Nested velocity string tubing hanger

1. A wellhead assembly, comprising:

a wellhead housing;

an outer tubing hanger for securing to an outer string of tubing, the outer tubing hanger being landed in the wellhead housing, the outer tubing hanger having a production passage for receiving well fluid flowing up the outer string of tubing while in a first mode; and

while in a second mode, an inner tubing hanger for securing to an inner string of tubing, the inner tubing hanger having a lower portion that is landed sealingly in the production passage of the outer tubing hanger, the inner tubing hanger having a production passage for receiving well fluid flowing up the inner string of tubing while in the second mode;

a tree connected to the wellhead housing, the tree having a production passage;

while in the first mode, an isolation tube extending from sealing engagement with the production passage of the outer tubing hanger to sealing engagement with the production passage of the tree; and

while in the second mode, the isolation tube being removed and the inner tubing hanger having an upper portion extending into sealing engagement with the production passage of the tree.

2. A wellhead assembly, comprising:

a wellhead housing;

an outer tubing hanger for securing to an outer string of tubing, the outer tubing hanger being landed in the wellhead housing, the outer tubing hanger having a production passage for receiving well fluid flowing up the outer string of tubing while in a first mode; and

while in a second mode, an inner tubing hanger for securing to an inner string of tubing, the inner tubing hanger having a lower portion that is landed sealingly in the production passage of the outer tubing hanger, the inner tubing hanger having a production passage for receiving well fluid flowing up the inner string of tubing while in the second mode;

a lock member extending between a profile in the production passage of the outer tubing hanger and a profile on an exterior portion of the inner tubing hanger for locking the inner tubing hanger to the outer tubing hanger.

3. The assembly according to claim 2 , wherein:

in the second mode, the lower portion of the inner tubing hanger lands on a shoulder within the production passage of the outer tubing hanger.

4. The assembly according to claim 2 , further comprising:

an outer penetrator passage extending through the outer tubing hanger for connecting to a hydraulic line extending alongside the outer string of tubing; and

an inner penetrator passage extending through the inner tubing hanger for connecting to a hydraulic line extending alongside the inner string of tubing.

5. A wellhead assembly, comprising:

a wellhead housing;

an outer tubing hanger for securing to an outer string of tubing, the outer tubing hanger being landed in the wellhead housing, the outer tubing hanger having a production passage for receiving well fluid flowing up the outer string of tubing while in a first mode; and

while in a second mode, an inner tubing hanger for securing to an inner string of tubing, the inner tubing hanger having a lower portion that is landed sealingly in the production passage of the outer tubing hanger, the inner tubing hanger having a production passage for receiving well fluid flowing up the inner string of tubing while in the second mode;

an outer tubing annulus port extending laterally through a sidewall of the wellhead housing for communicating with an outer tubing annulus surrounding the outer string of tubing;

an inner tubing annulus port extending laterally through the sidewall of the wellhead housing above the outer tubing annulus port; and

an inner tubing annulus port extending from the production passage in the outer tubing hanger laterally through a sidewall of the outer tubing hanger and in communication with the inner tubing annulus port in the wellhead housing, for communicating with an inner tubing annulus between the inner and outer strings of tubing while in the second mode.

6. A wellhead assembly, comprising: a wellhead housing;

an outer tubing hanger for securing to an outer string of tubing, the outer tubing hanger being landed in the wellhead housing, the outer tubing hanger having a production passage for receiving well fluid flowing up the outer string of tubing while in a first mode; and

while in a second mode, an inner tubing hanger for securing to an inner string of tubing, the inner tubing hanger having a lower portion that is landed sealingly in the production passage of the outer tubing hanger, the inner tubing hanger having a production passage for receiving well fluid flowing up the inner string of tubing while in the second mode;

a split lock ring carried by the inner tubing hanger and engaging a profile in the production passage of the outer tubing hanger; and

a threaded section in the production passage of the outer tubing hanger above the lock ring for selectively receiving a release member to cam the lock ring out of engagement with the profile.

7. A wellhead assembly, comprising:

a wellhead housing;

an outer tubing hanger secured to an outer string of tubing and landed in the wellhead housing, the outer tubing hanger having an outer tubing hanger production passage;

an outer tubing hanger seal that seals between the outer tubing hanger and the wellhead housing;

a Christmas tree having a tree production passage and connected to the wellhead housing;

while in a first mode, an isolation tube extending between the tree and the outer tubing hanger production passages for conveying well fluid flowing up the outer string of tubing, the isolation tube being removed while in a second mode, the isolation tube having a lower end that stabs sealingly into the outer tubing hanger production passage and an upper end that stabs sealingly into the tree production passage in the first mode;

while in the second mode, an inner tubing hanger secured to an inner string of tubing, the inner tubing hanger having a lower portion landed in the outer tubing hanger production passage, and an upper portion that extends into sealing engagement with the tree production passage for conveying well fluid flowing up the inner string of tubing while in the second mode; and

an inner tubing hanger seal that seals between the inner tubing hanger and the outer tubing hanger production passage.

8. The assembly according to claim 7 , further comprising:

an outer hydraulic line extending alongside the outer string of tubing;

an outer penetrator passage connected to the outer hydraulic line and extending through the outer tubing hanger from below to above the outer tubing hanger seal;

an inner hydraulic line extending alongside an outer side of the inner string of tubing within the outer tubing; and

an inner penetrator passage connected to the inner hydraulic line and extending through the inner tubing hanger from below to above the inner tubing hanger seal.

9. The assembly according to claim 7 , further comprising:

a wellhead housing outer tubing annulus port extending laterally through a sidewall of the wellhead housing below the outer tubing hanger seal in communication with an outer tubing annulus surrounding the outer string of tubing;

a wellhead housing inner tubing annulus port extending laterally through the sidewall of the wellhead housing above the outer tubing hanger seal; and

an outer tubing hanger inner tubing annulus port extending from the outer tubing hanger production passage laterally through a sidewall of the outer tubing hanger and in communication with the wellhead housing inner tubing annulus port; and

while in the second mode, the inner tubing hanger seal being located above the point where the outer tubing hanger inner tubing annulus port joins the outer tubing hanger production passage, so that an inner tubing annulus between the inner and outer strings of tubing is in communication with the wellhead housing inner tubing annulus port.

10. The assembly according to claim 9 , wherein the isolation tube blocks access from the outer tubing to the outer tubing hanger inner tubing annulus port while in the first mode.

11. The assembly according to claim 7 , further comprising:

a split lock ring carried by the inner tubing hanger and engaging a profile in the outer tubing hanger production passage.

12. A method for producing a well, comprising:

securing an outer tubing hanger having a production passage to an outer string of tubing and landing the outer tubing hanger in a wellhead member;

while in a first mode, flowing the well fluid up the outer string of tubing and the production passage;

for a second mode, lowering an inner string of tubing into the outer string of tubing;

securing an inner tubing hanger to the inner string of tubing and landing and sealing a lower portion of the inner tubing hanger in the production passage of the outer tubing hanger; and

flowing the well fluid up the inner string of tubing,

locking the inner tubing hanger to the outer tubing hanger.

13. The method according to claim 12 , further comprising:

while in the second mode, communicating a tubing annulus between the outer and inner tubing strings with an exterior portion of the wellhead member.

14. The method according to claim 12 , wherein the outer tubing hanger has am outer penetrator passage that communicates an outer hydraulic line extending along the outer string of tubing with an exterior portion of the wellhead member; and wherein the method further comprises:

for the second mode, extending an inner hydraulic line alongside the inner string of tubing and providing the inner tubing hanger with a inner penetrator passage that communicates the inner hydraulic line with an exterior portion of the wellhead member.

15. The method according to claim 12 , further comprising:

providing the wellhead member with a laterally extending passage;

providing the outer tubing hanger with a laterally extending passage leading from the production passage into communication with the laterally extending passage in the wellhead member;

blocking any flow through the laterally extending passages while in the first mode; and

allowing flow from a tubing annulus between the inner and outer strings of tubing through the laterally extending passages while in the second mode.

16. The method according to claim 12 , further comprising:

for the first mode, landing a Christmas tree on the wellhead member and flowing the well fluid from the production passage in the outer tubing hanger to the tree; and

for the second mode, removing the tree to run the inner string of tubing and the inner tubing hanger, then replacing the tree on the wellhead member and flowing the well fluid from the inner tubing hanger to the tree.

17. The method of claim 12 , further comprising:

for the first mode, landing a Christmas tree on the wellhead member, providing an isolation tube extending between the production passage in the outer tubing hanger and a passage in the tree, and flowing the well fluid from the production passage in the outer tubing hanger through the isolation tube to the passage in the tree; and

for the second mode, removing the tree and the isolation tube to run the inner string of tubing and the inner tubing hanger, then replacing the tree on the wellhead member, extending an upper portion of the inner tubing hanger into sealing engagement with the passage in the tree, and flowing the well fluid from the inner tubing hanger into the passage in the tree.