cutting face of the crown. The face channels can be configured to deliver the fluid from the respective peripheral slot to the core receiving slot. In this way, cuttingsand core segmentscan be flushed through the conduits, into the shank, and through the drill string. The cuttingscan be understood to be the portions of the formation that are formed by engagement between the cutting faceof the crownand the formation, as are formed during conventional drilling.

Optionally, each peripheral slotcan be in fluid communication with a respective face channelthat extends between the peripheral slot and the core receiving slot. In further aspects, at least one peripheral slot(optionally, a plurality of peripheral slots) is not in communication with any of the face channels. In this way, fluid can be delivered to the cutting facefor cooling of the cutting face and removal of cuttings therefrom.

In some optional aspects, the crowncan comprise a plurality of peripheral slotsand at least two face channels. For example, the crowncan comprise at least three peripheral slotsand at least two face channels. Optionally, the crowncan comprise four peripheral slots. In further aspects, the plurality of peripheral slots can consist of four peripheral slots. For example, the crowncan have a first peripheral slot, a second peripheral slot, a third peripheral slot, and a fourth peripheral slot. The first and second peripheral slotscan define a first pair of peripheral slots that are spaced along a first transverse axisthat is perpendicular to (or substantially perpendicular to) the central axis, and the third and fourth peripheral slotscan define a second pair of peripheral slots that are spaced along a second transverse axisthat is perpendicular to (or substantially perpendicular to) the central axis(and, optionally, the first transverse axis).

Referring to, the crowncan comprise a wallthat defines the outer operative circumference of the crown. Optionally, the wallcan be continuous along the entire operative circumference of the crown. The crowncan further comprise a plurality of inner crown portions that define the core receiving slot. For example, the crowncan comprise opposing first and second core-forming inner crown portionsthat define the inner operative circumference and first and second non-core-forming inner crown portions. Optionally, each peripheral slotcan be at least partly defined by a respective inner crown portion. For example, the first peripheral slotcan be defined at least partially by a first outer wall portionof the walland the first non-core-forming inner crown portion, and the second peripheral slotcan be defined at least partially by a second outer wall portionof the walland the second non-core-forming inner crown portion. In further aspects, the third peripheral slotcan be defined at least partially by a third outer wall portionof the walland the first core-forming inner crown portion, and the fourth peripheral slotcan be defined at least partially by a fourth outer wall portionof the walland the second core-forming inner crown portion. In some aspects, the base portion can extend between the first and second core-forming inner crown portions. Optionally, in some aspects, the apexof the base portion can be positioned proximate one of the first or second inner core-forming inner crown portions

In some aspects, each face channelcan be defined, in part or in its entirety, by a respective inner crown portion (e.g., a crown portion selected from among the first and second core-forming inner crown portionsand the first and second non-core-forming inner crown portions). In some optional aspects, the crown portion that at least partially defines a peripheral slot can also define a face channel that extends between said peripheral channel and the core-receiving slot. For example, the first non-core-forming inner crown portioncan define a first face channel. The first face channelcan extend between and be in communication with the core-receiving slotand the first peripheral slot. The second core-forming inner crown portioncan at least partially define a second face channelthat extends between, and is in communication with, the core-receiving slotand the fourth peripheral slot. Referring to, in further aspects, the second non-core forming inner crown portioncan define a third face channelthat extends between the core receiving slotand the second peripheral slot. In optional aspects, one or more of the face channelscan be positioned proximate to one end of the respective peripheral slot. For example, each of the face channelscan be positioned proximate to the clockwise end of each respective peripheral slotwhen viewing the distal end of the drill bit. In this way, the first and second face channelscan deliver fluid to the core-receiving slotproximate to the conduiton the low (proximal-most) side of the breaking surface, which the core segmentsare most likely to break toward and travel through (as illustrated in).

It is contemplated that the peripheral slotscan be sized and positioned in order to provide even or substantially even cutting area (to the extent possible) at different radii from the central axis across the face of the drill bit. In this way, the drill bitcan be configured to wear evenly. The peripheral slotscan further be sized to maximize open area while maintaining the integrity of the bit body. In some aspects, the peripheral slotscan be maintained at a spacing (e.g., radial spacing) of at least 0.3 inches or at least 0.35 inches from each of the core receiving slotand the axial channels. Accordingly, in various aspects peripheral slotson opposing sides of the central axiscan be unevenly spaced from the central axis and can have different arc lengths, radial thickness, and/or cross sectional areas in transverse planes perpendicular to the central axis. As should be understood, the arc length of the peripheral slot can be defined as a length of an arc spaced equally between a radially inner edge of the peripheral slot at the cutting face and a radially outer edge of the peripheral slot at the cutting face. In various exemplary, optional aspects, the first peripheral slotcan have a radius of curvature of between 1 and 2 inches (e.g., about 1.50 inches), an arc length of between 1 and 3 inches (e.g., about 2.34 inches), and an axial width from 0.1 inches to 0.5 inches (e.g., about 0.25 inches); the second peripheral slotcan have a radius of curvature of between 1 and 2 inches (e.g., about 1.39 inches), an arc length of between 1 and 3 inches (e.g., about 1.95 inches), and an axial width from 0.1 inches to 0.5 inches (e.g., about 0.37 inches); the third peripheral slotcan have a radius of curvature of between 1 and 2 inches (e.g., about 1.04 inches), an arc length of between 1 and 3 inches (e.g., about 1.10 inches), and an axial width from 0.1 inches to 0.5 inches (e.g., about 0.29 inches); the fourth peripheral slot can have a radius of curvature of between 1 and 2 inches (e.g., about 1.13 inches), an arc length of between 1 and 2 inches (e.g., about 1.36 inches, and an axial width from 0.1 inches to 0.5 inches (e.g., about 0.29 inches).

Thus, according to some aspects, the at least one peripheral slotcan have a different arc length than at least one other peripheral slot. For example, the first slotcan have a greater arc length than the second slot. In some aspects, the third slotcan have a shorter arc length than the fourth arc length

In further aspects, at least one peripheral slotcan have a radial thickness that is different from another peripheral slot, wherein the radial thickness is defined as the dimension of the slot along an axis that extends radially from the central axis and through the peripheral slot. For example, the first peripheral slotcan have a narrower radial thickness along the first transverse axisthan the second peripheral slot. In further aspects, the third peripheral slotcan have a radial thickness that is less than the fourth peripheral slot. In further aspects, at least two, or, optionally, all of the peripheral slots can have the same radial thickness.

Referring to, in some optional aspects, the first and second core-forming inner crown portionscan each comprise a first axial edge, a second axial edge, and a medial axial edgedisposed between the first axial edgeand the second axial edge. A first inner surfacecan extend between the first axial edgeand the medial axial edge, and a second inner surfacecan extend between the second axial edgeand the medial axial edge. In some aspects, the first inner surfaceof the first core-forming inner crown portioncan be planar or substantially planar. In further aspects, the first inner surfaceof the second core-forming inner crown portioncan be planar or substantially planar. In some optional aspects, the second inner surfaceof the first core-forming inner crown portioncan have a convex curvature. In further optional aspects, the second inner surfaceof the second core-forming inner crown portioncan have a convex curvature. In various other aspects, any of the first or second inner surfaces,of the first and second core-forming inner crown portionscan be planar, concave, or convex, serpentine, or the like, as desirable. For example, in some aspects, each of the first and second inner surfaces,can be planar. In further aspects, each of the first and second inner surfaces,can be concave. In still further aspects, the first and second surfaces,of the first and second core-forming inner crown portionscan be defined by a single continuous surface profile with no definite boundary therebetween.

In some embodiments, the innermost surfaces of the crowncan be longitudinal medial edgesof the first and second core-forming inner crown portions. As the drill bitrotates, the innermost surfaces can circumscribe, and thereby define, the core receiving space. In some aspects, the core receiving space can be cylindrical. Thus, in use, the core received within the core receiving slotcan form a cylindrical core sample portion.

In some aspects, a first planecan contain the first axial edgeand the medial axial edgeof the first core-forming inner crown portion, and a second planecan contain the second axial edgeand the medial axial edgeof the first core-forming inner crown portion. In some aspects, the first and second planes,can be angularly oriented relative to one another at an angle, β1, of greater than 180 degrees, such as, for example, an angle from about 190 degrees to about 240 degrees. In some aspects, a third planecan contain the first axial edgeand the medial axial edgeof the second core-forming inner crown portion, and a fourth planecan contain the second axial edgeand the medial axial edgeof the second core-forming inner crown portion. In some aspects, the third and fourth planes,be angularly oriented relative to one another at an angle, β2, of greater than 180 degrees, such as, for example, an angle from about 190 degrees to about 240 degrees. For example, optionally, each of β1 and β2 can be at least about 180 degrees, between about 190 and 260 degrees, or about 245 degrees. It is contemplated that a greater angle can increase penetration rate by increasing the open area of the bit while decreasing bit life by removing material from the bit that is subject to the greatest amount of wear.

As one will appreciate, during normal clockwise rotation of the drill bit, the second inner surfaceof the first and second core-forming inner crown portionscan serve as the leading edges of the drill bit. However, it is contemplated that the direction of rotation of the drill bit can be reversed so that the first inner surfacesof the first and second core-forming inner crown portionscan serve as the leading edges of the drill bit.

In some aspects, the first and second non-core-forming inner crown portionscan have respective inner surfacesthat have concave curvatures.

Although various edges, planes, surfaces, and angles disclosed in the preceding paragraphs are only depicted in(with respect to an embodiment including three face channels), it is contemplated that these same edges, planes, surfaces, and angles (and other associated features) can be present in other embodiments disclosed herein, including embodiments with only two face channels.

Referring to, in some optional aspects, distal of the apex() of the base portion, the first and second inner surfaces of the first crown portion can be rotationally symmetric to the first and second inner surfaces of the second crown portion about the central axis. That is, it is contemplated that after some amount of rotation (optionally, about 180 degrees of rotation) of the second crown portion, the first and second inner surfaces of the second crown portion can look the same or substantially the same as the first and second inner surfaces of the first crown portion. Accordingly, in some aspects, distal of the apexof the base portion, the core receiving slotcan have at least two degrees of rotational symmetry about the central axisof the drill bit.

In some aspects, the medial axial edgesof the first and second core forming inner crown portionsare positioned on opposite sides of the first transverse axis.

The wallcan define at least one axial channelthat is radially inwardly recessed from the outer operative circumferenceof the crown. For example, the wall can define a plurality of (e.g., three) axial channels on each side of the bit that are spaced along the second transverse axis. The axial channelscan permit fluid flowing from the peripheral channelsand across the cutting face to return distally along the outer surface of the drill string.

In some optional aspects, the crowncan be impregnated with diamonds, thereby allowing the crown to be used to cut hard formations and/or to increase the durability of the bit. The part of the bit that performs the cutting action, sometimes referred to as a face, can be generally formed of a matrix that contains a powdered metal or a hard particulate material, such as tungsten carbide. This material can be infiltrated with a binder, such as a copper-based alloy. The matrix and binder associated with the face can be mixed (impregnated) with diamond crystals (synthetic or natural) or another form of abrasive cutting media using conventional methods. As the drill bit grinds and cuts through the formation, the matrix and binder can erode and expose new layers of the diamond crystal (or other cutting media) so that sufficient cutting action is maintained during use of the drill bits disclosed herein.

In exemplary aspects, the crowncan optionally comprise a plurality of projectionsextending distally from the cutting face. Optionally, the projectionscan be integrally formed with the crown. Accordingly, the projectionscan comprise the same matrix as the crown. In further embodiments, the projectionscan comprise matrices that are different from their respective crowns. U.S. Pat. No. 9,637,980, issued to Longyear TM Inc. on Aug. 15, 2017, which is hereby incorporated herein by reference in its entirety, discloses further aspects of diamond impregnated bits and associated projections that can optionally be implemented with the drill bit. Optionally, in some aspects, the projectionscan be distributed among a plurality of arcuate rows, with each arcuate row containing projections having a center point that is located at a given radius from the central axis. Optionally, in these aspects, it is contemplated that the projections within at least one arcuate row can radially overlap or be radially staggered with the projections of at least one other arcuate row. In further aspects, it is contemplated that the plurality of projectionscan be evenly or substantially evenly distributed throughout the cutting face. In other aspects, it is contemplated that the plurality of projectionscan have an uneven distribution, with selected areas of the cutting facehaving a greater concentration of projections than other areas of the cutting face.

In various optional aspects, the peripheral slots cooperatively define a total open area (in cross sections in planes transverse to the longitudinal axis) that is at least the cross sectional area defined by the inner surface of the inner tube, further described herein, used with the drill bit. For example, in some aspects, the total open area of the peripheral slots can be at least 90%, at least 100%, at least 110%, at least 120%, or about 116% of the inner area of the inner tube. In this way, the bit can permit sufficient flow to return through the inner tube. According to some optional aspects, the total open area of the bit, determined by subtracting the surface area of the cutting face from the total area within the outer operative circumference, is between about 30% and about 50% (e.g., about 40%) of the total area within the operative circumference. For example, the total open area of the bit can be about 36%. Optionally, the core receiving slot can define between about 5% and about 15% (e.g., about 10%) of the area within the inner circumference of the drill bit. Optionally, the peripheral slotscan cooperatively define an area in a plane transverse to the longitudinal axis of the bit that is between about 15% and about 20% (e.g., about 17%) of the area within the inner circumference of the drill bit. Optionally, the axial channelscan cooperatively define an area in a plane transverse to the longitudinal axis of the bit that is between 0 and about 5% (e.g., about 3%) of the area within the inner circumference of the drill bit. Optionally, the face channelscan cooperatively define an area in a plane transverse to the longitudinal axis of the bit that is between about 5% and about 10% (e.g., about 6%) of the area within the inner circumference of the drill bit.

Referring to, a drilling assemblycan comprise an outer tubeand an inner tubereceived within the inner tube. The inner tubeand outer tubecan cooperate to define an annular space. A drill bit (e.g., the drill bit) can be coupled to the outer tube. For example, the shankcan be threadedly coupled to the outer tube.