A variable diameter two-stage drill bit and drilling method suitable for viscoplastic formations

Abstract

The present invention discloses a variable diameter two-stage drill bit and drilling method suitable for viscoplastic formations, belonging to the field of oil and gas drilling engineering technology, including a drill bit body; a plurality of reaming blades are arranged on the side of the drill bit body, a force storage spring is arranged at the drill end of the drill bit body, and a pilot drill bit body is arranged at the other end of the force storage spring; the reaming blades are slidably matched with the drill bit body, and the reaming blades and the pilot drill bit body are slidably matched along the radial direction of the drill bit body; when the force storage spring pushes the pilot drill bit body away from the drill bit body, all the reaming blades follow the pilot drill bit body to move axially while moving radially inward; when the pilot drill bit body compresses the force storage spring to move closer to the drill bit body, all the reaming blades follow the pilot drill bit body to move axially while moving radially outward. The present invention can realize the extension or contraction of the reaming blades under the cooperation of the bit pressure, so that the drill bit can automatically adjust the diameter; and the overall structure is simple and the reliability is high.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas drilling engineering, and particularly relates to a variable-diameter two-stage drill bit suitable for viscoplastic formations and a drilling method. Background Art

[0002] In the field of oil and gas engineering, the continuous development of drilling technology is of great significance to improving the extraction efficiency of oil and gas reservoirs and reducing drilling costs. However, during the drilling process, the complexity of the formation often brings many challenges to drilling operations, especially in viscoplastic formations. Due to problems such as easy deformation of the formation, shrinkage of the wellbore, and difficulty in removing cuttings, conventional drilling tools are difficult to ensure efficient and stable drilling results, and may even lead to serious consequences such as drill bit sticking and wellbore instability. Therefore, the development of efficient and stable drilling tools and supporting drilling methods for viscoplastic formations has become an important research direction in the industry. Currently, the following two types of drill bits are mainly used in drilling operations in viscoplastic formations:

[0003] The first approach involves drilling with conventional drill bits, such as traditional PDC (polycrystalline diamond compact) or roller cone bits. However, these bits are susceptible to borehole shrinkage in viscoplastic formations, resulting in a reduction in wellbore dimensions and an increased likelihood of downhole complications. Furthermore, these bits typically lack adaptive diameter adjustment, making them inflexible in responding to changing formation conditions.

[0004] The second method involves drilling with expandable drill bits. These bits are mechanically or hydraulically driven and expandable to accommodate varying well diameters. However, these drill bits often have complex structures and low reliability. Mechanical failures can occur during extended drilling, impacting drilling stability. Furthermore, the expansion mechanism is difficult to control, making efficient hole expansion difficult. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a variable diameter two-stage drill bit suitable for viscoplastic formations.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A variable diameter two-stage drill bit suitable for viscoplastic formations, comprising a drill bit body;

[0008] A plurality of reaming blades are evenly arranged on the side surface of the drill body in the circumferential direction, a force storage spring is fixedly arranged at the drill end of the drill body, the force storage spring can be compressed and stored in the axial direction of the drill body, and the other end of the force storage spring is fixedly arranged on the pilot drill body;

[0009] The reaming blades are in sliding cooperation with the drill bit body, and the reaming blades are in sliding cooperation with the pilot drill bit body along the radial direction of the drill bit body;

[0010] When the force storage spring pushes the pilot drill body away from the drill body, all the reaming blades follow the pilot drill body to move axially and move radially inward; when the pilot drill body compresses the force storage spring and moves closer to the drill body, all the reaming blades follow the pilot drill body to move axially and move radially outward;

[0011] A plurality of reaming cutting teeth are arranged on the reaming blade along the generatrix direction, and the pilot drill bit body is provided with pilot cutting teeth.

[0012] Preferably, a drilling fluid collection chamber is provided in the middle of the drill bit body, and the drilling fluid collection chamber is connected to the drill string connection end;

[0013] A circumferential flow channel connected to the drilling fluid collection chamber is provided on the drill bit body between adjacent reaming blades, and a circumferential nozzle is provided at the radial outer end of the circumferential flow channel.

[0014] Preferably, an eccentric flow channel penetrating to the drilling fluid collection chamber is provided on the end surface of the drill bit body facing the pilot drill bit body, and the central axis of the eccentric flow channel is in a non-planar linear relationship with the central axis of the drill bit body.

[0015] Preferably, a through pilot drill flow passage is provided on the pilot drill bit body, and a pilot drill nozzle is provided in the pilot drill flow passage.

[0016] Preferably, a plurality of pilot drill blades are evenly arranged on the pilot drill body along the circumferential direction, and the pilot cutting teeth are arranged on the pilot drill blades and a plurality of them are arranged along the generatrix direction.

[0017] Preferably, ends of all pilot drill blades away from the drill body are close to each other, and a central conical cutting tooth is provided at the center where all pilot drill blades are close to each other.

[0018] Preferably, a plurality of radial slide rails corresponding to the reaming blades are provided along the circumferential direction on the end surface of the pilot drill bit body facing the drill bit body;

[0019] The end surface of the reaming blade facing the pilot drill body is provided with a radial slide groove which is radially slidably matched with the corresponding radial slide rail.

[0020] Preferably, a plurality of axial sliding grooves corresponding to the reaming blades are provided on the side surface of the drill bit body along the circumferential direction;

[0021] An axial slide rail is provided on the side of the reaming blade facing the drill bit body and is slidably matched with the corresponding axial slide groove;

[0022] The distance between the end of the axial slide groove close to the pilot drill bit body and the central axis of the drill bit body is smaller than the distance between the end of the axial slide groove away from the pilot drill bit body and the central axis of the drill bit body.

[0023] Preferably, a thread is provided on the side of the drill bit body away from the pilot drill bit body.

[0024] The invention also discloses a drilling method suitable for viscoplastic formations.

[0025] A drilling method suitable for viscoplastic formations is implemented based on a variable diameter two-stage drill bit suitable for viscoplastic formations, and the drilling method comprises the following steps:

[0026] Step 1: During initial drilling, start the conventional drilling mode and perform conventional drilling at a low drilling pressure with the reamer blades in a retracted state.

[0027] Step 2: When the viscoplastic formation is reached, the reaming operation mode is started, the drilling pressure is increased, the pilot drill body compresses the storage spring close to the drill body, and all the reaming blades move axially along with the pilot drill body and move radially outward. The reaming blades are deployed outward to perform the reaming operation;

[0028] Step 3: After drilling in the viscoplastic formation is completed, the drilling pressure is reduced, the stored spring is extended to move the pilot drill bit away from the drill bit body, and all the reaming blades move axially along with the pilot drill bit body while moving radially inward. The reaming blades are retracted inward, and the conventional drilling mode is restored;

[0029] In the above process, the drilling fluid is distributed through the drilling fluid collection chamber and ejected through the circumferential nozzles and the pilot drill bit nozzle, carrying the crushed cuttings into the annulus;

[0030] When the reaming operation mode is turned on, the drilling fluid pump pressure is increased, the angular momentum of the drilling fluid in the eccentric flow channel is increased, and the drill bit generates circumferential vibration during the reaming operation, thereby improving the reaming effect.

[0031] The beneficial effects of the present invention are:

[0032] (1) The present invention can achieve the extension or retraction of the reaming blades by coordinating the reaming blades with the drill bit body, the reaming blades with the pilot drill bit body, and the arrangement of a force storage spring between the drill bit body and the pilot drill bit body, in cooperation with the drilling pressure, so that the drill bit can automatically adjust its diameter to adapt to different formation conditions, thereby improving the flexibility and stability of drilling; and the overall structure is simple and reliable, and the diameter expansion is achieved by using a force storage spring in combination with the drilling pressure, thereby avoiding the complexity of mechanical or hydraulic diameter expansion devices and improving the durability and stability of the drill bit.

[0033] (2) In the present invention, the setting of the eccentric flow channel causes the drilling fluid to generate angular momentum, causing the drill bit to generate circumferential vibration during the reaming operation, thereby reducing the adhesion between the drill tool and the formation and improving the reaming efficiency.

[0034] (3) In the present invention, the expansion of the reamer blades and the circumferential vibration caused by the eccentric flow channel are combined to weaken the wrapping effect of the viscoplastic formation on the drill bit, effectively reduce the drilling resistance, reduce the risk of the drill bit getting stuck, and improve the drilling safety.

[0035] (4) The present invention is applicable to viscoplastic formations, soft-hard alternating formations and other complex formations prone to wellbore shrinkage, which improves the applicability of drilling technology and has broad engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings in the specification, which constitute a part of this application, are used to provide further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute improper limitations on this application.

[0037] Figure 1 The present invention is a schematic structural diagram of a variable diameter two-stage drill bit suitable for viscoplastic formations. Figure 1 ;

[0038] Figure 2 The present invention is a schematic structural diagram of a variable diameter two-stage drill bit suitable for viscoplastic formations. Figure 2 ;

[0039] Figure 3 This is a schematic front view of the structure of a variable diameter two-stage drill bit suitable for viscoplastic formations according to the present invention;

[0040] Figure 4 yes Figure 3 AA section view;

[0041] Figure 5 2. It is a schematic bottom view of the structure of a variable diameter two-stage drill bit suitable for viscoplastic formations according to the present invention;

[0042] Figure 6 yes Figure 5 BB cross-sectional view;

[0043] in:

[0044] 1-drill bit body, 2-reaming blade, 3-storage spring, 4-reaming cutting tooth, 5-pilot cutting tooth, 6-axial slide, 7-axial slide rail, 8-drilling fluid collection chamber, 9-circumferential flow channel, 10-eccentric flow channel, 11-pilot drill blade, 12-center conical cutting tooth, 13-pilot drill flow channel, 14-radial slide rail, 15-radial slide. DETAILED DESCRIPTION

[0045] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0046] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0047] In the present invention, the directions or positional relationships indicated by terms such as "upper", "lower", "bottom", and "top" are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention. They do not specifically refer to any part or element in the present invention and cannot be understood as limitations on the present invention.

[0048] In the present invention, terms such as "connected" and "connection" should be interpreted broadly to mean a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediary. Relevant researchers or technicians in this field may determine the specific meanings of these terms in the present invention based on specific circumstances, and they should not be construed as limitations on the present invention.

[0049] The present invention will be further described below with reference to the accompanying drawings and examples.

[0050] Example 1:

[0051] like Figures 1-6 As shown, a variable diameter dual-stage drill bit suitable for viscoplastic formations includes a drill bit body 1;

[0052] A plurality of reaming blades 2 are evenly arranged on the side surface of the drill body 1 along the circumferential direction. A force storage spring 3 is fixedly arranged at the drill end of the drill body 1. The force storage spring 3 can be compressed and stored in the axial direction of the drill body 1. The other end of the force storage spring 3 is fixedly arranged on the pilot drill body.

[0053] The reaming blades 2 are in sliding cooperation with the drill bit body 1, and the reaming blades 2 are in sliding cooperation with the pilot drill bit body along the radial direction of the drill bit body 1, so that the pilot drill bit body and the reaming blades 2 are linked together;

[0054] When the force storage spring 3 pushes the pilot drill body away from the drill body 1, all the reaming blades 2 move axially with the pilot drill body and move radially inward, thereby realizing the inward contraction of the reaming blades 2; when the pilot drill body compresses the force storage spring 3 and moves closer to the drill body 1, all the reaming blades 2 move axially with the pilot drill body and move radially outward, thereby realizing the outward expansion of the reaming blades 2;

[0055] Several reaming cutting teeth 4 are arranged along the generatrix on the reaming blades 2. These teeth are mounted on the blades 2 and, when deployed, contact the wellbore wall to perform reaming operations. Pilot cutting teeth 5 are also provided on the pilot drill bit body. The reaming blades 2 and cutting teeth 4 can be manufactured from highly wear-resistant alloys or PDC materials, improving durability and erosion resistance, thereby extending the service life of the drill bit.

[0056] Preferably, a drilling fluid collection chamber 8 is provided in the middle of the drill bit body 1, and the drilling fluid collection chamber 8 is connected to the drill string connection end; the drilling fluid collection chamber 8 is used to collect and distribute the drilling fluid so that it can flow evenly to each nozzle and flow channel, thereby optimizing the flow field distribution of the drilling fluid;

[0057] A circumferential flow channel 9 connected to the drilling fluid collection chamber 8 is provided on the drill bit body 1 between adjacent reaming blades 2, and a circumferential nozzle is provided at the radial outer end of the circumferential flow channel 9; the circumferential nozzle is used to spray high-pressure drilling fluid to enhance the cooling effect of the drill bit, assist in removing cutting debris, and improve drilling efficiency.

[0058] Preferably, an eccentric flow channel 10 extending through the drilling fluid collection chamber 8 is provided on the end face of the drill bit body 1 facing the pilot drill bit body. The central axis of the eccentric flow channel 10 is in a non-planar linear relationship with the central axis of the drill bit body 1. During the reaming operation, by adjusting the drilling fluid pump pressure, the drilling fluid gains angular momentum when flowing through the eccentric flow channel 10, thereby generating circumferential vibration, enhancing the cutting ability of the reaming blades 2, and improving reaming efficiency. The distance between the intersection of the central axis of the eccentric flow channel 10 and the bottom end face of the drilling fluid collection chamber 8 and the central axis of the drill bit body 1 is less than the distance between the intersection of the central axis of the eccentric flow channel 10 and the bottom end face of the drill bit body 1 and the central axis of the drill bit body 1.

[0059] Preferably, the pilot drill bit body is provided with a through pilot drill bit flow channel 13, and a pilot drill bit nozzle is provided in the pilot drill bit flow channel 13. The pilot drill bit nozzle is used to spray drilling fluid, improve the cooling effect of the pilot drill bit blade 11, and help discharge rock cuttings.

[0060] Preferably, the pilot drill bit body is uniformly provided with a plurality of pilot drill blades 11 along the circumference. The pilot cutters 5 are arranged on the pilot drill blades 11 in a plurality along the generatrix. The pilot drill blades 11 are primarily used for initial wellbore drilling. The pilot cutters 5 are arranged on the pilot drill blades 11 to perform initial drilling of the formation. A pilot drill flow channel 13 is provided through the pilot drill bit body between adjacent pilot drill blades 11.

[0061] Preferably, the ends of all pilot drill blades 11 away from the drill bit body 1 are close together, and a central conical cutting tooth 12 is provided at the center of all pilot drill blades 11. The central conical cutting tooth 12 is located at the center of the drill bit to ensure effective crushing of the bottom hole rock during drilling and improve drilling efficiency.

[0062] Preferably, a plurality of radial slide rails 14 corresponding to the reaming blades 2 are provided along the circumferential direction on the end surface of the pilot drill body facing the drill body 1;

[0063] The end surface of the reaming blade 2 facing the pilot drill body is provided with a radial slide groove 15 which is radially slidably matched with the corresponding radial slide rail 14.

[0064] Preferably, a plurality of axial sliding grooves 6 corresponding to the reaming blades 2 are provided on the side surface of the drill body 1 along the circumferential direction;

[0065] An axial slide rail 7 is provided on the side of the reaming blade 2 facing the drill bit body 1 and is slidably matched with the corresponding axial slide groove 6;

[0066] The distance between the end of the axial slot 6 close to the pilot drill body and the central axis of the drill body 1 is smaller than the distance between the end of the axial slot 6 away from the pilot drill body and the central axis of the drill body 1 .

[0067] Preferably, a thread is provided on the side of the drill bit body 1 away from the pilot drill bit body for connection with a drill string.

[0068] Example 2:

[0069] A drilling method suitable for viscoplastic formations is implemented based on the variable diameter two-stage drill bit suitable for viscoplastic formations in Example 1, and the drilling method comprises the following steps:

[0070] Step 1: During initial drilling, start the conventional drilling mode and perform conventional drilling at a low drilling pressure, with the reaming blade 2 in a retracted state;

[0071] Step 2: When the viscoplastic formation is reached, the reaming operation mode is started, the drilling pressure is increased, the pilot drill body compresses the storage spring 3 and moves close to the drill body 1, and all the reaming blades 2 move axially with the pilot drill body and move radially outward. The reaming blades 2 are deployed outward to perform the reaming operation;

[0072] Step 3: Drilling in the viscoplastic formation is completed, the drilling pressure is reduced, and the force storage spring 3 is extended to move the pilot drill bit away from the drill bit body 1. All the reaming blades 2 move axially along with the pilot drill bit body and move radially inward. The reaming blades 2 are retracted inward, and the normal drilling mode is restored;

[0073] During the above process, the drilling fluid is distributed through the drilling fluid collection chamber 8 and ejected through the circumferential nozzles and the pilot drill nozzle, carrying the crushed rock cuttings into the annulus;

[0074] When the reaming operation mode is turned on, the drilling fluid pump pressure is increased, the angular momentum of the drilling fluid in the eccentric flow channel 10 is increased, and the drill bit generates circumferential vibration during the reaming operation, thereby improving the reaming effect; in addition, increasing the drilling fluid pump pressure can further reduce the adhesion between the drill tool and the viscoplastic formation, thereby improving drilling stability.

[0075] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not a limitation of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A variable diameter two-stage drill bit suitable for viscoplastic formations, comprising a drill bit body; characterized in that: A plurality of reaming blades are evenly arranged on the side surface of the drill body in the circumferential direction, a force storage spring is fixedly arranged at the drill end of the drill body, the force storage spring can be compressed and stored in the axial direction of the drill body, and the other end of the force storage spring is fixedly arranged on the pilot drill body; The reaming blades are in sliding cooperation with the drill bit body, and the reaming blades are in sliding cooperation with the pilot drill bit body along the radial direction of the drill bit body; When the force storage spring pushes the pilot drill body away from the drill body, all the reaming blades follow the pilot drill body to move axially and move radially inward; when the pilot drill body compresses the force storage spring and moves closer to the drill body, all the reaming blades follow the pilot drill body to move axially and move radially outward; A plurality of reaming cutting teeth are arranged on the reaming blade along the generatrix direction, and pilot cutting teeth are provided on the pilot drill body; A drilling fluid collection chamber is provided in the middle of the drill bit body, and the drilling fluid collection chamber passes through to the drill string connection end; An eccentric flow channel is provided on the end surface of the drill bit body facing the pilot drill bit body and passes through the drilling fluid collection chamber, and the central axis of the eccentric flow channel is in a non-planar linear relationship with the central axis of the drill bit body; When the reaming operation mode is turned on, the drilling fluid pump pressure is increased, the angular momentum of the drilling fluid in the eccentric flow channel is increased, and the drill bit generates circumferential vibration during the reaming operation, thereby improving the reaming effect.

2. The variable diameter two-stage drill bit suitable for viscoplastic formations according to claim 1, characterized in that: A circumferential flow channel connected to the drilling fluid collection chamber is provided on the drill bit body between adjacent reaming blades, and a circumferential nozzle is provided at the radial outer end of the circumferential flow channel.

3. The variable diameter two-stage drill bit suitable for viscoplastic formations according to claim 2, characterized in that: A through pilot drill flow passage is provided on the pilot drill body, and a pilot drill nozzle is provided in the pilot drill flow passage.

4. The variable diameter two-stage drill bit suitable for viscoplastic formations according to claim 3, characterized in that: A plurality of pilot drill blades are evenly arranged on the pilot drill body along the circumferential direction, and a plurality of pilot cutting teeth are arranged on the pilot drill blades and along the generatrix direction.

5. The variable diameter dual-stage drill bit suitable for viscoplastic formations according to claim 4, characterized in that: Ends of all pilot drill blades away from the drill body are close to each other, and a central conical cutting tooth is arranged at the center where all pilot drill blades are close to each other.

6. The variable diameter dual-stage drill bit suitable for viscoplastic formations according to claim 3, characterized in that: The pilot drill body is provided with a plurality of radial slide rails corresponding to the reaming blades in a circumferential direction on the end surface facing the drill body; The end surface of the reaming blade facing the pilot drill body is provided with a radial slide groove which is radially slidably matched with the corresponding radial slide rail.

7. The variable diameter dual-stage drill bit suitable for viscoplastic formations according to claim 3, characterized in that: A plurality of axial sliding grooves corresponding to the reaming blades are provided on the side surface of the drill bit body along the circumferential direction; An axial slide rail is provided on the side of the reaming blade facing the drill bit body and is slidably matched with the corresponding axial slide groove; The distance between the end of the axial slide groove close to the pilot drill bit body and the central axis of the drill bit body is smaller than the distance between the end of the axial slide groove away from the pilot drill bit body and the central axis of the drill bit body.

8. The variable diameter dual-stage drill bit suitable for viscoplastic formations according to claim 3, characterized in that: A thread is provided on the side of the drill bit body away from the pilot drill bit body.

9. A drilling method suitable for viscoplastic formations, implemented based on the variable diameter two-stage drill bit suitable for viscoplastic formations according to any one of claims 3 to 8, characterized in that: The drilling method comprises the following steps: Step 1: During initial drilling, start the conventional drilling mode and perform conventional drilling at a low drilling pressure with the reamer blades in a retracted state. Step 2: When the viscoplastic formation is reached, the reaming operation mode is started, the drilling pressure is increased, the pilot drill body compresses the storage spring close to the drill body, and all the reaming blades move axially along with the pilot drill body and move radially outward. The reaming blades are deployed outward to perform the reaming operation; Step 3: After drilling in the viscoplastic formation is completed, the drilling pressure is reduced, the stored spring is extended to move the pilot drill bit away from the drill bit body, and all the reaming blades move axially along with the pilot drill bit body while moving radially inward. The reaming blades are retracted inward, and the conventional drilling mode is restored; In the above process, the drilling fluid is distributed through the drilling fluid collection chamber and ejected through the circumferential nozzles and the pilot drill bit nozzle, carrying the crushed cuttings into the annulus; When the reaming operation mode is turned on, the drilling fluid pump pressure is increased, the angular momentum of the drilling fluid in the eccentric flow channel is increased, and the drill bit generates circumferential vibration during the reaming operation, thereby improving the reaming effect.

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