CN114592796B - PDC drill bit suitable for tight mudstone stratum - Google Patents

Abstract

The invention belongs to the field of drilling equipment, and in particular relates to a PDC drill bit suitable for tight mudstone formations, comprising an outer cutting unit; an inner cutting unit; a connecting rod; a locking mechanism and a diamond composite cutting tooth. It moves in the circumferential direction, and realizes the locking and release between the two cutting units through the locking mechanism. When cutting the fluffy formation, the inner cutting unit acts as a pilot bit and protrudes in front of the outer cutting unit, and the outer cutting unit acts as a reaming bit. The area around the inner cutting unit is reamed to improve the overall drilling capacity of the drill bit. At this time, there is a large gap between the inner blade and the outer blade, which can avoid the mud bag at the front end of the bit; when cutting tight mudstone formations, The inner cutting unit and the outer cutting unit can be kept flush to disperse the cutting stress, ensure the stable drilling process and avoid chipping. The invention can switch back and forth between the two working stations, so as to adapt to the complex formation environment where the soft and hard are interlaced.

Description

A PDC bit suitable for tight mudstone formations

technical field

The invention belongs to the field of drilling equipment, in particular to a PDC drill bit suitable for tight mudstone formations.

Background technique

PDC drill bits are also called polycrystalline diamond composite drill bits, which generally include a drill bit body and a polycrystalline diamond composite sheet embedded in the end of the drill bit body. Coated cutting parts. Traditional PDC bits are generally of one-piece structure, and the relative position of each cutter is generally fixed. However, in actual use, it is found that for different geological layers, the cutting efficiency of the bit is greatly affected by the distribution of cutters. In the upper rock strata, using a smaller cutting area can significantly increase the drilling speed, while using a larger cutting area will lead to a decrease in the drilling speed and easy occurrence of mud bags at the end of the drill bit; while for tight mudstone strata, using a relatively small cutting area will reduce the drilling speed. A large cutting area is more beneficial to the stable feed of the drill. Since the drill bits in the prior art are all of one-piece structure, the drill bits need to be replaced repeatedly when facing different rock formations, which seriously affects the drilling efficiency.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a PDC drill bit suitable for tight mudstone formations which can improve drilling efficiency.

For achieving the above-mentioned purpose and other related purposes, the present invention provides the following technical solutions:

A PDC bit suitable for tight mudstone formations, comprising:

The outer cutting unit includes an outer blade holder, the center of the outer blade holder is provided with a central hole passing through the outer blade holder, the crown of the outer blade holder is provided with an outer blade wing, and the outer blade blade extends from the The edge of the central hole extends to the side surface of the outer knife seat, and a plurality of the outer knife wings are arranged at intervals along the circumferential direction of the outer knife seat;

The inner cutting unit includes an inner knife seat, the crown of the inner knife seat is provided with an inner knife wing, the inner knife wing is only distributed on the end face of the inner knife seat, and the inner knife wing is along the inner knife seat. The inner tool seat is movably arranged in the center hole of the outer tool seat in the axial direction, so that the inner cutting unit and the outer cutting unit can be switched between the following two stations : Station 1, the inner blade protrudes out a preset distance in the axial direction relative to the outer blade; and Station 2, the inner blade is flush with the crown of the outer blade; The inner tool holder and the outer tool holder are connected in a synchronous rotation along the circumferential direction;

a connecting rod, one end of the connecting rod is provided with a connecting part for connecting the drill rod, and the other end is connected with the inner tool seat, so as to drive the inner tool seat to feed in the axial direction and rotate in the circumferential direction;

a locking mechanism, arranged between the inner tool seat and the outer tool seat, the locking mechanism is assembled to have a locking station and an unlocking station, when the locking mechanism is located at the locking station , the outer cutting unit and the inner cutting unit in the second station can be kept in the second station, so that the outer cutting unit can be synchronized with the inner cutting unit in the second station state Feeding; when the locking mechanism is at the unlocking position, the outer cutting unit can move freely relative to the inner cutting unit in the axial direction, so that when the inner cutting unit feeds, the outer cutting unit can Switch to the station one under the blocking of the rock formation, and keep it at the station one;

The outer blade and the inner blade are provided with diamond composite cutting teeth.

In an optional embodiment of the present invention, a blind hole is provided on an end of the inner knife seat away from the inner knife wing, and the connecting rod is inserted into the blind hole; the locking mechanism includes a movable The ball is arranged on the side wall of the inner tool seat, and the annular groove is arranged on the inner wall of the outer tool seat. When the inner cutting unit and the outer cutting unit are in the second station, the ball and the outer cutting unit are in the second position. The annular grooves are aligned, the side wall of the inner tool seat is provided with a radial hole arranged through the side wall, and the ball is movably arranged in the radial hole along the radial direction of the inner tool seat, so The diameter of the ball is larger than the thickness of the side wall of the inner tool seat, the connecting rod is provided with a groove at the position corresponding to the ball, and the bottom surface of the groove and the outer wall of the connecting rod smoothly transition. The connecting rod is rotatably matched with the inner tool seat within a preset angle range, so that the connecting rod and the inner tool seat can be switched between the first angle interval and the second angle interval. When the rod and the inner cutter seat are located in the first angle section, the ball is opposite to the groove, and the inner side of the ball can be partially accommodated in the groove, so that the outer side of the ball avoids the ring groove, the locking mechanism is in the unlocking position at this time; when the connecting rod and the inner tool seat are located in the second angle range, the groove and the ball are staggered from each other in the circumferential direction, so that all the The ball is pushed into the ring groove by the connecting rod, and the locking mechanism is in the locking position at this time; when the connecting rod rotates in the first direction relative to the inner tool seat, The switching of the two from the first angle interval to the second angle interval is realized, and the first direction is the cutting direction of the drill bit.

In an optional embodiment of the present invention, the outer wall of the connecting rod is provided with protruding teeth, and the inner wall of the inner tool seat is provided with a first arc-shaped groove and a second arc-shaped groove that cooperate with the protruding teeth The first arc-shaped groove and the second arc-shaped groove are arranged at intervals along the axial direction of the inner tool seat, and are communicated with each other through an axial groove, and the connecting rod is axially connected to the inner tool seat. The tool seat is movably connected, so that the protruding teeth are switched between the first arc-shaped groove and the second arc-shaped groove, and when the protruding teeth are located in the first arc-shaped groove, the The connecting rod can move between the first angle section and the second angle section, and when the protruding teeth are located in the second arc groove, the connecting rod can only move in the first angle section Internal movement; when the connecting rod moves relative to the inner tool seat along the first linear direction, the protruding teeth can be moved from the first arc-shaped groove to the second arc-shaped groove, the The first linear direction is the feed direction of the drill.

In an optional embodiment of the present invention, the connecting rod is internally provided with a main water channel, a first liquid separation chamber is formed between the inner wall of the outer knife holder and the outer wall of the connecting rod, and the end of the connecting rod is A second liquid-separating cavity is formed between it and the inner knife seat, and a first through hole and a second through-hole respectively communicating with the first and second liquid-separating cavity are provided on the side wall of the connecting rod; A first flow channel is arranged inside the outer knife seat, the liquid inlet of the first flow channel is communicated with the first liquid separation chamber, and the liquid outlet of the first flow channel is formed on the crown of the outer knife seat, And the liquid outlet is located between two adjacent outer knife wings; the inner knife seat is provided with a second flow channel, the liquid inlet of the second flow channel is communicated with the second liquid separation cavity, and the The liquid outlet of the second flow channel is formed at the end of the inner blade seat, and the liquid outlet is located between two adjacent inner blade wings.

In an optional embodiment of the present invention, a convex ring is formed on the connecting rod, a first step portion and a second step portion are formed on the inner wall of the outer tool holder, and the inner ring surface of the first step portion is formed Fitted with the outer wall of the connecting rod, the inner ring surface of the second step portion is spaced apart from the outer wall of the connecting rod, and the first step portion and the second step portion are located close to each other relative to the convex ring. On one side of the crown portion of the outer knife seat, the convex ring, the inner wall of the outer knife seat, the first step portion and the second step portion together form the first liquid separation chamber, and when the first liquid separation chamber is filled with When liquid is injected, a thrust in the first linear direction can be generated on the outer cutter seat.

In an optional embodiment of the present invention, the liquid inlet of the first flow channel is formed on the inner annular surface of the second step portion.

In an optional embodiment of the present invention, a closing mechanism is provided between the connecting rod and the inner knife seat, and the closing mechanism is assembled so that when the connecting rod and the inner knife seat are in a first opposite position When the angle is preset, the water channel between the main water channel and the second liquid separation chamber can be disconnected, the first relative preset angle is located in the first angle range, and when the connecting rod is connected to the When the inner knife seat is at other relative angles within the first angle section and the second angle section, the water channel between the main water channel and the second liquid separation chamber can be communicated.

In an optional embodiment of the present invention, the closing mechanism includes an axial slot opened on the inner wall of the inner tool seat, when the connecting rod and the inner tool seat are in the first angle range and the second angle At other relative angles other than the first relative preset angle within the angle interval, the second through hole is opposite to the axial slot, and at this time, the second through hole passes through the axial slot and the The second liquid separation chamber is communicated; when the connecting rod and the inner cutter seat are at the first relative preset angle, the second through hole and the axial groove are staggered, and at this time the second through hole Disconnected from the second dispensing chamber.

In an optional embodiment of the present invention, a bar-shaped key is formed on the inner knife seat extending from the outer end of the inner knife wing to the side wall of the inner knife seat, and the inner wall of the outer knife seat is formed with a bar key. A keyway is formed to cooperate with the bar key.

In an optional embodiment of the present invention, the number of the outer blades is greater than the number of the inner blades, and each inner blade corresponds to an outer blade aligned with it in the radial direction. The inner end of the outer blade that is aligned with the inner blade is provided with an auxiliary liquid jetting port, the auxiliary liquid jetting port is disposed toward the outer wall of the bar key, and the auxiliary liquid jetting port is communicated with the first flow channel.

The technical effect of the present invention is as follows: the present invention adopts a combined drill bit with movable parts, wherein the outer cutting unit can move in the circumferential direction relative to the inner cutting unit, and the locking and release between the two cutting units are realized by the locking mechanism, When cutting fluffy formations, the inner cutting unit acts as a pilot bit and protrudes in front of the outer cutting unit, while the outer cutting unit acts as a reaming bit to ream the area around the inner cutting unit, improving the overall drilling capacity of the bit. There is a large gap between the blade and the outer blade, which can avoid the mud bag at the front end of the drill bit; when cutting tight mudstone formations, the inner cutting unit and the outer cutting unit can be kept flush, so as to disperse the cutting stress and ensure the stability of the drilling process , to avoid chipping. The invention can switch back and forth between the two working stations, so as to adapt to the complex formation environment where the soft and hard are interlaced.

Description of drawings

1 is a perspective view of a PDC drill bit provided by an embodiment of the present invention when it is located at station one;

2 is a front view of the PDC drill bit provided by an embodiment of the present invention when it is located at station one;

3 is an end view of a PDC drill bit provided by an embodiment of the present invention;

Fig. 4 is the A-A sectional view of Fig. 3;

Fig. 5 is B1-B1 sectional view of Fig. 4;

Fig. 6 is C1-C1 sectional view of Fig. 4;

Fig. 7 is D1-D1 sectional view of Fig. 4;

Fig. 8 is the E1-E1 sectional view of Fig. 4;

9 is a cross-sectional view of the intermediate state of the PDC drill bit provided by the embodiment of the present invention, and the cutting position is the same as that of FIG. 5;

10 is a cross-sectional view of the intermediate state of the PDC drill bit provided by the embodiment of the present invention, and the cutting position is the same as that of FIG. 6;

11 is a cross-sectional view of the intermediate state of the PDC drill bit provided by the embodiment of the present invention, and the cutting position is the same as that of FIG. 7;

12 is a cross-sectional view of the intermediate state of the PDC drill bit provided by the embodiment of the present invention, and the cutting position is the same as that of FIG. 8;

13 is a perspective view of the PDC drill bit provided by the embodiment of the present invention when it is located at the second station;

14 is a front view of the PDC drill bit provided by the embodiment of the present invention when it is located at the second station;

15 is a cross-sectional view of the PDC drill bit provided by the embodiment of the present invention when it is located at the second station;

Fig. 16 is the B2-B2 sectional view of Fig. 15;

Fig. 17 is the C2-C2 sectional view of Fig. 15;

Fig. 18 is the D2-D2 sectional view of Fig. 15;

Fig. 19 is the E2-E2 sectional view of Fig. 15;

20 is an exploded view of a PDC drill bit provided by an embodiment of the present invention, in which the outer cutting unit and the inner cutting unit are in a half-section state;

The meanings of the reference symbols are as follows: 10, outer knife seat; 11, outer knife wing; 101, first flow channel; 102, auxiliary liquid ejection port; 103, first liquid separation chamber; 12, ring groove; 13, first step part; 14, the second step part; 20, the inner knife seat; 21, the inner knife wing; 201, the second flow channel; 202, the bar key; 203, the second liquid separation chamber; 204, the axial groove; 22 , ball; 23, first arc groove; 24, second arc groove; 25, axial groove; 30, connecting rod; 301, main water channel; 31, connecting part; 311, external thread; 312, spline groove; 32, groove; 33, convex teeth; 34, first through hole; 35, second through hole; 36, convex ring.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other under the condition of no conflict.

It should be noted that the diagrams provided in the following embodiments are only used to illustrate the basic concept of the present invention in a schematic way, so the diagrams only show the components related to the present invention rather than the number, shape and For dimension drawing, the type, quantity and proportion of each component can be changed at will in actual implementation, and the component layout may also be more complicated.

See Figure 1-20, a PDC bit suitable for tight mudstone formations, including:

The outer cutting unit includes an outer tool seat 10, the center of the outer tool seat 10 is provided with a central hole penetrating the outer tool seat 10, the crown of the outer tool seat 10 is provided with an outer blade 11, and the outer The blade 11 extends from the edge of the central hole to the side surface of the outer blade holder 10 , and a plurality of the outer blade blades 11 are arranged at intervals along the circumference of the outer blade holder 10 ;

The inner cutting unit includes an inner cutter seat 20, the crown of the inner cutter seat 20 is provided with an inner cutter wing 21, the inner cutter wing 21 is only distributed on the end face of the inner cutter seat 20, the inner cutter wing 21 A plurality of inner tool seats 20 are arranged at intervals along the circumferential direction of the inner tool seat 20; the inner tool seat 20 is movably arranged in the central hole of the outer tool seat 10 in the axial direction, so that the inner cutting unit and the outer cutting unit The unit can be switched between the following two stations: station 1, where the inner blade 21 protrudes axially by a preset distance relative to the outer blade 11; and station 2, where the inner blade 21 and The crown of the outer blade 11 is flush, and the crown refers to the front end in the feeding direction of the drill bit; the inner blade holder 20 and the outer blade holder 10 are connected synchronously in the circumferential direction;

A connecting rod 30, one end of the connecting rod 30 is provided with a connecting portion 31 for connecting the drill rod, and the other end is connected with the inner tool seat 20 to drive the inner tool seat 20 to feed in the axial direction and in the circumferential direction turn;

The locking mechanism is arranged between the inner tool seat 20 and the outer tool seat 10. The locking mechanism is assembled to have a locking station and an unlocking station. When the locking mechanism is located in the locking station In the second position, the outer cutting unit and the inner cutting unit in the second station can be kept at the second station, so that the outer cutting unit can be in the second position with the inner cutting unit. The unit is fed synchronously; when the locking mechanism is in the unlocking position, the outer cutting unit can move freely relative to the inner cutting unit in the axial direction, so that when the inner cutting unit is fed, the outer cutting unit Can be switched to the first station under the blocking of the rock formation, and remain in the first station;

The outer blade 11 and the inner blade 21 are provided with diamond composite cutting teeth 40 .

The present invention adopts a combined drill bit with movable parts, wherein the outer cutting unit can move in the circumferential direction relative to the inner cutting unit, and the locking and releasing between the two cutting units are realized through the locking mechanism. The cutting unit acts as a pilot bit and protrudes in front of the outer cutting unit, and the outer cutting unit acts as a reaming bit to ream the area around the inner cutting unit, which improves the overall drilling capacity of the drill bit. At this time, the inner blade 21 and the outer blade There is a large gap between 11 and 11, which can avoid the mud bag at the front end of the drill bit; when cutting tight mudstone formations, the inner cutting unit and the outer cutting unit can be kept flush, thereby dispersing cutting stress, ensuring stable drilling process and avoiding chipping. The invention can switch back and forth between the two working stations, so as to adapt to the complex formation environment where the soft and hard are interlaced.

As shown in FIGS. 4 , 7 , 11 , 15 , 18 , and 20 , in a specific embodiment, a blind hole is provided on the end of the inner blade holder 20 away from the inner blade 21 , and the connecting rod 30 is inserted into the inner blade 20 . installed in the blind hole; the locking mechanism includes a ball 22 movably arranged on the side wall of the inner tool seat 20, and an annular groove 12 arranged on the inner wall of the outer tool seat 10, when the inner cutting When the unit and the outer cutting unit are in the second station, the balls 22 are aligned with the annular groove 12, and the side wall of the inner tool seat 20 is provided with a radial hole arranged through the side wall, so The balls 22 are movably arranged in the radial holes along the radial direction of the inner tool seat 20 . The diameter of the balls 22 is greater than the thickness of the side wall of the inner tool seat 20 . A groove 32 is provided at the corresponding position of the ball 22, and the bottom surface of the groove 32 smoothly transitions to the outer wall of the connecting rod 30, and the connecting rod 30 rotates with the inner tool seat 20 within a preset angle range In cooperation, the connecting rod 30 and the inner knife seat 20 can be switched between the first angle interval and the second angle interval, when the connecting rod 30 and the inner knife seat 20 are located in the first angle interval , the ball 22 is opposite to the groove 32, and the inner side of the ball 22 can be partially accommodated in the groove 32, so that the outer side of the ball 22 avoids the ring groove 12, and the lock The mechanism is in the unlocking position; when the connecting rod 30 and the inner tool seat 20 are located in the second angle range, the groove 32 and the ball 22 are staggered from each other in the circumferential direction, so that the ball 22 When the connecting rod 30 is pushed into the ring groove 12, the locking mechanism is in the locking position; when the connecting rod 30 rotates in the first direction relative to the inner tool seat 20 When , the switching of the two from the first angle interval to the second angle interval is realized, and the first direction is the cutting direction of the drill bit.

As shown in FIGS. 4-6 , 9 , 10 , 15-17 , and 20 , in a specific embodiment, convex teeth 33 are provided on the outer wall of the connecting rod 30 , and protruding teeth 33 are provided on the inner wall of the inner knife seat 20 . The first arc-shaped groove 23 and the second arc-shaped groove 24 matched with the protruding teeth 33 are arranged at intervals along the axial direction of the inner tool seat 20 , And the two are communicated through an axial slot 25, and the connecting rod 30 is movably connected to the inner cutter seat 20 in the axial direction, so that the protruding teeth 33 are connected between the first arc-shaped slot 23 and the inner cutter seat 20. When switching between the second arc-shaped grooves 24, when the protruding teeth 33 are located in the first arc-shaped groove 23, the connecting rod 30 can be located between the first angle interval and the second angle interval When the protruding teeth 33 are located in the second arc-shaped groove 24, the connecting rod 30 can only move within the first angle range; when the connecting rod 30 is in the first linear direction When moving relative to the inner tool seat 20, the protruding teeth 33 can be moved from the first arc-shaped groove 23 to the second arc-shaped groove 24, and the first linear direction is the feeding of the drill bit direction.

As shown in FIG. 4 , in a specific embodiment, the connecting rod 30 is provided with a main water channel 301 inside, and a first liquid separation chamber 103 is formed between the inner wall of the outer knife holder 10 and the outer wall of the connecting rod 30 . , a second liquid separation chamber 203 is formed between the end of the connecting rod 30 and the inner knife seat 20, and the side wall of the connecting rod 30 is provided with a first liquid separation chamber 103 and a second liquid separation chamber respectively connected The first through hole 34 and the second through hole 35 of 203; the outer knife holder 10 is provided with a first flow channel 101, and the liquid inlet of the first flow channel 101 is communicated with the first liquid separation chamber 103, so The liquid outlet of the first flow channel 101 is formed on the crown of the outer knife seat 10, and the liquid outlet is located between two adjacent outer knife wings 11; the inner knife seat 20 is provided with a second flow channel 201, the liquid inlet of the second flow channel 201 is communicated with the second liquid separation chamber 203, the liquid outlet of the second flow channel 201 is formed at the end of the inner knife seat 20, and the outlet The liquid port is located between two adjacent inner blades 21 .

As shown in FIGS. 4 and 20 , in a specific embodiment, a convex ring 36 is formed on the connecting rod 30 , and a first step portion 13 and a second step portion 14 are formed on the inner wall of the outer tool holder 10 , so The inner annular surface of the first stepped portion 13 is in contact with the outer wall of the connecting rod 30 , the inner annular surface of the second stepped portion 14 is spaced from the outer wall of the connecting rod 30 , and the first stepped portion 13 and the second step portion 14 is located on the side close to the crown of the outer tool holder 10 relative to the raised ring 36 , the raised ring 36 , the inner wall of the outer tool holder 10 , the first step portion 13 and the second step portion 14 The first liquid separation chamber 103 is formed together, and when the first liquid separation chamber 103 is filled with liquid, a thrust in a first linear direction can be generated on the outer knife seat 10 .

As shown in FIGS. 4 and 20 , in a specific embodiment, the liquid inlet of the first flow channel 101 is formed on the inner annular surface of the second step portion 14 .

As shown in FIGS. 8 , 12 and 19 , in a specific embodiment, a closing mechanism is provided between the connecting rod 30 and the inner knife holder 20 , and the closing mechanism is assembled so that when the connecting rod 30 is connected to When the inner knife seat 20 is at a first relative preset angle, the water channel between the main water channel 301 and the second liquid separation chamber 203 can be disconnected, and the first relative preset angle is located at the first relative preset angle. Within an angle interval, and when the connecting rod 30 and the inner tool holder 20 are at other relative angles within the first angle interval and the second angle interval, the main water channel 301 and the second liquid can be separated The water paths between the cavities 203 communicate.

As shown in FIGS. 8 , 12 and 19 , in a specific embodiment, the closing mechanism includes an axial groove 204 formed on the inner wall of the inner knife seat 20 . When the connecting rod 30 is connected to the inner knife When the seat 20 is at other relative angles other than the first relative preset angle within the first angle interval and the second angle interval, the second through hole 35 is opposite to the axial slot 204, and the second The through hole 35 communicates with the second liquid separation chamber 203 through the axial groove 204 ; when the connecting rod 30 and the inner knife seat 20 are at the first relative preset angle, the second The through hole 35 is staggered from the axial strip groove 204 , and at this time, the second through hole 35 is disconnected from the second liquid separation chamber 203 .

As shown in FIG. 1 , in a specific embodiment, a bar-shaped key 202 is formed on the inner blade holder 20 extending from the outer end of the inner blade wing 21 to the side wall of the inner blade holder 20 . The inner wall of the outer tool holder 10 is formed with a key slot which is matched with the bar key 202 .

As shown in FIG. 3 , in a specific embodiment, the number of the outer blades 11 is greater than the number of the inner blades 21 , and each inner blade 21 corresponds to a radially aligned blade with the outer blade 11 . The outer blade 11, the inner ends of these outer blades 11 aligned with the inner blade 21 are provided with auxiliary liquid jetting ports 102, the auxiliary liquid jetting ports 102 are arranged towards the outer wall of the bar key 202, the auxiliary liquid jetting The liquid port 102 communicates with the first flow channel 101 . The auxiliary liquid jetting port 102 can clean the surface of the bar key 202 to prevent sediment from hindering the relative movement between the inner tool holder 20 and the outer tool holder 10 .

The concrete working process and principle of the present invention are as follows:

Assuming that the initial state of the drill bit is station 1, as shown in Figure 1-8, when the drill bit is lowered into the well, it can directly cut the fluffy formation; when encountering tight formations, first stop feeding, and then follow the first direction. Rotate the drill rod in the opposite direction, so that the connecting rod 30 is rotated to the state shown in Figures 9-12, the connecting rod 30 and the inner cutter seat 20 are at the first relative preset angle, at this time, the main water channel 301 is disconnected from the second liquid separation chamber 203. Referring to Fig. 12, the water pressure all acts on the first liquid separation chamber 103, thereby generating a large thrust force on the outer tool holder 10, causing the outer tool holder 10 to move downward, and at the same time, the drill rod is pulled upward. At this time, since the outer tool holder 10 is not limited by the axial direction of the inner tool holder 20, the outer tool holder 10 will gradually move toward the crown of the inner tool holder 20 until the ends of the two are flush, and the connecting rod 30 During the upward pulling process, the protruding teeth 33 are moved from the second arc-shaped groove 24 to the first arc-shaped groove 23 at the same time. At this time, rotating the drill rod in the first direction can make the protruding teeth 33 snap into the first arc-shaped groove. 23, when the connecting rod 30 rotates relative to the inner tool seat 20 at the limit position, the ball 22 can be pushed into the annular groove 12, so as to realize the axial fixation of the outer tool seat 10 and the inner tool seat 20. At this time, the drill rod continues. Feeding down allows the outer cutting unit and the inner cutting unit to drill on the same section. When encountering the fluffy formation again, the drill rod rotates in the opposite direction in the first direction again, so that the connecting rod 30 and the inner cutter seat 20 are switched to the first angle range, and then the drill rod is driven to feed downward. At this time, the outer cutter seat 10 and the inner cutter seat 20 are blocked by the rock formation and therefore remain stationary, so that the connecting rod 30 moves downward relative to the inner cutter seat 20, the protruding teeth 33 move into the second arc groove 24 again, and finally drive the drill rod again. Rotate in the first direction while driving the drill rod to feed downward. At this time, since the protruding teeth 33 are located in the second arc-shaped groove 24, the connecting rod 30 and the inner tool seat 20 can be kept in the first angle range, so that the locking The mechanism remains in the unlocked state, the outer tool holder 10 loses the axial restriction of the inner tool holder 20 and is blocked by the rock layer until the inner tool holder 20 protrudes to the station 1 relative to the outer tool holder 10. At this time, the connecting rod 30 is on the The protruding ring 36 is in contact with the second step portion 14 on the inner side of the outer tool holder 10, thereby driving the outer tool holder 10 to feed downward again. Based on the above-mentioned principle, the present invention realizes the repeated adjustment of the drill bit between two stations, and does not require frequent replacement of the drill bit in a complex formation environment, thereby improving the drilling efficiency.

It should be noted that, since the present invention requires the drill rod to be able to drive the connecting rod 30 to rotate forward and reverse at the same time, a special connecting structure is adopted. Specifically, the connecting portion 31 includes the external thread 311 provided on the outer wall of the connecting rod 30 And the spline groove 312, the drill rod can realize synchronous forward and reverse rotation through the spline and the connecting rod 30, a nut block is arranged on the drill rod, and the nut block is threadedly connected with the external thread 311 to realize the shaft of the drill rod and the connecting rod 30. to tighten. In the present invention, the hardness of the rock formation can be judged by the feed pressure and feed speed of the drill pipe. For example, under the same pressure, the faster the feed speed is, the softer the rock formation is, and the slower the feed speed is, the harder the rock formation is. In addition, it is also possible to determine the properties of rock formations at different depths through preliminary exploration (such as ultrasonic detection), and then directly select the appropriate drill bit station according to the drilling depth.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

1. A PDC bit adapted for use in densifying mudstone formations, comprising:

the external cutting unit comprises an outer cutter holder (10), wherein a central hole penetrating through the outer cutter holder (10) is formed in the center of the outer cutter holder (10), outer cutter wings (11) are arranged on the crown portion of the outer cutter holder (10), the outer cutter wings (11) extend to the side face of the outer cutter holder (10) from the edge of the central hole, and a plurality of outer cutter wings (11) are arranged at intervals along the circumferential direction of the outer cutter holder (10);

the inner cutting unit comprises an inner cutter holder (20), inner blades (21) are arranged at the crown part of the inner cutter holder (20), the inner blades (21) are only distributed on the end surface of the inner cutter holder (20), and a plurality of inner blades (21) are arranged at intervals along the circumferential direction of the inner cutter holder (20); the inner cutter holder (20) is movably arranged in a central hole of the outer cutter holder (10) along the axial direction, so that the inner cutting unit and the outer cutting unit can be switched between the following two stations: the first station, the inner blade (21) axially protrudes for a preset distance relative to the outer blade (11); and a second station, wherein the inner blade (21) is flush with the crown of the outer blade (11); the inner cutter holder (20) is connected with the outer cutter holder (10) in a synchronous rotating manner along the circumferential direction;

the connecting rod (30) is provided with a connecting part (31) for connecting a drill rod at one end, and the other end of the connecting rod (30) is connected with the inner cutter holder (20) so as to drive the inner cutter holder (20) to feed along the axial direction and rotate along the circumferential direction;

the locking mechanism is arranged between the inner cutter holder (20) and the outer cutter holder (10), is assembled to be provided with a locking station and an unlocking station, and can keep the outer cutting unit and the inner cutting unit which are positioned at the second station in the second station when the locking mechanism is positioned at the locking station so that the outer cutting unit and the inner cutting unit can be synchronously fed in the state of the second station; when the locking mechanism is located at an unlocking station, the outer cutting unit can freely move relative to the inner cutting unit along the axial direction, so that when the inner cutting unit is fed, the outer cutting unit can be switched to the first station under the blockage of rock strata and is kept at the first station;

the outer blade (11) and the inner blade (21) are provided with diamond composite cutting teeth (40).

2. The PDC drill bit suitable for tight mudstone formations according to claim 1, wherein the inner cutter holder (20) is provided with a blind hole at one end far away from the inner blades (21), and the connecting rod (30) is inserted into the blind hole; the locking mechanism comprises a ball (22) movably arranged on the side wall of the inner cutter holder (20) and an annular groove (12) arranged on the inner wall of the outer cutter holder (10), when the inner cutting unit and the outer cutting unit are positioned at the second station, the ball (22) is aligned with the annular groove (12), a radial hole penetrating through the side wall is formed in the side wall of the inner cutter holder (20), the ball (22) is arranged in the radial hole along the radial movement of the inner cutter holder (20), the diameter of the ball (22) is greater than the thickness of the side wall of the inner cutter holder (20), a groove (32) is formed in the position, corresponding to the ball (22), of the connecting rod (30), the bottom surface of the groove (32) is in smooth transition with the outer wall of the connecting rod (30), and the connecting rod (30) is in running fit with the inner cutter holder (20) within a preset angle range, the connecting rod (30) and the inner tool apron (20) can be switched between a first angle interval and a second angle interval, when the connecting rod (30) and the inner tool apron (20) are located in the first angle interval, the ball (22) is opposite to the groove (32), the inner side of the ball (22) can be partially accommodated in the groove (32), so that the outer side of the ball (22) avoids the annular groove (12), and the locking mechanism is located at the unlocking station; when the connecting rod (30) and the inner tool apron (20) are located in a second angle interval, the groove (32) and the ball (22) are staggered with each other along the circumferential direction, so that the ball (22) is pushed into the annular groove (12) by the connecting rod (30), and the locking mechanism is located at the locking station; when the connecting rod (30) rotates relative to the inner tool apron (20) along a first direction, the two angle sections are switched from a first angle section to a second angle section, and the first direction is the cutting direction of the drill bit.

3. The PDC drill bit suitable for tight mudstone formations according to claim 2, wherein the connecting rod (30) is provided with convex teeth (33) on the outer wall thereof, the inner cutter holder (20) is provided with first arc-shaped slots (23) and second arc-shaped slots (24) on the inner wall thereof, the first arc-shaped slots (23) and the second arc-shaped slots (24) are axially spaced along the inner cutter holder (20) and are communicated with each other through an axial slot (25), the connecting rod (30) is axially movably connected with the inner cutter holder (20) so as to switch the convex teeth (33) between the first arc-shaped slots (23) and the second arc-shaped slots (24), and when the convex teeth (33) are located in the first arc-shaped slots (23), the connecting rod (30) is capable of moving between the first angle interval and the second angle interval, when the convex tooth (33) is positioned in the second arc-shaped groove (24), the connecting rod (30) can only move in the first angle interval; when the connecting rod (30) moves relative to the inner cutter holder (20) along a first linear direction, which is the feed direction of the drill, the convex tooth (33) can be moved from the first arc-shaped groove (23) to the second arc-shaped groove (24).

4. The PDC drill bit suitable for compact mudstone formations according to claim 3, wherein the connecting rod (30) is internally provided with a main water channel (301), a first liquid dividing cavity (103) is formed between the inner wall of the outer cutter holder (10) and the outer wall of the connecting rod (30), a second liquid dividing cavity (203) is formed between the end of the connecting rod (30) and the inner cutter holder (20), and a first through hole (34) and a second through hole (35) which are respectively communicated with the first liquid dividing cavity (103) and the second liquid dividing cavity (203) are formed in the side wall of the connecting rod (30); a first flow channel (101) is arranged in the outer cutter holder (10), a liquid inlet of the first flow channel (101) is communicated with the first liquid dividing cavity (103), a liquid outlet of the first flow channel (101) is formed in the crown of the outer cutter holder (10), and the liquid outlet is positioned between two adjacent outer blades (11); the inner cutter holder (20) is internally provided with a second runner (201), a liquid inlet of the second runner (201) is communicated with the second liquid dividing cavity (203), a liquid outlet of the second runner (201) is formed at the end part of the inner cutter holder (20), and the liquid outlet is positioned between two adjacent inner blades (21).

5. The PDC bit suitable for use in tight mudstone formations of claim 4, a convex ring (36) is formed on the connecting rod (30), a first step part (13) and a second step part (14) are formed on the inner wall of the outer cutter holder (10), the inner ring surface of the first step part (13) is attached to the outer wall of the connecting rod (30), the inner ring surface of the second step part (14) and the outer wall of the connecting rod (30) are arranged at intervals, the first step part (13) and the second step part (14) are positioned on one side close to the crown part of the outer tool apron (10) relative to the convex ring (36), the convex ring (36), the inner wall of the outer cutter holder (10), the first step part (13) and the second step part (14) jointly enclose to form the first liquid separation cavity (103), when the first liquid separation cavity (103) is filled with liquid, a thrust in a first linear direction can be generated on the outer cutter holder (10).

6. The PDC bit suitable for tight mudstone formations of claim 5 wherein the inlet of the first flow channel (101) is formed on an inner annular surface of the second step portion (14).

7. The PDC bit suitable for tight mudstone formations according to claim 6, wherein a closing mechanism is provided between the connecting rod (30) and the inner cutter holder (20), the closing mechanism being fitted to enable a water path between the main water path (301) and the second diversion chamber (203) to be disconnected when the connecting rod (30) and the inner cutter holder (20) are at a first relative preset angle, the first relative preset angle being within the first angular interval, and to enable a water path between the main water path (301) and the second diversion chamber (203) to be connected when the connecting rod (30) and the inner cutter holder (20) are at other relative angles within the first and second angular intervals.

8. The PDC drill bit suitable for tight mudstone formations according to claim 7, wherein the closing mechanism comprises an axial groove (204) formed in the inner wall of the inner tool holder (20), and when the connecting rod (30) and the inner tool holder (20) are at other relative angles except the first relative preset angle in the first angle interval and the second angle interval, the second through hole (35) is opposite to the axial groove (204), and the second through hole (35) is communicated with the second diversion cavity (203) through the axial groove (204); when the connecting rod (30) and the inner cutter holder (20) are at the first relative preset angle, the second through hole (35) and the axial strip groove (204) are staggered, and at the moment, the second through hole (35) is disconnected with the second liquid dividing cavity (203).

9. The PDC drill bit suitable for tight mudstone formations according to claim 8, wherein the inner cutter base (20) is formed with a bar key (202) extending from the outer end of the inner blade (21) to the side wall of the inner cutter base (20), and the inner wall of the outer cutter base (10) is formed with a key slot for cooperating with the bar key (202).

10. The PDC bit for a tight mudstone formation according to claim 9, characterized in that the number of the outer blades (11) is greater than that of the inner blades (21), each inner blade (21) has one outer blade (11) aligned radially therewith, the inner ends of the outer blades (11) aligned with the inner blades (21) are provided with auxiliary liquid injection ports (102), the auxiliary liquid injection ports (102) are arranged toward the outer wall of the bar-shaped key (202), and the auxiliary liquid injection ports (102) are communicated with the first flow channel (101).

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