Well drilling bit

1. A well drilling bit comprising:

a bit body attachable to a tubular drill string, which bit body is internally provided with a passageway other than a nozzle, which passageway provides fluid communication, when the drill string is attached to the bit body, between the interior of the drill string and the exterior of the bit body;

a closure element for selectively closing the passageway; and

one or more chip-making elements,

wherein the chip-making elements comprise one or more roller-cones, wherein the closure element is releasably connectable to the bit body, and outwardly movable from a closing position, in which the closure element is connected to the bit body, to an opening position, in which the closure element is disconnected from the bit body, wherein the closure element includes at least one of the roller-cones and a cone leg, and wherein the passageway comprises a section that is not co-axial with the central longitudinal axis.

2. The well drilling bit according to claim 1 , wherein the well drilling bit with the closure element in the closing position has substantially the form of a bit selected from the group consisting of a roller-cone bit, a tricone roller-cone bit, a pentacone roller-cone bit, a reamer bit, and a bicenter bit.

3. The well drilling bit according to claim 1 , wherein the well drilling bit without the closure element substantially has the form of a coring bit.

4. The well drilling bit according to claim 1 , wherein the cone leg functions as a carrier element for the at least one roller cone.

5. The well drilling bit according to claim 1 , wherein the closure element is provided with bit latching means for selectively latching the closure element to the bit body.

6. A well drilling bit comprising:

a bit body attachable to a tubular drill string, which bit body is internally provided with a passageway other than a nozzle, which passageway provides fluid communication, when the drill string is attached to the bit body, between the interior of the drill string and the exterior of the bit body;

a closure element for selectively closing the passageway; and

one or more chip-making elements,

wherein the chip-making elements comprise one or more roller-cones, wherein the closure element is releasably connectable to the bit body, and outwardly movable from a closing position, in which the closure element is connected to the bit body, to an opening position, in which the closure element is disconnected from the bit body, wherein the closure element includes at least one of the roller-cones, and wherein the passageway comprises a section that is not co-axial with the central longitudinal axis, wherein the closure element is arranged to stay clear of a wellbore wall formed during normal operation of the drilling bit when the closure element is moved from the closing position to the opening position.

7. A well drilling bit comprising:

a bit body attachable to a tubular drill string, which bit body is internally provided with a passageway other than a nozzle, which passageway provides fluid communication, when the drill string is attached to the bit body, between the interior of the drill string and the exterior of the bit body;

a closure element for selectively closing the passageway; and

one or more chip-making elements,

wherein the chip-making elements comprise one or more roller-cones, wherein the closure element is releasably connectable to the bit body, and outwardly movable from a closing position, in which the closure element is connected to the bit body, to an opening position, in which the closure element is disconnected from the bit body, wherein the closure element includes at least one of the roller-cones, and wherein the passageway comprises a section that is not co-axial with the central longitudinal axis, wherein the closure element forms a pilot drill bit.

8. A well drilling bit comprising:

a bit body attachabled to a tubular drill string, which bit body is internally provided with a passageway other than a nozzle, which passageway provides fluid communication between the interior of the drill string and the exterior of the bit body;

a closure element for selectively closing the passageway; and

one or more chip-making elements,

wherein the chip-making elements comprise one or more roller-cones, wherein the closure element is releasably connectable to the bit body, and outwardly movable from a closing position, in which the closure element is connected to the bit body, to an opening position, in which the closure element is disconnected from the bit body, wherein the closure element includes at least one of the roller-cones, and wherein the passageway comprises a section that is not co-axial with the central longitudinal axis, and wherein there is further provided an auxiliary tool comprising connecting means for selectively connecting the auxiliary tool to the closure element, and wherein the interior of the drill string and the passageway of the bit body are arranged to allow the auxiliary tool to pass from a position in the drill string to the closure element.

9. The well drilling bit according to claim 8 , wherein the auxiliary tool comprises two or more longitudinal sections which are hingedly connected.

10. The well drilling bit according to claim 8 , wherein the passageway of the bit body is arranged to allow the auxiliary tool to pass to the exterior of the bit body, when the closure element has been removed from the bit body.

11. The well drilling bit according to claim 8 , wherein the connecting means of the auxiliary tool comprises a tool latching means for latching the auxiliary tool to the closure element.

12. The well drilling bit according to claim 11 , wherein the closure element is provided with bit latching means for selectively latching the closure element to the bit body.

13. The well drilling bit according to claim 12 , wherein the tool latching means and the bit latching means are arranged so as to unlatch the closure element from the bit body upon latching of the auxiliary tool to the closure element.

14. A well drilling bit comprising:

a bit body attachable to a tubular drill string, which bit body is internally provided with a passageway other than a nozzle, which passageway provides fluid communication, when the drill string is attached to the bit body, between the interior of the drill string and the exterior of the bit body;

a closure element for selectively closing the passageway; and

one or more chip-making elements,

wherein the chip-making elements comprise one or more roller-cones, wherein the closure element is releasably connectable to the bit body, and outwardly movable from a closing position, in which the closure element is connected to the bit body, to an opening position, in which the closure element is disconnected from the bit body, wherein the closure element includes at least one of the roller-cones, and wherein the passageway comprises a section that is not co-axial with the central longitudinal axis, wherein the closure element further includes a carrier element for each included roller-cone.

15. A well drilling bit comprising:

a bit body attachable to a tubular drill string, which bit body is internally provided with a passageway other than a nozzle, which passageway provides fluid communication, when the drill string is attached to the bit body, between the interior of the drill string and the exterior of the bit body;

a closure element for selectively closing the passageway; and

one or more chip-making elements,

wherein the chip-making elements comprise one or more roller-cones, wherein the closure element is releasably connectable to the bit body during an operation when the bit body is located in a wellbore, whereby the closure element is outwardly movable from a closing position, in which the closure element is connected to the bit body, to an opening position, in which the closure element is disconnected from the bit body, wherein the closure element includes at least one of the roller-cones, and wherein the passageway comprises a section that is not co-axial with the central longitudinal axis.

16. The well drilling bit according to claim 15 , wherein the closure element includes a cone leg.

17. Method of drilling a wellbore, comprising

providing a well drilling bit comprising:

a bit body attachable to a tubular drill string, which bit body is internally provided with a passageway other than a nozzle, which passageway comprises a section that is not co-axial with the central longitudinal axis, which passageway provides fluid communication, when the drill string is attached to the bit body, between the interior of the drill string and the exterior of the bit body;

one or more chip-making elements, the chip-making elements comprising one or more roller-cones;

a closure element for selectively closing the passageway, the closure element including at least one of the roller-cones;

lowering the well drilling bit to a bottom of a wellbore;

applying drilling torque to the well drilling bit with the closure element in a closing position;

pulling the well drilling bit up sufficiently far from the bottom of the wellbore in order that there is enough space in the wellbore ahead of the well drilling bit for bringing the closure element in an opening position;

moving the closure element outwardly into the wellbore, from the closing position, in which the closure element is connected to the bit body, to the opening position, in which the closure element is disconnected from the bit body.

18. The method of claim 17 , further comprising

returning the closure element to the closing position while the well drilling bit is located in the wellbore.

19. The method of claim 18 , wherein moving the closure element outwardly into the wellbore to the opening position comprises lowering an auxiliary tool from a position inside the drill string to enter the bit body, and returning the closure element to the closing position comprises retracting the auxiliary tool.

20. The method of claim 17 , wherein moving the closure element outwardly into the wellbore to the opening position comprises lowering an auxiliary tool from a position inside the drill string to enter the bit body.

21. The method of claim 17 , wherein moving the closure element outwardly into the wellbore comprises allowing a measurement section to enter the space in the wellbore exterior of the drilling bit.