CN107386987A - Interior chip removal jet stream decompression drill bit - Google Patents

Abstract

The present invention provides an internal chip removal jet pressure-reducing drill bit, which includes a polycrystalline diamond compact PDC drill bit body, and the PDC bit body is provided with a pressure-reducing structure, a chip extraction structure and a main flow channel for transporting initial drilling fluid. The bottom end of the PDC drill bit is provided with a chip removal groove; the pressure relief structure communicates with the main flow channel and is set opposite to the main flow channel, and the chip removal structure communicates with the pressure reduction structure and the chip removal groove respectively , the decompression structure is used to reversely flush the initial drilling fluid passing through the main channel from the decompression structure to generate negative pressure, and the chip extraction structure is used to use the negative pressure to carry the rock-carrying drilling fluid The interior of the PDC drill bit body is sucked through the flutes. The internal debris-removal jet pressure-reducing drill bit provided by the present invention can accelerate the flow of rock-carrying drilling fluid, efficiently clean bottom cuttings and rock slag, improve drilling efficiency, and avoid the problems of bottom holding effect and repeated breaking of cuttings.

Description

Internal chip removal jet pressure-reducing drill bit

technical field

The invention relates to drilling tool technology, in particular to an internal chip removal jet pressure-reducing drill bit, which belongs to the technical field of drilling and oil and gas engineering.

Background technique

Accelerating the exploration and development of unconventional oil and gas and reducing the cost of exploration and development are of great strategic significance for promoting the industrialization of unconventional oil and gas in my country, realizing the "unconventional oil and gas revolution", and alleviating the contradiction between oil and gas supply and demand in my country.

Drilling rate is one of the main factors affecting the cost of unconventional oil and gas. In a typical oil and gas well, close to 50% of the cost is spent on mechanical drilling. According to research and practice in the United States, if the drilling efficiency is doubled, the total drilling cost can be reduced by about 25%. Therefore, increasing the ROP is the primary pursuit of reducing drilling costs and maximizing benefits.

Reducing the bottom hole pressure and realizing local reverse circulation at the bottom hole can effectively increase the ROP. On the one hand, reducing the bottom hole pressure difference will reduce the plasticity of the rock to be broken at the bottom hole, and make the bottom hole rock change from plastic to brittle, thereby reducing the crushing strength. , improve the crushing efficiency; on the other hand, the local reverse circulation at the bottom of the well will reduce or eliminate the holding effect of the cuttings at the bottom of the well, and promote the newly generated cuttings to break away from the rock matrix at the bottom of the well in time to avoid repeated crushing.

Contents of the invention

In view of the above defects, the present invention provides an internal chip removal jet pressure-reducing drill bit, which is used to improve drilling efficiency.

The present invention provides an internal chip removal jet pressure-reducing drill bit, which includes: a polycrystalline diamond compact PDC drill bit body, the PDC bit body is provided with a pressure-reducing structure, a chip extraction structure and a main flow channel for transporting initial drilling fluid. The bottom of the PDC drill bit is provided with a chip removal groove;

The decompression structure communicates with the main channel and is opposite to the main channel, and the chip removal structure communicates with the decompression structure and the chip removal groove respectively, and the decompression structure is used to make the The initial drilling fluid in the main channel is reversely flushed from the decompression structure to generate negative pressure, and the chip removal structure is used to use the negative pressure to suck the rock-carrying drilling fluid into the PDC through the chip removal groove inside the drill body.

The internal chip removal jet depressurization drill bit as described above, wherein the depressurization structure includes a reverse high-speed jet nozzle and a negative negative nozzle that communicates with the outlet of the reverse high-velocity jet nozzle and extends along the opposite direction of the main channel. pressure delivery channel;

The inlet of the reverse high-speed jet nozzle communicates with the main channel.

The internal chip removal jet pressure-reducing drill bit as described above, wherein the angle between the axis of the reverse high-speed jet nozzle and the axis of the main flow channel is β, and 0°≤β<90°.

As mentioned above, the internal chip removal jet pressure-reducing drill bit, wherein, the chip removal structure includes an initial drilling fluid forward jet nozzle and a cuttings suction pipe;

The inlet of the initial drilling fluid forward jet nozzle communicates with the bottom end of the main channel, the outlet of the initial drilling fluid forward jet nozzle is arranged at the near end of the chip removal groove, and the cuttings suction pipe The inlet is arranged at the far end of the chip removal flute, and the outlet of the cuttings suction pipe communicates with the negative pressure conveying channel.

In the internal chip removal jet depressurization drill bit described above, there is an included angle between the axis of the initial drilling fluid forward jet nozzle and the axis of the main flow channel.

The above-mentioned internal chip removal jet pressure-reducing drill bit, wherein, the negative pressure delivery channel includes a negative pressure chamber, a throat pipe and a bypass pipe connected in sequence from the bottom end to the top end,

The first inlet of the negative pressure chamber communicates with the outlet of the reverse high-speed jet nozzle;

The second inlet of the negative pressure chamber communicates with the outlet of the cuttings suction pipe.

The internal chip removal jet pressure-reducing drill bit described above, wherein the bypass pipe is a pipe with two ports of unequal diameter, wherein the large-diameter port is the outlet of the bypass pipe, and the small-diameter port is the bypass port. entrance of the tube.

The internal chip removal jet depressurization drill bit as described above, wherein, the outlet of the bypass pipe communicates with the annular space formed between the drill pipe and the well wall.

In the internal chip removal jet pressure-reducing drill bit described above, a plurality of PDC blades are arranged at intervals along the circumferential direction at the bottom end of the PDC drill body, and the chip removal grooves are arranged between the plurality of PDC blades.

The internal chip removal jet pressure-reducing drill bit described above, wherein, the outside of the bottom end of the PDC drill body is provided with a gauge.

Implementation of the present invention has at least the following advantages:

1. The internal hydraulic structure and flow channel structure of the internal chip removal jet pressure-reducing drill bit provided by the present invention are relatively simple and easy to produce and process;

2. The internal debris removal jet pressure-reducing drill bit provided by the present invention can accelerate the flow of rock-carrying drilling fluid, efficiently clean bottom cuttings and rock slag, improve drilling efficiency, and avoid bottom-hole holding effect and repeated crushing of cuttings question;

3. The cuttings extraction structure is based on the principle of the sand pump to suck the bottom hole cuttings and fluid, and the bottom hole cuttings and fluid return from the inside of the drill bit to realize the reverse circulation at the bottom of the hole and reduce the holding effect;

4. The decompression structure is based on the principle of the jet pump, which reduces the pressure difference at the bottom of the well, realizes under-balance and improves the ROP;

5. The 360° gauge bit can form a smooth wellbore, which can effectively reduce the support pressure of horizontal wells.

Description of drawings

Fig. 1 is a sectional view of the internal chip removal jet pressure-reducing drill bit of the present invention;

Fig. 2 is the right side view of Fig. 1 .

Explanation of reference signs:

1: PDC drill body;

101: main channel;

102: flutes;

103: gauge;

104: PDC blade;

201: reverse high-speed jet nozzle;

202: Negative pressure delivery channel;

202a: negative pressure chamber;

202b: throat;

202c: bypass pipe;

301: initial drilling fluid forward jet nozzle;

302: cuttings suction pipe;

A: The first entrance;

B: Second entrance.

detailed description

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, and Not all examples. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

It should be noted that, in the present invention, the azimuth "top" refers to the position close to one end of the drill pipe, the azimuth "bottom" refers to the position near the end of the drill bit, and the azimuth "near end" refers to the position near the end surface of the drill bit. The position near the end of the drill bit central axis in the radial direction, the azimuth "distal end" refers to the position away from the end of the drill bit central axis in the radial direction of the bottom end face of the drill bit, and the direction "positive" refers to the position where the initial drilling fluid enters Direction, direction "Reverse" refers to the direction that changes the initial drilling fluid entry direction by 90°-180°.

In addition, in the present invention, the initial drilling fluid refers to the drilling fluid pumped from the mud pump to the drill pipe without cuttings and slag; the rock-carrying drilling fluid refers to the drilling fluid passing through the bottom working face, Drilling fluid carrying cuttings and slag.

Fig. 1 is a cross-sectional view of the internal chip removal jet pressure-reducing drill bit of the present invention, and Fig. 2 is a right view of Fig. 1 .

Please refer to Fig. 1-Fig. 2, the internal chip removal jet pressure-reducing drill bit of the present embodiment includes: a polycrystalline diamond compact PDC bit body 1, and the PDC bit body 1 is provided with a pressure-reducing structure, a chip extraction structure and an initial drilling fluid delivery The main channel 101 of the main body 1 of the PDC bit is provided with chip removal grooves 102; The depressurization structure is used to make the initial drilling fluid through the main channel 101 reversely flushed from the decompression structure to generate negative pressure, and the chip extraction structure is used to use negative pressure to suck the rock-carrying drilling fluid into the PDC bit body 1 through the chip removal groove 102 internal.

The inside of the PDC bit main body 1 in this embodiment is provided with a main channel 101 for the initial drilling fluid to enter the PDC bit main body 1. It is conceivable that the top of the PDC bit main body 1 is connected with a drill pipe (not shown), and The inlet of the main channel 101 is connected with the liquid outlet of the drill pipe, so that the initial drilling fluid in the drill pipe enters the main channel 101 through the inlet of the main channel 101 .

Specifically, the main body 1 of the PDC drill bit in this embodiment is fixedly connected with the drill rod during use, and may be fixedly connected by threads. The internal chip-removal jet pressure-reducing drill bit of this embodiment can be that the PDC drill bit main body 1 is provided with an internal thread, which cooperates with the external thread provided by the drill rod to realize a fixed connection; or, the PDC drill bit main body 1 is provided with an external thread, and the drill rod is provided with The internal thread fits to achieve a fixed connection. Of course, the PDC bit main body 1 and the drill pipe can also be fixedly connected by welding or other connection methods, which is not specifically limited in the present invention.

In this embodiment, the cross section of the main channel 101 may be circular, elliptical, polygonal, or irregular. In order to reduce the resistance of the main channel 101 to the initial drilling fluid and increase the cleaning power of the initial drilling fluid to the bottom of the well, the main part of the main channel 101 in this embodiment is preferably a circular channel, and the bottom of the main channel 101 is preferably a trapezoidal channel. Simultaneously, the main flow channel 101 can be a separate pipeline, and can also form the above-mentioned main flow channel 101 by opening a through hole on a columnar part inside the PDC bit main body 1. Of course, other structural forms can also be used, and the present invention does not make Specific restrictions.

Continuing to refer to Fig. 1-Fig. 2, the bottom end surface of the PDC bit body 1 is also provided with chip removal groove 102, and this chip removal groove 102 can accommodate the rock-carrying drilling fluid produced after drilling, before the rock-carrying drilling fluid enters the PDC The inside of the drill body 1 provides a path that is convenient to be sucked into the inside of the PDC drill body 1 before the reverse circulation is realized. The end faces are evenly distributed in the circumferential direction, and can also be irregularly distributed in any direction. Those skilled in the art can set them according to the specific conditions of drilling and the specific conditions of the bottom end face of the PDC bit main body 1, and the present invention does not make specific limitations.

In this embodiment, the depressurization structure is specifically arranged inside the PDC bit body 1, and the depressurization structure communicates with the main channel 101 and is set in reverse, so that the initial drilling fluid in the main channel 101 can be used to generate negative pressure, and the negative pressure The effect on the bottomhole fluid and cuttings reduces the local pressure at the bottom of the well, reduces the pressure difference at the bottom of the well, promotes the cuttings to leave the bottom of the well and accelerates the upward return, realizes local underbalance and improves the ROP. The present invention does not limit the specific expression form of the pressure reducing structure.

In this embodiment, the cuttings extraction structure is specifically arranged inside the PDC bit main body 1. The cuttings extraction structure can use the initial drilling fluid in the main flow channel 101 to clean the bottom hole cuttings and fluid, and can also be used in the pressure reduction structure. The negative pressure helps the rock-carrying drilling fluid at the bottom of the well to enter the interior of the PDC bit main body 1 through the chip removal groove 102 to realize reverse circulation and reduce the holding effect. The present invention does not limit the specific structure of the chip extraction structure, as long as the above functions can be realized.

The pressure-reducing structure and the chip removal structure in this embodiment can be set according to the specific structure inside the PDC drill body 1, and the present invention does not limit the specific number of the pressure-reducing structure and the chip removal structure, which can be one or more, specifically The number can be set according to the specific conditions of the internal chip removal jet pressure-reducing drill bit of the present invention when drilling.

In addition, a 360° diameter gauge 103 can also be provided outside the bottom end of the PDC bit body 1, so that the PDC bit body 1 can be strongly protected by the gauge 103, and the wellbore can be smoothed to effectively reduce the backpressure of the horizontal well. It is worth noting that, in the internal chip removal jet pressure-reducing drill bit of the present invention, no chip removal groove is provided on the gage.

The internal chip removal jet pressure-reducing drill bit provided in this embodiment has a simple structure and is easy to produce and process. Through the main channel 101 of the PDC bit body 1, the initial drilling fluid enters the interior of the PDC bit body 1 and cleans the PDC bit body 1 for drilling through the chip removal structure. For the generated cuttings and rock slag, the decompression structure utilizes the initial drilling fluid inside the drill bit to generate negative pressure, and the cuttings extraction structure uses negative pressure to suck the cuttings, rock slag, and drilling fluid at the bottom of the well through the chip removal groove 102 into the drill bit, thereby Complete the reverse circulation of drilling fluid, the present invention can accelerate the flow of rock-carrying drilling fluid, efficiently clean bottom cuttings and rock slag, improve drilling efficiency, avoid the problems of bottom-hole compression effect and repeated crushing of cuttings, and also It can reduce the holding effect and prevent leakage.

On the basis of the above-mentioned embodiments, the decompression structure in the internal chip removal jet decompression drill bit of the present embodiment includes a reverse high-speed jet nozzle 201 and communicates with the outlet of the reverse high-speed jet nozzle 201, and along the reverse direction of the main channel 101 The negative pressure conveying channel 202 extending in the direction; the inlet of the reverse high-speed jet nozzle 201 communicates with the main flow channel 101 .

Specifically, the inlet of the reverse high-speed jet nozzle 201 communicates with the main channel 101, and the outlet of the reverse high-speed jet nozzle 201 communicates with the inlet of the negative pressure delivery channel 202, so that the initial drilling fluid that enters the main channel 101 can be diverted to make part of the main channel The initial drilling fluid in 101 enters the reverse high-speed jet nozzle 201 through the inlet of the reverse high-speed jet nozzle 201 , and then enters the negative pressure delivery channel 202 from the exit of the reverse high-speed jet nozzle 201 . The reverse high-speed jet nozzle 201 in this embodiment refers to a nozzle that can change the inflow direction of the initial drilling fluid by 90°-180°. The inlet is sprayed to the top of the PDC bit body 1 in a direction opposite to the initial drilling fluid flow direction, so that negative pressure is generated at the inlet of the negative pressure delivery channel 202 . Under the action of the negative pressure, the rock-carrying drilling fluid at the bottom of the well will enter the interior of the PDC bit main body 1 through the chip removal structure through the chip removal groove 102, and then enter the negative pressure delivery channel 202 through the entrance of the negative pressure delivery channel 202, and pass through the negative pressure delivery channel 202. The outlet of the pressure delivery channel 202 is discharged from the PDC bit body 1 to realize the reverse circulation of the drilling fluid.

The position of the specific communication between the reverse high-speed jet nozzle 201 and the main channel 101 can determine the size of the negative pressure at the bottom of the well. The greater the negative pressure generated at the bottom. In FIG. 1 , the position where the reverse high-speed jet nozzle 201 communicates with the main channel 101 is close to the bottom of the main channel 101 , and the staff can set the specific communication position according to different drilling conditions.

In addition, this embodiment does not limit the axial section of the negative pressure delivery channel 202, which can be a regular or irregular structure. In order to facilitate the discharge of rock-carrying drilling fluid, the axial section of the negative pressure delivery channel 202 in this embodiment It is an irregular structure, that is, a horn-shaped structure with a thin bottom and a thick top.

The present embodiment does not specifically limit the number of the reverse high-speed jet nozzle 201 and the negative pressure delivery channel 202, it can be one or more, but the number of the reverse high-speed jet nozzle 201 and the negative pressure delivery channel 202 must be One to one correspondence.

Of course, in order to facilitate the drilling and development of oil and gas wells in various situations, the negative pressure generated by the pressure-reducing structure can also be adjusted according to the axis of the reverse high-speed jet nozzle 201 and the main channel. The angle β between the axes of 101 is adjusted, wherein, 0°≤β<90°, when β is smaller, the negative pressure generated is greater, and the power to promote cuttings to leave the bottom of the well and accelerate upward return is greater.

Further, the chip extraction structure in the internal chip removal jet pressure-reducing drill bit of this embodiment includes the initial drilling fluid forward jet nozzle 301 and cuttings suction pipe 302; the inlet of the initial drilling fluid forward jet nozzle 301 and the main flow channel 101 The bottom end is connected, the outlet of the initial drilling fluid forward jet nozzle 301 is arranged at the near end of the chip removal flute 102, the inlet of the cuttings suction pipe 302 is arranged at the far end of the chip removal flute 102, and the outlet of the cuttings suction pipe 102 is connected to the negative The pressure delivery channel 202 communicates.

Specifically, the inlet of the initial drilling fluid forward jet nozzle 301 communicates with the bottom end of the main channel 101, and the outlet 301 of the initial drilling fluid forward jet nozzle 301 is arranged at the near end of the chip flute 102, so that the initial drilling fluid in the main channel 101 After being partly diverted by the reverse high-speed jet nozzle 201 of the negative pressure part, the remaining initial drilling fluid will enter the initial drilling fluid forward jet nozzle 301 through the entrance of the initial drilling fluid forward jet nozzle 301, and then the initial drilling fluid forward The outlet of the jet nozzle 301 sprays out the PDC bit main body 1, thereby stirring and cleaning the cuttings at the bottom of the well.

In addition, the cuttings suction pipe 302 is the only passage for the rock-carrying drilling fluid at the bottom of the well to enter the interior of the PDC bit body 1 from the chip removal groove 102. Specifically, the inlet of the cuttings suction pipe 302 is arranged at the far end of the chip removal groove 102, The outlet of the cuttings suction pipe 302 communicates with the negative pressure delivery channel 202 . Since the outlet of the cuttings suction pipe 302 is in communication with the negative pressure conveying channel 202, there is negative pressure at the outlet of the cuttings suction pipe 302, so that the rock-carrying drilling fluid at the bottom of the well will be drawn into the cuttings suction pipe 302 by the cuttings suction pipe 302. The entrance of the cuttings suction pipe 302 is sucked into the inside of the PDC bit main body 1, that is, it enters the cuttings suction pipe 302 through the entrance of the cuttings suction pipe 302, and then enters the negative pressure conveying channel 202 from the outlet of the cuttings suction pipe 302, and is finally drawn by the negative pressure conveying channel 202. The main body 1 of the PDC drill bit is discharged to complete the reverse circulation of the drilling fluid.

In order to maximize the use of the negative pressure generated by the decompression structure, the outlet of the cuttings suction pipe 302 can communicate with the inlet of the negative pressure delivery channel 202 (ie the outlet of the reverse high-speed jet nozzle 201 ).

The cross section of the cuttings suction pipe 302 may be circular, elliptical, polygonal, or irregular. In order to reduce the resistance of the cuttings suction pipe 302 to the rock-carrying drilling fluid and make the rock-carrying drilling fluid unimpeded, the cuttings suction pipe 302 in this embodiment is preferably a trumpet tube with a large inlet and a small outlet.

In this embodiment, the number of initial drilling fluid forward jet nozzle 301 and cuttings suction pipe 302 is not specifically limited, and may be one or more. The initial drilling fluid forward jet nozzle 301 and cuttings suction pipe 302 are both The numbers do not need to be in one-to-one correspondence, but the number of cuttings suction pipes 302 and the number of negative pressure delivery channels 202 must be in one-to-one correspondence.

In order to improve the efficiency of rock cleaning at the bottom of the hole and enable the cuttings suction pipe 302 to realize the efficient suction of the rock-carrying drilling fluid at the bottom of the hole, the axis of the initial drilling fluid forward jet nozzle 301 and the axis of the main flow channel 101 can have an included angle θ , and 0°≤θ<90°, so that the combined action of the initial drilling fluid forward jet nozzle 301 and the rotation of the PDC bit main body 1 generates a turbulent flow field at the bottom of the well, improving the force condition of the drilling fluid carrying rock at the bottom of the well.

In this embodiment, the negative pressure delivery channel 202 includes a negative pressure chamber 202a, a throat pipe 202b and a bypass pipe 202c connected in sequence from the bottom end to the top end, the first inlet A of the negative pressure chamber 202a and the reverse high-speed jet nozzle The outlet of 201 is communicated; the second inlet B of the negative pressure chamber of 202a is communicated with the outlet of cuttings suction pipe 302 .

The negative pressure delivery channel 202 can be refined so that it specifically includes a negative pressure chamber 202a, a throat pipe 202b, and a bypass pipe 202c from the bottom end to the top end, and the negative pressure chamber 202a communicates with the throat pipe 202b, and the throat pipe 202b communicates with the throat pipe 202b. The bypass pipe 202c communicates. Wherein, the negative pressure chamber 202a includes two inlets, respectively the first inlet A and the second inlet B, and the first inlet A communicates with the outlet of the reverse high-speed jet nozzle 201, and is used for using the reverse high-speed jet nozzle 201 to spray The initial drilling fluid generates negative pressure; the second inlet B communicates with the outlet of the cuttings suction pipe 302, and is used to use the pressure of the negative pressure chamber 202a to suck the rock-carrying drilling fluid into the negative pressure chamber 202a through the cuttings suction pipe 302, and then pass The throat pipe 202b and the bypass pipe 202c discharge the PDC bit main body 1 to complete the reverse circulation of the drilling fluid.

Further, in order to reduce the power of the rock-carrying drilling fluid ejected from the negative pressure chamber 202a, the bypass pipe 202c can be set as a pipe with two ports of different diameters, wherein the large-diameter port is the outlet of the bypass pipe 202c, and the small-diameter port is the outlet of the bypass pipe 202c. The port is the inlet of the bypass pipe 202c.

Specifically, the small-diameter port communicates with the outlet of the throat pipe 202b, and the large-diameter port communicates with the annular space (not shown) formed between the drill pipe and the well wall. When the rock-carrying drilling fluid is under the action of negative pressure, Enter the cuttings suction pipe 302 through the entrance of the cuttings suction pipe 302, and then spray out from the outlet of the cuttings suction pipe 302 and enter the negative pressure chamber 202a through the second entrance, and then flow into the negative pressure chamber 202a, where it will be injected by the reverse high-speed jet nozzle 201. Part of the initial drilling fluid released forms a high-speed jet, which passes through the negative pressure chamber 202a, the throat pipe 202b, and the bypass pipe 202c in sequence from the bottom to the top, and finally enters the annulus. When traveling to the bypass pipe 202c, due to its special structure with a small inlet and a large outlet, the high-speed jet will decelerate in the bypass pipe 202c.

Referring to FIG. 2 , the bottom end of the PDC drill body 1 in this embodiment is provided with a plurality of PDC blades 104 at intervals along the circumferential direction, and chip removal grooves are arranged between the plurality of PDC blades 104 . Specifically, the PDC blade 104 is a working part of the chip removal jet depressurization drill bit of the present invention for cutting rock, and several PDC cutting teeth (not shown) are distributed on its surface. In order to clean the cuttings and debris cut off by each PDC blade 104 in time, and keep the balance of the PDC bit body 1 , chip removal flutes 102 can be arranged between multiple PDC blades 104 . In addition, the present invention does not limit the specific number of PDC blades 104 , there are 5 PDC blades in FIG. 2 .

The specific working process of the internal chip removal jet pressure-reducing drill bit of the above-mentioned embodiment is as follows:

During the drilling process, the internal debris removal jet depressurizes the drill bit to rotate, so that the PDC cutting teeth on the PDC blade 104 cut rocks to generate cuttings. At the same time, the high-pressure initial drilling fluid enters the main channel 101 by the drill pipe, and a part of the high-pressure initial drilling fluid is ejected from the reverse high-speed jet nozzle 201 to form a high-speed jet. The high-speed jet generates negative pressure in the negative pressure chamber 202a, and the negative pressure in the negative pressure chamber 202a The fluid and cuttings at the bottom of the well are sucked through the cuttings suction pipe 302, thereby reducing the pressure difference at the bottom of the well, reducing the holding effect of cuttings, creating an underbalanced condition at the bottom of the well, and increasing the ROP. Another part of the high-pressure initial drilling fluid enters the initial drilling fluid forward jet nozzle 301 of the cuttings extraction structure, and is ejected with a high-speed jet. The high-concentration turbulence enables the cuttings suction pipe 302 to efficiently suck the bottom hole cuttings and bottom hole drilling fluid in the chip removal flute 102 . Bottomhole cuttings and bottomhole drilling fluid enter the negative pressure chamber 202a through the cuttings suction pipe 302 under the suction effect of the reverse high-speed jet nozzle 201 .

The reverse high-speed jet nozzle 201 of the pressure-reducing structure ejects a high-speed jet, which generates negative pressure to entrain cuttings in the negative pressure chamber 202a, and the bottomhole cuttings and bottomhole drilling fluid are brought into The high-speed jet is discharged into the annular space after the speed of the high-speed jet decreases in the bypass pipe 202c.

The internal water conservancy structure and flow channel of the internal chip removal jet pressure-reducing drill bit of the present invention are relatively simple, and are easy to produce and process. The fluid is returned from the inside of the drill bit to realize reverse circulation at the bottom of the well and reduce the holding effect; the pressure-reducing structure is based on the principle of the jet pump to reduce the bottom-hole pressure difference and achieve under-balance to increase the ROP.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. A chip removal jet pressure-reducing drill bit, it is characterized in that, comprising: polycrystalline diamond compact PDC drill bit main body, described PDC drill bit main body inside is provided with the main channel of pressure-reducing structure, chip extraction structure and conveying initial drilling fluid , the bottom end of the PDC drill bit is provided with chip removal grooves; The decompression structure communicates with the main channel and is opposite to the main channel, and the chip removal structure communicates with the decompression structure and the chip removal groove respectively, and the decompression structure is used to make the The initial drilling fluid in the main channel is reversely flushed from the decompression structure to generate negative pressure, and the chip removal structure is used to use the negative pressure to suck the rock-carrying drilling fluid into the PDC through the chip removal groove inside the drill body. 2. The internal chip removal jet pressure-reducing drill bit according to claim 1, wherein the pressure-reducing structure includes a reverse high-speed jet nozzle and communicates with the outlet of the reverse high-speed jet nozzle, and along the main flow The negative pressure conveying channel extending in the opposite direction of the channel; The inlet of the reverse high-speed jet nozzle communicates with the main channel. 3. The internal chip removal jet pressure-reducing drill bit according to claim 2, characterized in that, the angle between the axis of the reverse high-speed jet nozzle and the axis of the main channel is β, 0°≤β< 90°. 4. The internal chip removal jet pressure-reducing drill bit according to claim 3, wherein the chip extraction structure includes an initial drilling fluid forward jet nozzle and a cuttings suction pipe; The inlet of the initial drilling fluid forward jet nozzle communicates with the bottom end of the main channel, the outlet of the initial drilling fluid forward jet nozzle is arranged at the near end of the chip removal groove, and the cuttings suction pipe The inlet is arranged at the far end of the chip removal flute, and the outlet of the cuttings suction pipe communicates with the negative pressure conveying channel. 5. The internal chip removal jet pressure reducing drill bit according to claim 4, characterized in that there is an included angle between the axis of the initial drilling fluid forward jet nozzle and the axis of the main channel. 6. The internal chip removal jet pressure-reducing drill bit according to claim 5, characterized in that, the negative pressure delivery channel includes a negative pressure chamber, a throat pipe and a bypass pipe connected in sequence from the bottom end to the top end, The first inlet of the negative pressure chamber communicates with the outlet of the reverse high-speed jet nozzle; The second inlet of the negative pressure chamber communicates with the outlet of the cuttings suction pipe. 7. The internal chip removal jet pressure-reducing drill bit according to claim 6, characterized in that, the bypass pipe is a pipe with two ports of unequal diameter, wherein the large-diameter port is the outlet of the bypass pipe, and the small diameter port is the outlet of the bypass pipe. The bore port is the inlet of the bypass pipe. 8 . The internal chip removal jet pressure reducing drill bit according to claim 7 , wherein the outlet of the bypass pipe communicates with the annular space formed between the drill pipe and the well wall. 9. The internal chip removal jet pressure-reducing drill according to any one of claims 1-8, characterized in that, the bottom end of the PDC drill body is provided with a plurality of PDC blades at intervals along the circumferential direction, and the chip removal groove is set between the plurality of PDC blades. 10. The internal chip removal jet pressure-reducing drill bit according to claim 9, characterized in that a gauge is provided outside the bottom end of the PDC drill body.