Wellstring assembly

1. A well-drilling bit assembly suitable for through-bit operation comprising a well-drilling bit, which includes

a bit body having upper and lower ends having a passageway there through, the bit body being attachable at its upper end to a tubular drill string and the passageway extending between an opening at the upper end and the exterior of the bit body;

a closure element for the passageway co-operating with the lower end of the bit body; and

a bit-connecting means for releasably connecting the closure element to the bit body so as to selectively close the passageway;

the well-drilling bit assembly further comprising an auxiliary tool for manipulating the closure element, which auxiliary tool is passable along the passageway in the bit body to the closure element when the bit body and closure element are interconnected with the bit-connecting means, which auxiliary tool comprises a tool-connecting means for selectively connecting the auxiliary tool to the closure element, and an operating means to operate the bit-connecting means which includes releasing the bit-connecting means,

and which auxiliary tool comprises a first member which includes the tool-connecting means and a second member which includes the operating means, which second member is movably arranged relative to the first member so that it is movable between a first and a second position relative to the first member, wherein in the first position the tool-connecting means is connectable, at least when the bit body and closure element are interconnected with the bit-connecting means, to the closure element whereby the bit-connecting means is not operable, and whereby in connected condition of the auxiliary tool with the closure element the bit-connecting means is operable by movement of the second member including the operating means between the first and the second position.

2. The well-drilling bit assembly according to claim 1 , wherein the tool-connecting means is arranged near the downstream end of the first member, wherein the operating means is arranged near the downstream end of the second member, and wherein the second member is arranged longitudinally slideably along the passageway with respect to the first member, so that the first relative position is an upstream position of the second member, and wherein the second member is moved relative to the first member in downstream direction when moving it towards the second relative position.

3. The well-drilling bit assembly according to claim 2 , wherein the first member of the auxiliaiy tool comprises a substantially tubular body in which the second member is coaxially slideably arranged, wherein the closure element comprises at its upstream end an outer sleeve and a coaxial inner sleeve, wherein the upstream end of the outer sleeve is arranged to cooperate with the tool-connecting means so as to lock the auxiliary tool to the outer sleeve, wherein the upstream end of the inner sleeve is arranged to cooperate with the operating means of the auxiliary tool so that the bit-connecting means is operated by longitudinally sliding the inner sleeve with respect to the outer sleeve.

4. The well-drilling bit assembly according to claim 3 , wherein the bit body further comprises an operable first retainer device for securing the second member of the auxiliary tool in the first relative position when the auxiliary tool is not connected to the closure element.

5. The well-drilling bit assembly according to claim 4 , wherein the bit body is provided with a button which projects into the passageway and co-operates with the first retainer device so as to operate the first retainer device at a predetermined relative position between the button and the first retainer device.

6. The well-drilling bit assembly according to claim 5 , further comprising a selectively operable second retainer device for securing the second member of the auxiliary tool in the second relative position when the auxiliary tool is connected to the closure element while the closure element is not connected to the bit body.

7. The well-drilling bit assembly according to claim 6 , wherein the bit body is provided with a button which projects into the passageway and co-operates with the second retainer device so as to operate the second retainer device at a predetermined relative position between the button and the second retainer device.

8. The well-drilling bit assembly according to claim 7 , wherein the passageway and the auxiliaiy tool are provided with co-operating angular orienting means.

9. The well-drilling bit assembly according to claim 8 , wherein the bit body and the auxiliary tool are provided with the co-operating angular orienting means for angularly orienting the auxiliary tool at a first relative position when moving downwardly along the passageway, and at a lower second relative position when moving upwardly again along the passageway.

10. The well-drilling bit assembly according to claim 9 , wherein the auxiliary tool at its outer wall is provided with an outwardly projecting key means, wherein the inner wall of the passageway in the bit body is provided with two guiding rims forming a central guiding groove through which the key can pass, the guiding groove having upstream and downstream ends, further with an upstream camming rim extending from a position upstream of the guiding groove to the upstream end of the guiding groove fully around the inner wall, and with a downstream camming rim extending from a position downstream of the guiding groove to the downstream end of the guiding groove fully around the inner wall, wherein the camning rims and the guiding rims project sufficiently into the passageway so as to engage, when the auxiliary tool is moved through the bit body, the key means and to guide the key means into the guiding groove, thereby angularly orienting the auxiliary tool.

11. A wellstring assembly comprising:

an upper tubular wellstring part having upper and lower ends between which ends a passageway is arranged;

a lower wellstring part having upper and lower ends which lower end is connectable to or includes a drill bit, the lower wellstring part co-operating with the lower end of the first wellstring part;

a releasable wellstring-interconnecting means for selectively interconnecting the lower and upper wellstring parts; and

an auxiliary tool arranged so that it can pass along the passageway in the upper wellstring part to the lower wellstring part, when the upper and lower wellstring parts are interconnected, wherein the auxiliary tool comprises a tool-connecting means for selectively connecting the auxiliary tool to the lower wellstring part, and an operating means for connecting or releasing the wellstring-interconnecting means,

wherein the auxiliary tool comprises a first member which includes the tool-connecting means and a second member which includes the operating means, which second member is arranged movably so that it can assume a first and a second position relative to the first member, wherein in the first position the tool-connecting means is connectable, at least when the upper and lower wellstring parts are interconnected, to the lower wellstring part without operating the wellstring-interconnecting means, and wherein after connecting the auxiliary tool to the lower wellstring part the wellstring-interconnecting means can be operated by moving the second member including the operating means between the first and the second position; and

wherein the upper wellstring part and the auxiliary tool are provided with co-operating angular orienting means for angularly orienting the auxiliary tool at a first relative position when moving downwardly along the passageway, and at a lower second relative position when moving upwardly again along the passageway.