A Preferred Method and Device for the Structure of Conical PDC Teeth

Abstract

The present invention provides a method for optimizing the structure of a conical PDC tooth, which includes: establishing a contact stiffness calculation model based on formation parameters and the apex parameters of the conical PDC tooth to calculate the contact stiffness; establishing an apex radius calculation model based on formation parameters, construction parameters, bit parameters, and contact stiffness to calculate the apex radius. The present invention has the following beneficial effects: It can provide scientific guidance for the optimization of conical PDC teeth, can select a suitable conical tooth structure in combination with the formation conditions, and can avoid the situation that the conical PDC tooth cannot penetrate in hard formations or penetrates too deep in plastic formations due to inappropriate structure. By optimizing the conical PDC teeth through this method, it is expected to improve the mechanical drilling rate of the bit with conical PDC teeth in extremely hard formations and extend the service life of the bit.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling engineering, and more particularly, to a method and device for optimizing the structure of conical PDC teeth. Background Art

[0002] In recent years, with the acceleration of the process of oil and gas resource development in China, exploration and development have gradually moved towards deep formations (vertical well depth exceeding 4,500 meters). During the process of oil and gas exploration and development, due to the advantages of PDC bits such as no rotating parts, high mechanical drilling speed, and long service life, they have been increasingly widely used and have almost replaced conventional roller cone bits. However, conventional PDC teeth have poor drilling performance in deep and ultra-hard formations. The main reasons are as follows:

[0003] (1) Deep and dense shale has extremely high hardness, and conventional PDC teeth cannot effectively penetrate the formation, resulting in the grinding of PDC teeth on the rock surface and causing premature failure of PDC teeth.

[0004] (2) In addition to extremely high hardness, deep formations exhibit high plasticity under the action of bottom-hole confining pressure, which causes excessive energy consumption of PDC bits during drilling operations in rock plastic work, thus greatly reducing the rock-breaking efficiency.

[0005] In order to further improve the mechanical drilling speed and service life of PDC bits in hard formations, various special-shaped tooth structure bits have emerged one after another, among which conical teeth are more common. The tip of the conical tooth can easily penetrate the rock and form a "plow groove" on the rock surface, thus achieving the purpose of improving the rock-breaking efficiency of hard rock. The tip and the conical surface of the conical tooth are both high-wear-resistant polycrystalline diamond layers, which can ensure the working life of the tooth. The tangential impact resistance and penetration ability of conical PDC teeth are closely related to the working environment and the structure of the conical tooth. When designing the structure of the conical tooth, it needs to be considered key points, but currently it mainly relies on the experience of engineers and lacks a scientific evaluation and optimization method.

[0006] In view of the above problems of the prior art, the present invention provides a method and device for optimizing the structure of conical PDC teeth. Summary of the Invention

[0007] To solve the above problems of the prior art, to guide the selection of appropriate conical tooth structures during drilling in different formations, and to further improve the mechanical drilling speed and service life of PDC bits in hard formation drilling, the present invention provides a method for optimizing the structure of conical PDC teeth, the method comprising the following steps:

[0008] S1. Based on the formation parameters and the tip parameters of the conical PDC teeth, establish a contact stiffness calculation model to calculate the contact stiffness.

[0009] S2. Based on the formation parameters, construction parameters, bit parameters, and the contact stiffness, establish a conical tip radius calculation model to calculate the conical tip radius.

[0010] According to an embodiment of the present invention, the formation parameters include: the uniaxial compressive strength under the true in-situ stress of the formation, the Poisson's ratio of the formation, and the elastic modulus of the formation.

[0011] According to an embodiment of the present invention, the conical tip parameters include: the Poisson's ratio of the conical tip and the elastic modulus of the conical tip.

[0012] According to an embodiment of the present invention, the contact stiffness calculation model includes the following formula:

[0013]

[0014] Wherein, E represents the contact stiffness; v1 represents the Poisson's ratio of the formation; E1 represents the elastic modulus of the formation; v2 represents the Poisson's ratio of the conical tip; E2 represents the elastic modulus of the conical tip.

[0015] According to an embodiment of the present invention, the construction parameters include: the strength coefficient and the weight on bit borne by a single cutting tooth, and the value standard of the strength coefficient is to ensure that the cutting tooth penetrates into the formation.

[0016] According to an embodiment of the present invention, the bit parameters include: the radius of curvature at the position where the conical teeth are installed on the bit crown.

[0017] According to an embodiment of the present invention, the conical tip radius calculation model includes the following formula:

[0018]

[0019] Wherein, R2 represents the conical tip radius; k represents the strength coefficient; P represents the uniaxial compressive strength under the true in-situ stress of the formation; F represents the weight on bit borne by a single cutting tooth; E represents the contact stiffness; R represents the radius of curvature at the position where the conical teeth are installed on the bit crown.

[0020] According to an embodiment of the present invention, the method further includes:

[0021] S3. Based on the conical tip radius calculation model, analyze the variation law of the conical tip radius with the uniaxial compressive strength of the rock to guide the optimization scheme of the conical tip radius under different formation conditions.

[0022] According to another aspect of the present invention, there is also provided a storage medium, which includes a series of instructions for executing the method steps as described in any one of the above.

[0023] According to another aspect of the present invention, there is also provided a preferred device for the tapered PDC tooth structure, which executes a preferred method for the tapered PDC tooth structure as described in any one of the above, and the device includes:

[0024] A contact stiffness module, which is used to establish a contact stiffness calculation model based on formation parameters and the apex parameters of the tapered PDC tooth to calculate the contact stiffness;

[0025] An apex radius module, which is used to establish an apex radius calculation model based on the formation parameters, construction parameters, bit parameters and the contact stiffness to calculate the apex radius.

[0026] The preferred method and device for the tapered PDC tooth structure provided by the present invention have the following beneficial effects: It can provide scientific guidance for the optimization of the tapered PDC tooth, can combine the formation conditions to optimize the appropriate tapered tooth structure, and can avoid the situation that the tapered PDC tooth cannot penetrate in the hard formation or penetrates too deep in the plastic formation due to inappropriate structure. By optimizing the tapered PDC tooth through this method, it is expected to improve the mechanical drilling speed of the bit with tapered PDC teeth in extremely hard formations and extend the service life of the bit.

[0027] Other features and advantages of the present invention will be described in the following specification, and in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the structures specifically pointed out in the specification, claims and drawings. Description of the Drawings

[0028] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0029] Figure 1 Shows a flowchart of a preferred method for the tapered PDC tooth structure according to an embodiment of the present invention;

[0030] Figure 2 Shows a structure diagram of a tapered PDC tooth according to an embodiment of the present invention;

[0031] Figure 3 Shows a graph of the variation law of the apex radius with the uniaxial compressive strength of the rock according to an embodiment of the present invention; and

[0032] Figure 4 Shows a block diagram of a preferred device for the tapered PDC tooth structure according to an embodiment of the present invention. Detailed Embodiments

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further elaborates on the embodiments of the present invention in conjunction with the accompanying drawings.

[0034] The prior art (CN201910974754X) provides a design method for a tapered tooth PDC bit. It mainly obtains the drillability of the rock through laboratory experiments and determines the drilling conditions according to the drilling design requirements. Then, it determines the number of bit blades and the cutting tooth diameter according to the rock drillability, and then determines the bit diameter according to the drilling conditions. Finally, it determines the height difference between the tapered tooth and the PDC tooth according to the rock drillability and the bit structure parameters. However, the prior art (CN201910974754X) does not optimize the parameter of the apex radius of the tapered PDC tooth.

[0035] The prior art (Research on the cutting structure design of a rotary cutting PDC bit, Petroleum Machinery, 2020(7): 42-48.) studies the influence of cutting parameters on cutting efficiency through experiments and simulation methods. Through single-tooth rock-breaking experiments, it is determined that the optimal cutting angle of the tapered tooth is 20° under different cutting conditions; the cutting force and axial force will increase with the increase of the cutting depth; the rock-breaking speed of the tapered tooth will affect its cutting force and axial force. However, the prior art (Research on the cutting structure design of a rotary cutting PDC bit, Petroleum Machinery, 2020(7): 42-48.) does not optimize the parameter of the apex radius of the tapered PDC tooth.

[0036] Aiming at the defects existing in the above prior art and the problem that there is a lack of a scientific optimization method to guide the selection of tapered teeth when using a tapered tooth bit in hard formations, mainly relying on the experience of engineers, the present invention proposes a method and device for optimizing the structure of tapered PDC teeth. The present invention comprehensively considers the formation and the structural characteristics of the tapered teeth, which can not only ensure that the tapered teeth can effectively penetrate into the formation but also take into account ensuring the life of the tapered teeth, can make up for the current deficiencies in the optimization of tapered teeth, and improve the mechanical drilling speed and life of the tapered tooth bit.

[0037] Figure 1 Shows a flowchart of a method for optimizing the structure of tapered PDC teeth according to an embodiment of the present invention.

[0038] As Figure 1 shown, in step S101, based on the formation parameters and the apex parameters of the tapered PDC tooth, a contact stiffness calculation model is established to calculate the contact stiffness.

[0039] In one embodiment, the formation parameters include: the compressive strength under the true in-situ stress of the formation, the Poisson's ratio of the formation, and the elastic modulus of the formation. Further, the compressive strength under the true in-situ stress of the formation is obtained through laboratory experiment simulation or well logging interpretation. Specifically, the formation parameters are determined by the formation environment of the area to be drilled and can reflect the actual situation of the formation.

[0040] In one embodiment, the apex parameters include: the apex Poisson's ratio and the apex elastic modulus. Specifically, the apex parameters are determined by the material used for the apex and can reflect the actual situation of the apex. In one embodiment, as Figure 2 shown, a polycrystalline diamond layer is used as the apex.

[0041] In one embodiment, the contact stiffness calculation model includes the following formula:

[0042]

[0043] where E represents the contact stiffness; v1 represents the formation Poisson's ratio; E1 represents the formation elastic modulus; v2 represents the apex Poisson's ratio; and E2 represents the apex elastic modulus.

[0044] As Figure 1 shown, in step S102, based on the formation parameters, construction parameters, bit parameters, and contact stiffness, an apex radius calculation model is established to calculate the apex radius.

[0045] In one embodiment, the construction parameters include: the strength coefficient and the weight on bit borne by a single cutting tooth. The value standard of the strength coefficient is to ensure that the cutting tooth penetrates into the formation.

[0046] In one embodiment, the bit parameters include: the radius of curvature at the position where the conical teeth are installed on the bit crown.

[0047] In one embodiment, the apex radius calculation model includes the following formula:

[0048]

[0049] where R2 represents the apex radius; k represents the strength coefficient; P represents the compressive strength under the true in-situ stress of the formation; F represents the weight on bit borne by a single cutting tooth; E represents the contact stiffness; and R represents the radius of curvature at the position where the conical teeth are installed on the bit crown.

[0050] The apex radius calculation model provided by the present invention combines the conical tooth parameters and the formation parameters to be able to determine the appropriate radius of the apex.

[0051] As Figure 1 shown, in step S103, based on the apex radius calculation model, the variation law of the apex radius with the rock compressive strength is analyzed to guide the optimal selection scheme of the apex radius under different formation conditions.

[0052] In one embodiment, step a: Based on the apex radius calculation model, a scatter plot of the apex radius and the rock compressive strength is drawn; step b: Based on the scatter plot, data fitting is performed to obtain the variation law relationship of the apex radius with the rock compressive strength.

[0053] In practical applications, when designing conical PDC teeth, based on the relationship between the cone tip radius and the rock compressive strength, the cone tip radius suitable for the current formation to be drilled can be determined first, and then combined with the overall design of the drill bit to complete the design of other parameters of the drill bit, so as to design an efficient rock-breaking drill bit suitable for the current formation to be drilled.

[0054] In addition, in practical applications, when optimizing conical PDC teeth, based on the relationship between the cone tip radius and the rock compressive strength, the cone tip radius suitable for the current formation to be drilled can be determined, and then combined with other parameters to complete the optimization of conical PDC teeth, so as to select an efficient rock-breaking drill bit suitable for the current formation to be drilled.

[0055] In view of the current situation that the conical teeth have excellent rock-breaking effect in ultra-hard formations, but lack a scientific calculation method in the structural design of conical teeth, especially in determining the key parameter of the cone tip radius, the present invention provides a method for optimizing the structure of conical PDC teeth. By using the established calculation model of the cone tip radius combining the conical teeth and formation parameters, a suitable cone tip radius can be determined.

[0056] The present invention helps to improve the scientificity of the structural design of conical tooth drill bits, enhance the use effect of drill bits, and extend the service life of conical tooth drill bits. The present invention provides a scientific method for optimizing conical PDC teeth, which can further improve the drilling efficiency of drill bits with conical PDC teeth compared with the current process.

[0057] Figure 2 Shows a structural diagram of a conical PDC tooth according to an embodiment of the present invention. As Figure 2 shown, the conical PDC tooth includes a polycrystalline diamond layer 1 and a hard matrix 2. As Figure 2 shown, h represents the conical height, D represents the diameter of the cylindrical part, H represents the height of the cylindrical part, and α represents the conical angle.

[0058] Specifically, the cone tip parameters are determined by the material of the cone tip. Figure 2 Shown is a cone tip made of a polycrystalline diamond layer. When calculating the contact stiffness according to the contact stiffness calculation model, the Poisson's ratio and elastic modulus of the polycrystalline diamond layer need to be used.

[0059] Figure 3 Shows a graph of the variation law of the cone tip radius with the rock compressive strength according to an embodiment of the present invention.

[0060] In one embodiment, based on the characteristics of the Xujiahe ultra-hard formation, a method for optimizing the structure of conical PDC teeth provided by the present invention is used to calculate the maximum cone tip radius required for the conical teeth. The specific implementation method is as follows:

[0061] Step 1: Determine the formation parameters of Xujiahe Formation. Set the compressive strength P under the true in-situ stress of the formation to vary within the range of 100 - 500 MPa, the Poisson's ratio v1 of the formation to be 0.15, and the elastic modulus E1 of the formation to be 60 GPa;

[0062] Step 2: Determine the apex parameters of the conical PDC bit. The Poisson's ratio v2 of polycrystalline diamond is 10.075, and the elastic modulus E2 is 850 GPa;

[0063] Step 3: The single-tooth drilling pressure F is 8000 N, and the bit curvature radius R at the position where the conical teeth are installed is 0.4 m;

[0064] Step 4: According to the contact stiffness calculation model, the calculated value of the contact stiffness E is 102.3×10 6 , and the rock strength coefficient k is 2;

[0065] Step 5: Calculate the apex radius according to the apex radius calculation model, and then statistically analyze the variation law of the apex radius with the rock compressive strength. As Figure 3 shown, the higher the rock compressive strength, the smaller the apex radius, and the stronger the ability of the conical teeth to penetrate into the formation. During the structural design and optimization of the conical PDC bit, the appropriate apex radius can be selected according to the above variation law.

[0066] A method and device for optimizing the structure of a conical PDC bit provided by the present invention can also cooperate with a computer-readable storage medium. A computer program is stored on the storage medium, and the computer program is executed to run a method for optimizing the structure of a conical PDC bit. The computer program can run computer instructions, and the computer instructions include computer program code. The computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc.

[0067] The computer-readable storage medium can include: any entity or device capable of carrying computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0068] It should be noted that the content included in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable storage medium does not include electrical carrier signals and telecommunication signals.

[0069] Figure 4 Shows a structural block diagram of a device for optimizing the structure of a conical PDC bit according to an embodiment of the present invention.

[0070] As Figure 4 shown, a preferred device 400 for the structure of a conical PDC tooth includes a contact stiffness module 401 and a tip radius module 402.

[0071] The contact stiffness module 401 is used to establish a contact stiffness calculation model based on formation parameters and the tip parameters of the conical PDC tooth, so as to calculate the contact stiffness. The tip radius module 402 is used to establish a tip radius calculation model based on formation parameters, construction parameters, bit parameters and contact stiffness, so as to calculate the tip radius.

[0072] In one embodiment, a preferred device 400 for the structure of a conical PDC tooth further includes a preference module 403. The preference module 403 analyzes the variation law of the tip radius with the uniaxial compressive strength of the rock based on the tip radius calculation model, so as to guide the tip radius preference scheme under different formation conditions.

[0073] In summary, the present invention provides a method and device for optimizing the structure of a conical PDC tooth, which has the following beneficial effects: it can provide scientific guidance for the optimization of the conical PDC tooth, can combine the formation conditions to optimize the appropriate conical tooth structure, and can avoid the situation that the conical PDC tooth cannot penetrate into the hard formation or penetrates too deep into the plastic formation due to inappropriate structure. By optimizing the conical PDC tooth through this method, it is expected to improve the ROP of the bit with conical PDC teeth in extremely hard formations and extend the service life of the bit.

[0074] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant fields. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and do not mean to limit.

[0075] In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0076] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] As used herein, the phrase "an embodiment" or "embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "an embodiment" or "embodiments" throughout the specification are not necessarily all referring to the same embodiment.

[0078] The embodiments of the present invention are provided for purposes of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are chosen and described in order to best explain the principles of the invention and its practical application, and to enable those of ordinary skill in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0079] Although the embodiments disclosed in the present invention are as described above, the above content is only an embodiment adopted for the convenience of understanding the present invention, and is not intended to limit the present invention. Any person skilled in the art within the technical field to which the present invention pertains may make any modifications and variations in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A method for optimizing the structure of a conical PDC tooth, characterized in that, The method includes the following steps: S1. Based on the formation parameters and the apex parameters of the conical PDC bit, establish a contact stiffness calculation model to calculate the contact stiffness. The formation parameters include: the uniaxial compressive strength under the true in-situ stress of the formation, the Poisson's ratio of the formation, and the elastic modulus of the formation. The apex parameters include: the Poisson's ratio of the apex and the elastic modulus of the apex; S2. Based on the formation parameters, construction parameters, bit parameters, and the contact stiffness, establish a cone apex radius calculation model to calculate the cone apex radius. The bit parameters include: the radius of curvature at the position where the conical teeth are installed on the bit crown; The contact stiffness calculation model includes the following formula: where E represents the contact stiffness; v1 represents the Poisson's ratio of the formation; E1 represents the elastic modulus of the formation; v2 represents the Poisson's ratio of the apex; E2 represents the elastic modulus of the apex; The cone apex radius calculation model includes the following formula: where R2 represents the cone apex radius; k represents the strength coefficient; P represents the uniaxial compressive strength under the true in-situ stress of the formation; F represents the weight on bit borne by a single cutting tooth; E represents the contact stiffness; R represents the radius of curvature at the position where the conical teeth are installed on the bit crown.

2. The preferred method for a conical PDC tooth structure as described in claim 1, characterized in that, The construction parameters include: the strength coefficient and the weight on bit borne by a single cutting tooth. The value standard of the strength coefficient is to ensure that the cutting teeth penetrate into the formation.

3. The preferred method for a tapered PDC tooth structure as claimed in claim 1, wherein, The method further includes: S3. Based on the cone apex radius calculation model, analyze the variation law of the cone apex radius with the rock compressive strength to guide the optimization scheme of the cone apex radius under different formation conditions.

4. A storage medium, characterized in that, It includes a series of instructions for executing the method steps described in any one of claims 1-3.

5. A preferred device for a conical PDC tooth structure, characterized in that, Execute a method for optimizing the structure of a conical PDC bit described in any one of claims 1-3. The device includes: A contact stiffness module, which is used to establish a contact stiffness calculation model based on the formation parameters and the apex parameters of the conical PDC bit to calculate the contact stiffness; A cone apex radius module, which is used to establish a cone apex radius calculation model based on the formation parameters, construction parameters, bit parameters, and the contact stiffness to calculate the cone apex radius.

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