Drill bit assembly and method of performing an operation in a wellbore

1. A drill bit assembly comprising:

a bit body connectable to a tubular drill string, which bit body is provided with a longitudinal passageway therethrough for an operating tool to pass from an internal position in an attached drill string to an external position;

a closure element for closing the passageway when the closure element is in a closing position, which closure element is externally removable from the passageway; and

a passage tool attached to or connectable to the closure element in its closing position and disposed inside the bit body when the closure element is in a closing position,

wherein the passage tool comprises:

a lower part to which the closure element is attached or connectable, which lower part is arranged so that it can be moved out of the bit body together with the closure element, and

an upper tubular part which is arranged so that it can be moved along the passageway in the bit body, the upper tubular part forming a passage with a downstream opening for the passage of at least a portion of the operating tool to a position external to the passage tool, when the lower part of the passage tool has been moved out of the bit body.

2. The drill bit assembly according to claim 1 , wherein the passage tool is a hinge tool comprising a hinge joint between the upper and lower parts, in particular wherein the hinge joint is a double hinged joint.

3. The drill bit assembly according to claim 2 , wherein the hinge tool is arranged such that in a wellbore ahead of the bit body the lower part can pivot sufficiently with respect to the upper tubular part that the operating tool can be passed from an interior position to a position in the wellbore past the closure element.

4. The drill bit assembly according to claim 1 wherein the bit body has an axis and wherein the assembly is arranged to provide a passageway for a tool substantially parallel to or coaxial with the axis.

5. A method of performing an operation in a wellbore, which method comprises:

arranging a drill string in the wellbore with a drill bit assembly according to claim 1 at its lower end, and a distance above the bottom of the wellbore;

removing the closure element from its closing position on the bit body, and passing the closure element with the attached passage tool into the wellbore, to reach a position wherein the downstream opening of the upper part of the passage tool has passed through the passageway of the bit body, but wherein at least part of the upper tubular part still resides in the passageway of the bit body;

passing an operating tool from a position inside the drill string via the passage formed by the tubular drill string, bit body, and upper tubular part of the passage tool through the downstream opening of the upper part of the passage tool, to reach a position in the wellbore, and performing the operation.

6. The method according to claim 5 , wherein the passage tool is a hinge tool comprising a hinge joint between the upper and lower parts, and wherein the lower part is pivoted with respect to the upper part before or during passage of the operating tool through the downstream opening.

7. The method according to claim 5 , wherein the operation is selected from the group consisting of placement of an object, injecting a fluid into the wellbore; obtaining a sample from the wellbore; obtaining a sample from the formation surrounding the wellbore, for example obtaining a core sample or obtaining a fluid sample; performing a measurement.

8. The method according to claim 5 , wherein a plurality of operations are subsequently performed in the wellbore using different operating tools.