The invention is related to a drill bit with means for removing cuttings from the cutting structure of the drill bit.

N03 121 10 regards an autonomous device for subsurface investigations or investigation of ice, particularly to be appl ied when exploring for hydrocarbon or mineral occurrences. By applying weight on bit, and rotating a drill bit, the device which, in a most simplified embodiment comprise a drill bit, a bit driving motor, a control and measuring unit, a cable magazine, and possibly a cable output feeder, is arranged to work itself downwards into the earth's crust, concurrently feeding out cable and forming a connection to the earth's surface. The mass liberated and ground up by the drill bit is led past the device, possibly via a through-going channel/tube in the drilling device, to the bore hole behind/above the device and fills the bore hole at the same time as it forms a fixation for the cable connection fed out to the earth's surface.

This device raises a number of challenges, including drilling with little or no in-situ fluid available, and completely without external drilling fluid, to transport drilled cuttings away from the drill bit. This can lead to severe accumulation of drilled cuttings in and around the drill bit (bit balling), eventually making it impossible to cut formation and continue forward.

Another challenge is controlling maximum size of any particles generated by the drilling process, to prevent plugging or bridging of subsequent systems.

Problems with accumulation of cuttings at and near the drill bit may also be experienced with other drilling systems. In this document, the drill bit is described related to drilling in the earth's crust, ie. underground formations, mainly for exploring for hydrocarbons or minerals, but the invention is not limited to this use. GB 2496907 describes a drilling system which collects and store cuttings from drill ing. The system comprises a screw which transports the cuttings to a storage basket.

The object of the invention is to transport the drilled cuttings away from the face of the drill bit, while also possibly limiting the upper size of its particles, using mechanical means rather than fluids.

The object of the invention is achieved by means of the features of the patent claims.

In one embodiment, a drill bit comprises a cutter structure, at least one opening in the drill bit for removal of cuttings from the cutter structure, and at least two transport screws arranged in connection to the opening for transporting cuttings into the opening and further to a location remote from the drill bit.

The drill bit may be any kind of drill bit for drilling into a structure by breaking apart, cutting or crushing rock formations when drilling a wellbore, such as those drilled to extract water, gas, or oil. Examples of drill bits are fixed cutter drill bits and roller cone drill bits. The cutter structure will vary according to the type of drill bit that is used, such as a PDC bit which uses polycrystalline diamond compact (PDC) cutters to shear rock with a continuous scraping motion, a tricone bit comprising three conical rollers with teeth breaking rock as the rollers move around, a diamond matrix, or other suitable cutter structures.

The transport screws, or conveying screws, are rotating screws arranged with one end near the cutting faces of the cutter structure in order to catch the cuttings produced during drilling. As the screws rotate, the cuttings are transported along the threads and are thus transported along the length of the screws. The second ends of the screws are arranged adjacent to the opening for further disposal of the cuttings.

In one embodiment the distance / gap, horizontally or vertically, between p+tefe ef- the transport screws is adapted to the maximum particle size to be transported. Alternatively or add itionally, the pitch of the transport screws may be adapted to the maximum particle size to be transported.

In this way the size of the particles of the cuttings may be limited, thus facilitating the subsequent disposal of the cuttings.

In one embodiment, the two transport screws are arranged to be counter rotating.

In one embodiment, the two transport screws are arranged to be co-rotating.

Arranging the screws counter rotating, causes a higher pressure in the threads, and thus more lift causing transport of the cuttings.

The opening is arranged in the drill bit and may be embodied in form of a duct or pipe or connected to a duct or pipe, which runs inside or outside of the drill bit to a location remote from the cutting structure. In the case where the drill bit is used with the autonomous device of N03121 10, the opening may run through the complete device and dispose the cuttings behind the device. In other embodiments, the opening may lead to other locations, for example along the sides of the drilling device for disposal along the drilling path.

The invention will now be described in more detail, and by reference to the accompanying figures.

Figure 1 shows a principle sketch of an embodiment of a drill bit according to the invention.

Figure 2 shows an embodiment of a drill bit with co-rotating transport screws. Figure 3 shows an embodiment of a drill bit with counter-rotating transport screws. Figure 4 shows an example of an embodiment of a drill bit used in an exploration device.

In figure 1 it is principally illustrated a drill bit 10. The drill bit 10 comprises a cutter structure 14 for breaking apart, cutting or crushing rock formations when drilling, at least one opening 1 3 in the drill bit for removal of cuttings from the cutter structure, and at least two transport screws 1 1 , 12 arranged in connection to the opening 13 for transporting cuttings into the opening and further to a location remote from the drill bit.

Further details are shown in figure 2, which shows an example embodiment where the transport screws 21 , 22 are arranged to be co-rotating. During use, the rotation of the drill bit 20 will activate the cutter structure 24. The cutter structure 24 will then cut into and release particles and larger parts of the ground or other material in which drilling is performed. These cuttings will initially surround the drill bit. In this embodiment the cutter structure 24 comprises guiding recesses 27 which will lead cuttings from the outside of the drill bit towards the centre of the drill bit 20. The two transport screws 21 , 22 are arranged side by side in the drill bit, with one end near the end of the guiding recesses 27, at the lower end of the drill bit. As the drill bit rotates, the cuttings will move along the guiding recesses 27 towards the transport screws, and will arrive at the receiving surface of the of the transport screws.

In other embodiments, the drill bit may have a different design, but an amount of the cuttings will nevertheless reach the receiving surface of the transport screws. Examples of drill bit designs can be the drill bit having longitudinal slits at its periphery reaching from the bottom and upwards, for example having a height approximately half the height of the bit, into which cuttings can flow and reach the transport screws.

The transport screws 21 , 22 rotates in the same direction (co-rotating), which in this example is the opposite rotation direction from the rotation of the drill bit. The rotation of the transport screws 21 , 22 will cause the cuttings to be lead along the threads of the transport screws and towards the opening 23. The transported cuttings entering the opening 23 will apply a pressure on the opening, and cause the cuttings to be further transported through the opening 23 and further away from the drill bit.

Figure 3 shows an embodiment of at drill bit similar to the embodiment shown in figure 2, but in this embodiment the transport screws 31 , 32 are caused to rotate in opposite directions (counter-rotating). The counter rotating movement of the transport screws 31 , 32, will in a way similar to that described in figure 2, cause the cuttings to move along the threads 36 of the transport screws and into the opening 33. The counter-rotating movement of the transport screws 31 , 32, creates a higher pressure of the cuttings on the opening 33 , and thus more lift causing further upward movement of the cuttings away from the drill bit. 30.

In figure 4 is shown an example of an embodiment of a drill bit 40 used in an exploration device, such as the device described in NO3121 10. As the drill bit 40 drills through a formation 49, the cuttings are guided through the opening 43, and further through a pipe 48. In this way the drill bit according to the invention may be used as a first step in a transport system. Following the drill bit in a transport system of the kind described in NO3121 10, is a pump or other conveyor means which causes the cuttings to be transported through the pipe 48 and into a compacting module which compacts the cuttings and deposits the compact cuttings behind the exploratton device at end 46 as a mass 47. The drill bit according to the invention may also be used in similar transport systems in other devices.