SYSTEM AND METHOD FOR MONITORING WEAR OF A DRILL BIT

Abstract

The present disclosure relates to a system for monitoring wear of a drill bit, comprising: a drill bit provided with: a cutting surface; an internal matrix; and a channel at an internal region of the drill bit, beneath the cutting surface; a source of pressurised drilling fluid, the internal matrix of the drill bit being connected to the source of pressurised drilling fluid, and configured to receive drilling fluid from the internal matrix; and a monitor for monitoring the pressurised drilling fluid; wherein the channel is configured to release drilling fluid to an exterior of the drill bit when the cutting surface above the internal region is worn away to expose the channel. There is also provided a drill bit and method associated with the system.

Description

TECHNICAL FIELD

The present disclosure relates to drill bits for drilling oil wells. More particularly, the present disclosure relates to systems for detecting wear of oil well drilling bits.

BACKGROUND

An oil well is drilled in several steps. The steps can have different diameters. Each of these steps is known as a phase. The main standard configuration of oil well drilled in Brazil is as follows:

Phase 1: drilled with 36″ bit and cased with 30″ steel tubing;

Phase 2: drilled with 26″ bit and cased with 20″ steel tubing;

Phase 3: drilled with 17½″ bit and cased with 13⅜″ steel tubing;

Phase 4: drilled with 12¼″ bit and cased with 9⅝″ steel tubing;

Phase 5: drilled with 8½″ bit and cased with 7″ steel tubing.

Each of the phases listed above is drilled with one or more drill bits connected to the drill string (i.e. its lower end: Bottom Hole Assembly—BHA), which includes a set of tools and equipment performing measurements of the physical properties of the rocks drilled as well as mapping the path of the well.

The drilling rig transmits weight (WOB—weight on bit), rotation (RPM—revolutions per minute) and torque via the drill string to promote borehole drilling.

Drill bits are divided into two main groups: roller bits (or cone bits, three-cone bits being the most common) and fixed-cutter bits. The main difference between these two main groups is that the roller bits cut rock by a crushing mechanism, whereas the fixed-cutter bits cut rock by a shearing mechanism.

At present, three types of bits have been applied for drilling in oil wells: three-cone bits, impregnated bits and PDC (polycrystalline diamond compact) bits. The three-cone bits belong to the group of roller bits and the impregnated and PDC bits belong to the group of fixed-cutter bits.

The main limitation of the three-cone bits is on the number of hours of use. When the limitation is exceeded, there is an increase in the risk of loss of cone(s) from the bit and loss of rig time.

Impregnated bits possess fins into which small synthetic diamond particles are inserted. These particles can be of the order of hundredths of a millimetre (as also used for grinding wheels). This type of bit requires high rotary speeds, of about 1000 rpm. Impregnated bits have high durability, but for the most part the average rate of penetration does not exceed 2 m/h.

The PDC bits consist of fins or plates where synthetic diamond cutters of circular shape are fixed. The cutters normally have diameters of 13, 16 and 19 mm.

A conventional PDC bit may be divided into gauge (G), shoulder (S), nose (N) and cone (C), as commonly known to those in the art and illustrated in the profile shown in FIG. 1. In bits with ballistic profile and dome, there is also a neck between the shoulder and the nose.

A very common type of wear for PDC bits is a ring mark. This consists of the loss of one or more rows of synthetic diamond cutters, generating a ring-shaped furrow in the matrix of the PDC bit, as illustrated in FIG. 2. Examination of a database of drill bits by the inventors showed that the vast majority of PDC bits that display wear with a ring mark do so in the shoulder region of the bit.

It should be emphasized that ring-mark wear is one of the most common types in PDC bits for drilling oil wells. It mainly occurs when drilling hard and/or abrasive rocks. These include rocks such as the carbonates of the presalt layer and the sandstones of the Maastrichiano and Campaniano in Espírito Santo.

The main problem resulting from the severity of ring-mark wear is narrowing of the borehole. Without knowledge of the wear, drilling can be continued until, for example, seizing of the drill string occurs in the part with the stabilizers. This causes a loss of time for conditioning the section drilled with the worn bit. In addition, when the wear is pronounced, the ring mark weakens the rest of the PDC fins due to the reduction of mass. This may cause breakage of the bit and consequently the need for “fishing” out the broken pieces from the well. That involves interrupting the drilling operations for a considerable length of time.

In an attempt to mitigate the aforementioned problems, technologies have appeared on the market that measure wear by means of a system of electric circuits positioned inside the PDC bit. Document US20100139987A1, for example, discloses a drill bit comprising a wear detecting system formed by at least one electric circuit installed in the body of the bit. When wear occurs, variations or interruptions are detected in the circuits, accurately identifying the level of wear of the bit.

Although the system described in document US20100139987A1 addresses the problem of detecting and signalling wear, such a technique requires installation of an electrical system in the body of the bit dedicated exclusively to this purpose, comprising battery, control/signalling system, power module, etc. Besides greatly increasing the manufacturing costs, this technique is liable to faults and maintenance, since the constant vibration of the bit in operation may damage the electrical components and the circuits. Moreover, insertion of circuits in the body of the bit is a quite expensive and laborious task.

Thus, there is a need in the prior art for a drill bit for drilling oil wells comprising a means for detecting wear thereof at low cost, by utilizing the systems and components already existing in the drill bit or drill string.

SUMMARY

As will be described in more detail below, aspects of the present disclosure at least partially solve the problems of the prior art described above in a practical and efficient manner.

In one aspect, a system and a method are provided for monitoring wear of a drill bit capable of detecting the wear of the bit simply and efficiently without the need for a dedicated additional electrical system.

In a further aspect, a system and a method are provided for monitoring wear of a drill bit that only use systems already pre-existing in the drilling system consisting of the bit, string, rig and other equipment.

In order to at least partially achieve the aspects described above, according to a first aspect of the disclosure there is provided: a system for monitoring wear of a drill bit, comprising one or more of: a drill bit provided with: a cutting surface; an internal matrix; and a channel at an internal region of the drill bit, beneath the cutting surface; a source of pressurised drilling fluid, the internal matrix of the drill bit being connected to the source of pressurised drilling fluid, and configured to receive drilling fluid from the internal matrix; and a monitor for monitoring the pressurised drilling fluid; wherein the channel is configured to release drilling fluid to an exterior of the drill bit when the cutting surface above the internal region is worn away to expose the channel.

Optionally, the system further comprises one or more drilling fluid outlets for supplying drilling fluid from the internal matrix to the exterior of the drill bit.

Optionally, the channel is enclosed within the drill bit.

Optionally, the channel is positioned at a predetermined distance from the cutting surface, such that exposure thereof to the exterior occurs due to wear of the cutting surface greater than or equal to the predetermined distance.

Optionally, the monitor is a pressure monitor for measuring the pressure of the pressurised drilling fluid.

Optionally, the channel extends closest to the cutting surface beneath a shoulder or nose section of the drill bit.

Optionally, the channel comprises at least one branching point.

Optionally, the monitor is positioned remotely relative to the bit.

Optionally, the monitor comprises a sensor for automatic detection of variation of pressure.

According to a second aspect of the disclosure, there is provided a drill bit, comprising at least one of: a cutting surface; an internal matrix connectable to a source of pressurised drilling fluid; and a channel at an internal region of the bit, beneath the cutting surface, configured to receive drilling fluid from the internal matrix, the channel extending to an internal region of the bit; wherein the channel is configured to release drilling fluid to an exterior of the drill bit when the cutting surface above the internal region is worn away to expose the channel.

Optionally, the drill bit further comprises one or more drilling fluid outlets for supplying drilling fluid from the internal matrix to the exterior of the drill bit.

Optionally, the channel is enclosed within the drill bit.

Optionally, the channel is positioned at a predetermined distance from the cutting surface, such that exposure thereof to the exterior occurs due to wear of the cutting surface greater than or equal to the predetermined distance.

Optionally, the channel extends closest to the cutting surface beneath a shoulder or nose section of the drill bit.

Optionally, the channel comprises at least one branching point.

According to a third aspect of the disclosure, there is provided a method of monitoring wear of a drill bit, the method comprising one or more of the steps of: providing a drill bit with a channel configured to be exposed to the exterior of the drill bit by wear of the drill bit; monitoring the pressure of the pressurised drilling fluid; and detecting a change in the pressurised drilling fluid, indicative of exposure of the channel to the exterior.

Optionally, the method is applied to the system of any of the variations of the first aspect

Optionally, the drill bit is the drill bit of any of the variations of the second aspect.

Optionally, the step of detecting a change comprises detecting a drop in pressure of the pressurised drilling fluid, and further optionally comprises detecting a drop in pressure of the pressurised drilling fluid for a predetermined time interval.

Optionally, the method further comprising an additional step of emitting an audible and/or visual alarm when a drop in pressure of the pressurised drilling fluid, indicative of exposure of the channel to the exterior, is detected.

According to a fourth aspect of the disclosure there is also disclosed a system for monitoring wear of a drill bit, comprising (i) a bit provided with a cutting surface, which possesses (i-a) a plurality of cutters, and (i-b) an internal matrix, supplied with drilling fluid under pressure, wherein the drilling fluid is dispensed from the internal matrix to the exterior by means of at least one drilling fluid outlet, the system further comprising (ii) a means for monitoring the pressure of the drilling fluid and (iii) at least one fluidic communication channel between the internal matrix and an internal region of the bit positioned at a predetermined distance from the cutting surface, the at least one channel being configured for releasing drilling fluid by means of exposure thereof to the exterior owing to the wear of the cutting surface being greater than or equal to the predetermined distance.

According to a fifth aspect of the disclosure, there is also disclosed a method for monitoring wear of a drill bit, applied to the monitoring system of the fifth aspect, comprising the steps of (i) monitoring the pressure of the drilling fluid by a means for monitoring the pressure of the drilling fluid and (ii) detecting a drop in pressure of the fluid for a predetermined time interval, indicative of exposure of at least one channel to the exterior.

According to a sixth aspect of the disclosure there is also disclosed a system for monitoring wear of a drill bit, comprising: a bit (10) provided with: a cutting surface (12, 12s, 12n) that has a plurality of cutters (12c); and an internal matrix (14), supplied with drilling fluid under pressure, wherein the drilling fluid is dispensed from the internal matrix (14) to the exterior by means of at least one drilling fluid outlet (16); and a means for monitoring the pressure of the drilling fluid, characterized in that the bit (10) additionally comprises: at least one channel (18) for fluidic communication between the internal matrix (14) and an internal region of the bit positioned at a predetermined distance (d) from the cutting surface (12, 12s, 12n), the at least one channel (18) being configured for releasing drilling fluid by means of exposure thereof to the exterior due to wear of the cutting surface greater than or equal to the predetermined distance (d).

Optionally, the internal matrix (14) is in fluidic communication with the matrix of the drill string.

Optionally, the at least one channel (18) comprises at least one portion parallel to the cutting surface (12, 12s, 12n).

Optionally, the at least one channel (18) comprises at least one branching.

Optionally, the means for monitoring the pressure of the drilling fluid is positioned remotely relative to the bit (10).

Optionally, the means for monitoring the pressure of the drilling fluid comprises a sensor for automatic detection of variation of pressure.

According to a seventh aspect of the disclosure, there is also disclosed a method for monitoring wear of a drill bit, applied to the system for monitoring wear of a drill bit as defined in any one of the variations of the sixth aspect, characterized in that it comprises the steps of: monitoring the pressure of the drilling fluid by a means for monitoring the pressure of the drilling fluid; and detecting a drop in pressure of the fluid for a predetermined time interval, indicative of exposure of the at least one channel (18) to the exterior.

Optionally, the method comprises the additional step of emitting an audible and/or visual alarm when a drop in pressure of the drilling fluid is detected.

BRIEF DESCRIPTION OF THE FIGURES

The detailed description presented hereunder refers to the appended figures and their respective reference numbers.

FIG. 1 shows a schematic profile view of a bit of a PDC bit type, as encountered in the prior art.

FIG. 2 shows a schematic top view of a PDC bit comprising a ring-mark wear, as encountered in the prior art.

FIG. 3 shows a schematic sectional view of a bit comprising a system as disclosed herein.

DETAILED DESCRIPTION

Firstly, it is emphasized that the description given hereunder is based on a preferred embodiment. As will be obvious to a person skilled in the art, however, the invention is not limited to this particular embodiment.

FIG. 3 shows a schematic sectional view of a drill bit 10. The bit 10 forms part of a system for monitoring drill bit wear. In this figure, the bit 10 is provided with a cutting surface 12. The cutting surface 12 is subdivided into a cutting portion of the shoulder 12s and a cutting portion of the nose 12n. The cutting surface 12 has a plurality of cutters 12c. The bit 10 can be a PDC bit.

The bit 10 can comprise an internal matrix 14. The matrix 14 can be supplied with pressurised drilling fluid. The drilling fluid can be dispensed from the internal matrix 14 to the exterior of the bit 10 by means of at least one drilling fluid outlet 16. Usually, there are a plurality of drilling fluid outlets 16. The internal matrix 14 can be in fluidic communication with the matrix of the drill string (not shown). The drill string matrix can, in its turn, be in fluidic communication with a tank or source of drilling fluid 19 (shown schematically in FIG. 3). Such a tank or source of drilling fluid 19 can be located above the drill string, optionally in the rig. Thus, drilling fluid can be injected from the tank or source of drilling fluid 19 to the bit 10, passing through the drill string.

The present system can further comprise a monitor 20 (shown schematically in FIG. 3) for monitoring the pressurised drilling fluid. The monitor 20 is for detecting a change indicative of wear, as discussed in more detail below. As such, the monitor could be a flowmeter monitoring the flow of drilling fluid through the drill bit, or could be a pressure monitor monitoring the pressure of the drilling fluid. Changes in these, or other, characteristics of the drilling fluid can be indicative of a change (i.e. wear) in the drill bit. The following description presents an example using a pressure monitor, for ease of understanding, but the skilled reader will appreciate that alternative monitors or sensors could be used to the same effect.

The monitor 20 can be positioned remotely relative to the bit 10. Optionally, the monitor 20 for monitoring the pressure of the fluid is a pressure monitoring system already usually existing in drilling rigs. Thus, a pressure monitor 20 for monitoring the pressure of the drilling fluid of the present system may be any pressure monitoring or control system of the prior art.

The present system can further comprise at least one channel 18. Channel 18 is for fluidic communication between the internal matrix 14 and an internal region of the bit. That is, the channel 18 is provided at an internal region of the bit 10, beneath the original, unworn, cutting surface 12. Such a region may be positioned at a predetermined distance d from the original cutting surface 12. Optionally, there may be a plurality of such channels 18. Each of these channels 18 is configured for releasing drilling fluid when they are exposed. Such exposure to the exterior of the bit 10 can occur in the case of wear of the cutting surface 12. For example, wear greater than or equal to the predetermined distance d will remove the material of the drill bit 10 originally more outwards than the channel 18, thus exposing the channel 18 to the exterior of the drill bit 10.

In other words, each channel 18 is, before wear, a closed channel, in the sense that it does not communicate fluid to the exterior of the bit 10 (the channel 18 is open to the internal matrix 14, in order to receive drilling fluid therefrom). As such, the channel 18 is enclosed within drill bit 10. In normal conditions, before wear ruptures the wall of the channel 18 to release fluid to the exterior of the bit 10, the fluid within the channel will be static, or near static. This contrasts, for example with the fluid outlets 16 which are open channels, through which drilling fluid flows to the exterior of the bit 10 under normal conditions.

In any case, when there is sufficient wear, to the point of exposing at least one channel 18 to the exterior, drilling fluid will be released from the internal matrix 14 to the exterior by means of this channel 18.

Once at least one channel 18 has been exposed to the exterior, drilling fluid will begin to leak out. Consequently, changes in the characteristics of the drilling fluid will occur, such as a changes in flowrate of the fluid through the drill bit or a drop in pressure of the fluid. Considering the change in pressure, the change in pressure can be detected by the pressure monitor 20 for monitoring the pressure of the drilling fluid. For example, the pressure monitor 20 may include a sensor for automatic detection of variation of pressure.

The duration of any significant pressure drop (i.e. a pressure drop of a greater amount than a determined threshold, or below a predetermined absolute threshold) can be monitored by the pressure monitor 20. In one implementation, once said significant drop in pressure of the fluid is detected for a predetermined time interval, action may be prompted to consider if excessive wear has occurred. For example an alarm, optionally an audible and/or visual alarm, can be emitted to the operators to indicate the possibility of excessive wear of the bit. In these circumstances the operations are preferably halted for visual inspection of the bit, and if excessive wear is confirmed, it is replaced. In other implementations it may be desirable to automatically halt drilling if a significant pressure drop is detected for a predetermined amount out of time.

The at least one channel 18 can comprise at least one branching point, as illustrated on the right in FIG. 3. This may allow a larger area of the cutting surface 12 to be covered with one and the same channel 18.

Optionally, a single channel can surround, with respect to the rotation axis of the bit 10, the full extent of the cutting surface 12. In this aspect, a channel 18 in the form of a ring is formed below the cutting surface 12. The ring may have one or more fluid connections back to the internal matrix 14.

Optionally, the channel 18 is positioned close to the cutting surface only in the region of the shoulder and nose of the bit 10. In other words, the channel 18 may come closest to the cutting surface 12 beneath the shoulder or nose of the bit 10, as opposed to the gauge or cone sections. The shoulder and nose are regions that are more susceptible to ring-mark wear.

It should be emphasized that although only two examples of formats of channels 18 are illustrated in FIG. 3, the invention is not limited to the format thereof. Thus, any format or shape of channel falls within the scope of the present idea.

In addition, there is provided a method for monitoring wear of a drill bit. Such a method may be applied to the monitoring system described above. The method can comprise one or more of the steps of:

(i) providing a drill bit 10 with a channel configured to be exposed to the exterior of the drill bit 10 by wear of the drill bit 10—such a drill bit 10 may be one as described above;(ii) monitoring the pressurised drilling fluid; and(iii) detecting a change in the fluid, e.g. a change in pressure for a predetermined time interval, indicative of exposure of the at least one channel 18 to the exterior.

Optionally, the method comprises an additional step of emitting an alarm or alert, such as an audible and/or visual alarm, when a change in the drilling fluid is detected.

Thus, the present disclosure provides a system and a method for monitoring wear of a drill bit capable of detecting the wear of the bit simply and efficiently without needing an additional electrical system. Moreover, only ancillary systems already pre-existing in the drilling system are used in the present monitoring system, namely the bit, string, rig and other equipment. This means there is a low cost of implementation.

Numerous variations falling within the scope of protection of the present application are permitted. This reinforces the fact that the present disclosure is not limited to the particular configurations/embodiments described above.

Modifications of the above-described apparatuses and methods, combinations between different variations as practicable, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the spirit and scope of the claims.

Claims

1. System for monitoring wear of a drill bit, comprising: a drill bit provided with:a cutting surface;an internal matrix; anda channel at an internal region of the drill bit, beneath the cutting surface;a source of pressurised drilling fluid, the internal matrix of the drill bit being connected to the source of pressurised drilling fluid, and configured to receive drilling fluid from the internal matrix; anda monitor for monitoring the pressurised drilling fluid;wherein the channel is configured to release drilling fluid to an exterior of the drill bit when the cutting surface above the internal region is worn away to expose the channel.

2. System according to claim 1, further comprising one or more drilling fluid outlets for supplying drilling fluid from the internal matrix to the exterior of the drill bit.

3. System according to claim 12, wherein the channel is enclosed within the drill bit.

4. System according to claim 1, wherein the channel is positioned at a predetermined distance from the cutting surface, such that exposure thereof to the exterior occurs due to wear of the cutting surface greater than or equal to the predetermined distance.

5. System according to claim 1, wherein the monitor is a pressure monitor for measuring the pressure of the pressurised drilling fluid.

6. System according to claim 1, wherein the channel extends closest to the cutting surface beneath a shoulder or nose section of the drill bit.

7. System according to claim 1, wherein the channel comprises at least one branching point.

8. System according to claim 1, wherein the monitor is positioned remotely relative to the drill bit.

9. System according to claim 1, wherein the monitor comprises a sensor for automatic detection of variation of pressure.

10. A drill bit, comprising: a cutting surface;an internal matrix connectable to a source of pressurised drilling fluid; anda channel at an internal region of the drill bit, beneath the cutting surface, configured to receive drilling fluid from the internal matrix, the channel extending to an internal region of the drill bit;wherein the channel is configured to release drilling fluid to an exterior of the drill bit when the cutting surface above the internal region is worn away to expose the channel.

11. The drill bit according to claim 10, further comprising one or more drilling fluid outlets for supplying drilling fluid from the internal matrix to the exterior of the drill bit.

12. The drill bit according to claim 10, wherein the channel is enclosed within the drill bit.

13. The drill bit according to claim 10, wherein the channel is positioned at a predetermined distance from the cutting surface, such that exposure thereof to the exterior occurs due to wear of the cutting surface greater than or equal to the predetermined distance.

14. The drill bit according to claim 10, wherein the channel extends closest to the cutting surface beneath a shoulder or nose section of the drill bit.

15. The drill bit according to claim 10, wherein the channel comprises at least one branching point.

16. Method of monitoring wear of a drill bit, the method comprising the steps of: providing the drill bit with a channel configured to be exposed to the exterior of the drill bit by wear of the drill bit;monitoring pressurised drilling fluid; anddetecting a change in the pressurised drilling fluid, indicative of exposure of the channel to the exterior.

17. Method according to claim 16, wherein the method is applied to the system of claim 1.

18. Method according to claim 16, wherein the drill bit is the drill bit of claim 10.

19. Method according to claim 16, wherein the step of detecting a change comprises detecting a change in pressure of the pressurised drilling fluid, and optionally comprises detecting a drop in pressure of the pressurised drilling fluid for a predetermined time interval.

20. Method according to claim 16, further comprising an additional step of emitting an audible and/or visual alarm when the change in the pressurised drilling fluid, indicative of exposure of the channel to the exterior, is detected.