Fixed cutter drill bit with co-orbital primary and backup cutters
阅读说明:本技术 具有同轨设置的初级切削齿和备用切削齿的固定切削齿钻头 (Fixed cutter drill bit with co-orbital primary and backup cutters ) 是由 陈世林 于 2018-07-13 设计创作,主要内容包括:本公开涉及具有同轨设置的初级切削齿和备用切削齿的固定切削齿钻头、设计这种钻头的方法、实现这种方法的系统以及使用这种固定切削齿钻头在地质地层中钻取井眼的系统。(The present disclosure relates to fixed cutter drill bits having primary and backup cutters in co-orbital arrangement, methods of designing such drill bits, systems for performing such methods, and systems for drilling wellbores in geological formations using such fixed cutter drill bits.)
1. A fixed-cutter drill bit, comprising:
a bit body including at least two blades and having a bit rotational axis about which the drill bit rotates in a direction during use;
a primary cutting tooth positioned on a first blade and having a profile angle, wherein the primary cutting tooth is a primary cutting tooth when the drill bit is initially in use; and
a backup cutter co-orbital with the primary cutter and having less than delta exposure along the profile angle of the primary cutter, the backup cutter positioned on a second blade at an angle θ measured from the primary cutter in a direction opposite the direction the drill bit rotates during use relative to the bit rotational axis of the drill bit, wherein θ is greater than or equal to 150 degrees.
2. The fixed-cutter drill bit of claim 1, wherein the position of the backup cutter on the drill bit is determined by:
selecting a primary cutting tooth on the first blade;
determining the profile angle of the primary cutting tooth;
selecting a selected target critical depth of cut (CDOC) for the backup cutterb);
Selecting a wear w of the primary cutter that, when reached, the backup cutter will engage the formation during use of the drill bit;
selecting a second blade for the backup cutter such that an angle θ based on the selection is greater than or equal to 150 degrees;
selecting the under-exposure δ of the backup cutting tooth along the profile angle of the primary cutting tooth.
3. The fixed-cutter drill bit of claim 2, wherein the position of the backup cutter on the drill bit is further determined by:
calculating an actual CDOC for the backup cutting tooth using one of the following equationsb:
CDOCb((δ -w) x360)/θ or CDOCb(w x360)/θ; and
integrating the actual CDOCbWith the selected target CDOCbMaking a comparison and if the actual CDOCbIs not greater than or equal to the selected target CDOCbRepeating the step of selecting the underexposure δ and continuing the subsequent steps with a different underexposure δ, or
If the actual CDOCbIs greater thanOr equal to the target CDOCbComparing the selected underexposure δ with the selected wear w and if the selected underexposure δ is not greater than or equal to the selected wear w, repeating the step of selecting a second blade and continuing the subsequent steps with a different second blade, or
Positioning the backup cutting tooth on the second blade at the angle θ and the under-exposure δ if the selected under-exposure δ is greater than or equal to the selected wear w.
4. The fixed-cutter drill bit of claim 1, wherein the angle θ is between 150 and 210 degrees, and the backup cutter becomes a primary cutter during use of the drill bit, and the primary cutter remains a primary cutter when the backup cutter is also a primary cutter.
5. The fixed cutter drill bit of claim 1, wherein the angle θ is 180 degrees or greater.
6. The fixed-cutter drill bit of claim 1, wherein the angle θ is between 210 and 330 degrees, the backup cutter becomes a primary cutter during use of the drill bit, and the primary cutter becomes a secondary cutter when the backup cutter is a primary cutter.
7. A system for drilling a wellbore in a formation, the system comprising:
a drill string;
a fixed-cutter drill bit attached to the drill string, the fixed-cutter drill bit comprising:
a bit body including at least two blades and having a bit rotational axis about which the drill bit rotates in a direction during use;
a primary cutting tooth positioned on a first blade and having a profile angle, wherein the primary cutting tooth is a primary cutting tooth when the drill bit is initially in use; and
a backup cutter co-orbital with the primary cutter and having less than delta exposure along the profile angle of the primary cutter, the backup cutter positioned on a second blade at an angle θ measured from the primary cutter in a direction opposite the direction the drill bit rotates during use relative to the bit rotational axis of the drill bit, wherein θ is greater than or equal to 150 degrees.
8. The system of claim 7, wherein the position of the backup cutter on the drill bit is determined by:
selecting a primary cutting tooth on the first blade;
determining the profile angle of the primary cutting tooth;
selecting a selected target critical depth of cut (CDOC) for the backup cutterb);
Selecting a wear w of the primary cutter that, when reached, the backup cutter will engage the formation during use of the drill bit;
selecting a second blade for the backup cutter such that an angle θ based on the selection is greater than or equal to 150 degrees;
selecting the under-exposure δ of the backup cutting tooth along the profile angle of the primary cutting tooth.
9. The system of claim 7, wherein the position of the backup cutter on the drill bit is further determined by:
calculating an actual CDOC for the backup cutting tooth using one of the following equationsb:
CDOCb((δ -w) x360)/θ or CDOCb(w x360)/θ; and
integrating the actual CDOCbWith the selected target CDOCbMaking a comparison and if the actual CDOCbNot more than or equal to theSelected target CDOCbRepeating the step of selecting the underexposure δ and continuing the subsequent steps with a different underexposure δ, or
If the actual CDOCbGreater than or equal to the target CDOCbComparing the selected underexposure δ with the selected wear w and if the selected underexposure δ is not greater than or equal to the selected wear w, repeating the step of selecting a second blade and continuing the subsequent steps with a different second blade, or
Positioning the backup cutting tooth on the second blade at the angle θ and the under-exposure δ if the selected under-exposure δ is greater than or equal to the selected wear w; and
a surface assembly that rotates the drill string and the drill bit during drilling of a wellbore in a formation using the drill bit.
10. The system of claim 1, wherein the angle θ is 180 degrees or greater.
11. A method, comprising:
providing an incomplete bit design comprising:
a bit body including at least two blades and having a bit rotational axis about which the drill bit rotates in a direction during use;
a primary cutting tooth positioned on a first blade and having a profile angle, wherein the primary cutting tooth is a primary cutting tooth when the drill bit is initially in use; and
determining a position of a backup cutter, the backup cutter being co-orbital with the primary cutter and having less than δ exposure along the profile angle of the primary cutter, the backup cutter being positioned on a second blade at an angle θ measured from the primary cutter relative to the bit rotational axis of the drill bit in a direction opposite to a direction in which the drill bit rotates during use, wherein θ is greater than or equal to 150 degrees, wherein determining the position of the backup cutter comprises:
selecting a primary cutting tooth on the first blade;
determining the profile angle of the primary cutting tooth;
selecting a selected target critical depth of cut (CDOC) for the backup cutterb);
Selecting a wear w of the primary cutter that, when reached, the backup cutter will engage the formation during use of the drill bit;
selecting a second blade for the backup cutter such that an angle θ based on the selection is greater than or equal to 150 degrees;
selecting the under-exposure δ of the backup cutting tooth along the profile angle of the primary cutting tooth;
calculating an actual CDOC for the backup cutting tooth using one of the following equationsb:
CDOCb((δ -w) x360)/θ or CDOCb(w x360)/θ; and
integrating the actual CDOCbWith the selected target CDOCbMaking a comparison and if the actual CDOCbIs not greater than or equal to the selected target CDOCbRepeating the step of selecting the underexposure δ and continuing the subsequent steps with a different underexposure δ, or
If the actual CDOCbGreater than or equal to the target CDOCbComparing the selected underexposure δ with the selected wear w and if the selected underexposure δ is not greater than or equal to the selected wear w, repeating the step of selecting a second blade and continuing the subsequent steps with a different second blade, or
Positioning the backup cutting tooth on the second blade at the angle θ and the under-exposure δ if the selected under-exposure δ is greater than or equal to the selected wear w.
12. The method of claim 11, wherein the angle θ is between 150 and 210 degrees, and the backup cutter becomes a primary cutter during use of the drill bit, and the primary cutter remains a primary cutter when the backup cutter is also a primary cutter.
13. The method of claim 11, wherein the angle θ is 180 degrees or greater.
14. The method of claim 11, wherein the angle θ is between 210 and 330 degrees, the backup cutter becomes a primary cutter during use of the drill bit, and the primary cutter becomes a secondary cutter when the backup cutter is a primary cutter.
15. The method of claim 11, further comprising manufacturing a drill bit according to the incomplete drill bit design, wherein the backup cutter is positioned on the second blade at the angle θ and the exposure deficit δ.
Technical Field
The present disclosure relates generally to fixed cutter drill bits having primary and backup cutters arranged in-track, methods of designing such drill bits, systems for performing such methods, and systems for drilling wellbores in geological formations using such fixed cutter drill bits.
Background
Wellbores are most often formed in geological formations using earth-boring drill bits. There are various types of such drill bits, but they all experience some type of wear or fatigue from use, which limits the overall life of the drill bit or the time used downhole in the wellbore before returning to the surface. The materials used in drill bits and their ability to effectively cut the different types of formations encountered as the wellbore advances sometimes also necessitate that the drill bit be removed from the wellbore, replaced or a component of the drill bit, and then returned downhole to restore the cut.
In particular, as the wellbore reaches greater lengths, the process of retrieving and returning the drill bit becomes time consuming and expensive. In addition, the drill bit and bit components themselves are expensive and time consuming to manufacture or replace. Accordingly, those involved in designing, manufacturing, and operating earth-boring drill bits and their components spend a great deal of time developing methods to limit the removal and return of the drill bit in the wellbore and to increase the life of the drill bit and its components. However, these attempts have been complicated by the fact that earth-boring drill bits and their components and operations tend to be very complex, resulting in some improvements being found impractical.
Drawings
A more complete understanding of the features of the present disclosure and the advantages thereof may be acquired by referring to the following description in consideration with the accompanying drawings, in which like reference numbers indicate like features, and wherein:
FIG. 1 is a schematic illustration of a drilling system in which a fixed cutter drill bit having primary and backup cutters in an in-orbit arrangement according to the present disclosure may be used;
FIG. 2 is an isometric view of a fixed cutter drill bit having primary and backup cutters in an in-orbit arrangement;
FIG. 3 is a schematic diagram showing the relative positions of a primary cutter and an in-orbit spare cutter;
FIG. 4 is a graph of depth of cut for the primary cutter and backup cutter of FIG. 3 as a function of angle (θ);
FIG. 5 (left) is a schematic illustration of the relative positions of primary cutters and coaxially disposed backup cutters on a fixed cutter drill bit; FIG. 5 (right) is a trajectory diagram of a cutter of a fixed cutter drill bit;
FIG. 6 is a set of schematic views of the area of engagement of a primary cutter and an in-orbit positioned backup cutter as a function of angle θ;
FIG. 7 (left) is a schematic illustration of the underexposure (δ) of the primary cutting tooth when there is no wear on the primary cutting tooth, and the backup cutting tooth disposed in-orbit; FIG. 7 (right) is a schematic illustration of relative underexposure of a primary cutting tooth, and a backup cutting tooth disposed in-track when there is wear (w) on the primary cutting tooth;
FIG. 8 is a graph of calculated bit wear for a fixed cutter drill bit;
FIG. 9 is a graph of the change in cutting edge during wear of the cutting teeth of a fixed cutter drill bit, with the broken line indicating the worn cutting edge;
FIG. 10 is a schematic illustration of primary cutters on a fixed cutter drill bit prior to a method of designing for placement of a backup cutter in an in-orbit configuration;
FIG. 11 is a critical depth of cut (CDOC) for a backup cutter as a function of primary cutter wear (w) and drilling distanceb) A graph of (a);
FIG. 12 is a flow chart of a method for designing a fixed cutter drill bit having primary cutters and backup cutters in an in-orbit arrangement.
FIG. 13 is a schematic view of a fixed cutter drill bit having primary cutters and backup cutters in an in-orbit arrangement;
FIG. 14 is a critical depth of cut (CDOC) for a backup cutter as a function of bit radius for the fixed cutter drill bit of FIG. 13b) A graph of (a);
FIG. 15 is a graphical representation of the drilling distances achieved with the fixed cutter drill bit of FIG. 13 (labeled "New drill bit") as compared to other fixed cutter drill bits not designed according to the present disclosure;
FIG. 16 is a photograph of the drill bit of FIG. 13 after use in a passive state;
FIG. 17 is a graph of the rate of penetration (ROP) using a fixed cutter drill bit having six blades and having primary cutters and orbitally disposed backup cutters, wherein the orbitally disposed backup cutters are positioned on different blades;
FIG. 18 is a graph of drilling distance using a fixed cutter drill bit having six blades and having primary cutters and orbitally disposed backup cutters, wherein the orbitally disposed backup cutters are positioned on different blades;
FIG. 19 is a graph of ROP using a fixed cutter drill bit having six blades and having a primary cutter and an in-orbit backup cutter, wherein the in-orbit backup cutter is positioned rotationally four blades behind the primary cutter and has a chamfer that is less than the chamfer of the primary cutter;
FIG. 20 is a graph of drilling distance using a fixed cutter drill bit having six blades and having a primary cutter and an in-orbit backup cutter, wherein the in-orbit backup cutter is positioned rotationally four blades behind the primary cutter and has a chamfer that is less than the chamfer of the primary cutter;
FIG. 21 is a graph of ROP using a fixed cutter drill bit having six blades and having a primary cutter and an in-orbit backup cutter, wherein the in-orbit backup cutter is positioned rotationally four blades behind the primary cutter and has a backrake angle that is less than the backrake angle of the primary cutter;
fig. 22 is a graph of drilling distance using a fixed cutter drill bit having six blades and having a primary cutter and an in-orbit backup cutter, wherein the in-orbit backup cutter is positioned rotationally four blades behind the primary cutter and has a backrake angle that is less than the backrake angle of the primary cutter.
Detailed Description
The present disclosure relates to fixed cutter drill bits having primary cutters and backup cutters disposed in-track. In particular, the present disclosure relates to methods of designing such drill bits to determine the appropriate position of the backup cutters disposed in-orbit. The present disclosure also relates to systems for implementing the drill bit design methods, fixed cutter drill bits designed using such methods, and systems for forming wellbores in geological formations using such drill bits.
The methods of the present disclosure may be used to design drill bits that extend the life of the drill bit without sacrificing penetration speed. The method may also be used to design a drill bit that can be used to drill both soft and hard formations without removing the drill bit from the wellbore, replacing the drill bit with a different drill bit, or replacing the cutters with different cutters, and then returning the drill bit to the wellbore.
The present disclosure may be further understood with reference to fig. 1-22, wherein like numerals are used to indicate like and corresponding parts.
FIG. 1 is a schematic illustration of a
The wellbore 114 may be defined in part by a casing string 110, which may be extended from the well site 106 to a selected downhole location. As shown in fig. 1, the portion of the wellbore 114 that does not include the casing string 110 may be described as "open hole". Various types of drilling fluids may be pumped from well site 106 through drill string 103 to attached
FIG. 2 is an isometric view of fixed-
The plurality of blades 126 (e.g.,
In some cases, one or
In some cases,
The
One or more of the cutting
Typically, a wellbore, such as wellbore 114, will be drilled through formations having different properties (such as different hardnesses). Instead of using two different drill bits to drill the two formations, a fixed
When designing a fixed
During drilling, fixed
For a given footage rate in feet per hour and revolutions per minute, the depth of cut in inches per revolution of fixed
DOC=ROP/(5xRPM) (1a)。
the DOC in equation (1a) is defined at the bit level. However, the DOC may be shared by the
During one rotation of fixed
The depth of cut (DOC) in inches/revolution of point Pb may be calculated as a function of angle θ, which is the angle between point Pa and point Pb measured relative to bit rotational axis 104:
DOCb=DOCθ/360 (1b)。
the depth of cut of point Pa may be calculated in inches per revolution as:
DOCa=DOC-DOCb(1c.)
in an example method of designing a fixed
As shown in fig. 4, when backup cutter 128B trails primary cutter 128A by an angle θ of 180.0 degrees, primary cutter 128A and backup cutter 128B share equally the depth of cut (DOC) of fixed-
When the backup cutter 128B rotationally trails the primary cutter 128A by an angle θ less than 180.0 degrees, the primary cutter 128A shares a greater depth of cut (DOC) than the backup cutter 128B because the primary cutter 128A engages the formation deeper than the backup cutter 128B. In this case, the primary cutting tooth 128A is a primary cutting tooth and the backup cutting tooth 128B is a secondary cutting tooth.
When the backup cutter 128B rotationally trails the primary cutter 128A by an angle θ greater than 180.0 degrees, the backup cutter 128B shares a greater depth of cut (DOC) than the primary cutter 128A because the backup cutter 128B engages the formation deeper than the primary cutter 128A. In this case, the backup cutter 128B is a primary cutter, and the primary cutter 128A is a secondary cutter.
Applying the principles of this example more generally, for a pair of co-orbital cutters, which cutter is the primary cutter and which cutter is the secondary cutter depends on the angular position of the cutter as measured relative to the bit rotational axis of the fixed cutter drill bit in which the cutter is located.
In another example of a method of designing a fixed
Using the variation of fixed
Specifically, in fig. 6A, backup cutter 128B rotationally trails primary cutter 128A (backup cutter 128B on blade 1) at an angle θ of 23.69 degrees. The primary cutting tooth 128A has an engagement area 8.8 times that of the backup cutting tooth 128B, such that the primary cutting tooth 128A is a primary cutting tooth and the backup cutting tooth 128B is a secondary cutting tooth. The cutting efficiency of the backup cutter 128B is very low due to the depth of cut (DOC) of the cutter Bb) Too low to form any rock chips in front of the backup cutter 128B.
In fig. 6B, backup cutter 128B rotationally trails primary cutter 128A (backup cutter 128B on blade 6) by an angle θ of 83.38 degrees. The engagement area of the primary cutting tooth 128A is still larger than the engagement area of the backup cutting tooth 128B so that the primary cutting tooth 128A is still the primary cutting tooth and the backup cutting tooth 128B is the secondary cutting tooth, but the engagement area of the backup cutting tooth 128B is increased compared to when the backup cutting tooth 128B is on the
In fig. 6C, backup cutter 128B rotationally trails primary cutter 128A (backup cutter 128B on blade 5) at an angle θ of 148.72 degrees. The primary cutting tooth 128A has an engagement area of 0.03036in2And the engaging area of the backup cutting teeth 128B is 0.024916in2. Although the two cutting teeth have nearly the same area of engagement, the primary cutting tooth 128A remains the primary cutting tooth and the backup cutting tooth 128B remains the secondary cutting tooth.
In fig. 6D, backup cutter 128B rotationally trails primary cutter 128A (backup cutter 128B on blade 4) at an angle θ of 197.29 degrees. The primary cutting tooth 128A has an engagement area of 0.02475in2And the engaging area of the backup cutting teeth 128B is 0.03314in2. Although both cutting teeth also have nearly the same area of engagement, the backup cutting tooth 128B is the primary cutting tooth in this configuration, while the primary cutting tooth 128A is the secondary cutting tooth.
In fig. 6E, backup cutter 128B rotationally trails primary cutter 128A at an angle θ of 257.12 degrees (backup cutter 128B on blade 3). The primary cutting tooth 128A has an engagement area of 0.01648in2And the engaging area of the backup cutting teeth 128B is 0.025514in2. The backup cutter 128B has a larger engagement area than the primary cutter 128A such that the backup cutter 128B is the primary cutter and the primary cutter 128A is the secondary cutter.
In fig. 6F, backup cutter 128B rotationally trails primary cutter 128A at an angle θ of 319.97 degrees (backup cutter 128B on blade 3). The primary cutting tooth 128A has an engagement area of 0.00621in2And the engaging area of the backup cutting teeth 128B is 0.035785in2. The backup cutter 128B has a significantly larger engagement area than the primary cutter 128A such that the backup cutter 128B is the primary cutter and the primary cutter 128A is the secondary cutter.
The above examples illustrate how the angle θ between the cutters (even when the two cutters are in-orbit) plays an important role in their relative engagement area with the formation. The principles of this example may be applied to the design of fixed cutter drill bits.
In particular, in order for backup cutter 128B to have a smaller engagement area than primary cutter 128A, backup cutter 128B may be positioned rotationally behind cutter a by an angle θ of less than 180 degrees. In fixed
In order for backup cutter 128B and primary cutter 128A to have similar engagement areas, backup cutter 128B may be positioned rotationally behind primary cutter 128A at an angle θ of 180 degrees or close to 180 degrees. In fixed
In order for backup cutter 128B to have a larger engagement area than primary cutter 128A, backup cutter 128B may be positioned rotationally trailing primary cutter 128A at an angle θ of greater than 180 degrees, typically 210 to 330 degrees. In fixed
In order for backup cutter 128B to be the primary cutter, the backup cutter should be positioned rotationally behind primary cutter 128A by an angle θ of 180 degrees or more.
The above example of the effect of angle θ on the area of engagement of primary cutter 128A and backup cutter 128B assumes that the two cutters on fixed
Due to the underexposure, backup cutter 128B may or may not engage the formation for a given depth of cut (DOC) of fixed
CDOCb=(δx360)/θ (2a)。
if the fixed
For some fixed cutter bits, CDOCbMay be constant. Thus, the underexposure δ in inches may be a linear function of θ, as described by the following equation:
δ=(CDOCbxθ)/360 (2b)。
thus, for a given CDOCbDepending on the angle θ between primary cutter 128A and backup cutter 128B, fixed cutter drill bits having various distances δ that are underexposed may be designed.
In such a bit, if the primary cutter 128A never experienced any wear, the primary cutter 128A will always remain the primary cutter, while the backup cutter 128B will always remain the secondary cutter. However, in general, the purpose of including backup cutting teeth is to share cutting duties when the primary cutting teeth experience wear. Accordingly, methods of designing fixed cutter drill bits typically take into account cutter wear in addition to cutter placement.
Any of a variety of methods of modeling cutting tooth wear may be used in conjunction with the present disclosure. For example, in a model of Polycrystalline Diamond Compact (PDC) cutters based on single cutter testing, cutter wear is proportional to cutter load, cutting speed, and temperature. Such models may further be incorporated into a bit level model that further takes into account the location of the cutter on a fixed cutter bit. Typically, the cutting tooth wear model used in connection with the present disclosure has been validated through laboratory testing.
For example, a model may be used to determine cutting tooth wear. Other models that take into account the location of the cutter on a fixed cutter drill bit may be used to determine cutter wear. An example graph of cutter wear along a bit profile of a fixed cutter drill bit calculated using a cutter wear model is provided in fig. 8. The average bit blunting in this bit profile is 2 out of 8. An example graph of the change in cutting edge during cutter wear on a fixed cutter drill bit calculated using a cutter wear model is provided in fig. 9. Both sharp and worn cutting edges are depicted.
CDOCbAs a function of the wear w of the primary cutting tooth 128A. This effect can be considered in a modified equation similar to equation 2a above:
CDOCb=((δ-w)x360)/θ (2c)。
the right hand drawing in fig. 7 also shows the wear w of the primary cutting tooth 128A. When the wear w of the primary cutting tooth 128A is equal to the under-exposure δ of the backup cutting tooth 128B, then CDOCbIs zero and the backup cutting tooth 128B functions as an active cutting tooth. Thus, fixed
Due to the overlap of adjacent cutting teeth, CDOCbMay be more complex than equation 2 c. The CDOC may be calculated using various models, typically implemented by a computerb. In particular, a cutting tooth wear model may be used to derive drilling informationA prediction of cutting element wear is made.
Typically, fixed
In another example of a fixed
If the backup cutting tooth 128B is positioned on the
If the backup cutter 128B is positioned on
If the backup cutter 128B is positioned behind both blades of the primary cutter on
If the backup cutter 128B is positioned on
If the backup cutter 128B is positioned on
If the backup cutter 128B is positioned on
The optimal placement of the backup cutter 128B may be further evaluated. FIG. 11 is a graph of critical depth of cut as a function of cutting tooth wear and drilling distance and can be used for this further evaluation.
If the backup cutter 128B is positioned three blades behind the primary cutter, then the CDOCbThe CDOC in FIG. 11 will be followedb
If the backup cutter 128B is positioned four blades behind the primary cutter, then the CDOCbThe CDOC in FIG. 11 will be followedb
The principles described herein may be applied to
Fixed
Fixed
The under-exposure delta can be zero, in which case theta can be greater than or equal to 180 degrees or 240 degrees.
Other parameters of fixed
For example, backup cutter 128B may have a chamfer between cutting
Further, the chamfer length of both primary cutter 128A and backup cutter 128B may be reduced to improve both bit life and ROP. For example, the chamfer length can be 0.010 inches or less, between 0.005 inches and 0.015 inches, between 0.0075 and 0.0125 inches, or between 0.001 inches and 0.010 inches, rather than the more typical 0.020 inches.
Additionally, the backup cutter 128B may have a backrake angle that is less than the backrake angle of the primary cutter 128A. In particular, the back rake angle of the backup cutting tooth 128B may be at least 2 degrees, at least 5 degrees, or at least 10 degrees less than the back rake angle of the primary cutting tooth 128A.
Further, the back rake angle of both primary cutter 128A and backup cutter 128B may be limited to improve both bit life and ROP. For example, a back rake angle of 15 degrees or less, 10 degrees or less, or 5 degrees or less may be used, particularly if impact damage to the cutting tooth is not a concern.
Other design parameters may further improve bit life and ROP. These include the use of a reduced number of blades such as 5 or less or 6 or less blades, smaller cutters, multi-stage force balanced cutter arrangements (particularly pairs of cutters), and opposing cutter arrangements disposed in-track rather than leading or trailing cutter arrangements disposed in-track.
In
In
In
In
In
In
In step 214, the size and position and/or orientation of backup cutter 128B relative to the remainder of fixed
In
In step 218, the actual CDOCbWith the selected target CDOC of step 206bA comparison is made. If the actual CDOC of
In step 218, the selected under exposure δ of
The
For example, in addition to the steps of
Also, in addition to the steps of
The steps of
In general, computer programs and models for simulating and designing drilling systems may be referred to as "drilling engineering tools" or "engineering tools". Since
In embodiment a, the present disclosure provides a fixed-cutter drill bit comprising: a bit body comprising at least two or at least three blades and having a bit rotation axis about which the drill bit rotates in a direction during use; a primary cutting tooth positioned on the first blade and having a profile angle, wherein the primary cutting tooth is a primary cutting tooth when the drill bit is initially in use; and a backup cutter co-orbital with the primary cutter and having less than delta exposure along a profile angle of the primary cutter, the backup cutter positioned on the second blade at an angle θ measured from the primary cutter relative to a bit rotational axis of the drill bit in a direction opposite a direction in which the drill bit rotates during use, wherein θ is greater than or equal to 150 degrees.
In embodiment B, the present disclosure also provides a system for drilling a wellbore in a subterranean formation, wherein the system comprises: a drill string; a fixed cutter drill bit attached to a drill string as described in embodiment a; and rotating the surface assembly of the drill bit and the drill string during drilling of the wellbore in the formation using the drill bit.
In a third embodiment C, the present disclosure provides a method comprising providing an incomplete drill bit design comprising: a bit body comprising at least two or at least three blades and having a bit rotation axis about which the drill bit rotates in a direction during use; a primary cutting tooth positioned on the first blade and having a profile angle, wherein the primary cutting tooth is a primary cutting tooth when the drill bit is initially in use; and determining a position of a backup cutting tooth, the backup cutting tooth being co-orbital with the primary cutting tooth and having less than delta exposure along the profile angle of the primary cutting tooth, the backup cutting tooth being positioned to be co-orbital with the primary cutting tooth and having less than delta exposure along the profile angle of the primary cutting toothThe cutter is positioned on the second blade at an angle θ measured from the primary cutter relative to a bit rotational axis of the drill bit in a direction opposite to a direction in which the drill bit rotates during use, where θ is greater than or equal to 150 degrees. Determining the position of the backup cutting tooth includes: selecting a primary cutting tooth on a first blade; determining a profile angle of the primary cutting tooth; selecting a selected target critical depth of cut (CDOC) for a backup cutterb) (ii) a Selecting a wear w of the primary cutter at which the backup cutter will engage the formation during use of the drill bit; selecting a second blade for the backup cutting tooth such that the angle θ based on the selection is greater than or equal to 150 degrees; selecting an under-exposure δ of the backup cutting tooth along the profile angle of the primary cutting tooth; calculating an actual CDOC for a backup cutter using one of the following equationsb:CDOCb((δ -w) x360)/θ or CDOCb(wx360)/θ; and the actual CDOCbWith the selected target CDOCbMake a comparison and if the actual CDOCbIs not greater than or equal to the selected target CDOCbThe step of selecting the under exposure delta is repeated and the subsequent steps are continued with a different under exposure delta or if the actual CDOC isbGreater than or equal to the target CDOCbThe selected under-exposure δ is compared to the selected wear w and if the selected under-exposure δ is not greater than or equal to the selected wear w, the step of selecting a second blade is repeated and the subsequent steps are continued with a different second blade or if the selected under-exposure δ is greater than or equal to the selected wear w, a backup cutting tooth is positioned on the second blade at the angle θ and the under-exposure δ.
In embodiment D, the present disclosure provides a drilling engineering tool comprising instructions stored on a computer readable medium and operable when executed to perform a method of designing the fixed-cutter drill bit of embodiment C.
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