is that installed choke 38 may be easily retrieved via tree cap 24 while requiring only two vertical boreholes in tree cap 24 this allows the use of a workover riser embodying only two vertical conduits to service the well during necessary workover operations the operation of the embodiment shown in fig2 is similar to the operation of the embodiment in fig1 discussed above except that hub isolation valve 54 must also be opened for flow through choke 38 this allows flow from choke 38 to go directly to production line 32 instead of back through tree cap 24 and tree annulus passage 26 for maintenance it is first necessary to isolate the tree cap 24 from the wellbore and the other production facilities with annulus crown valve 30 and annulus master valve 28 in a closed position production master valve 20 production crown valve 22 production wing valve 34 and hub isolation valve 54 are shut the connector joining tree cap 24 to subsea tree assembly 10 is then released choke return hub connection 50 is simultaneously released tree cap 24 choke 38 and the tree cap side of hub connection 50 are then brought to the surface for repair or replacement in addition to the aforementioned ease of choke retrieval the advantages of the arrangement shown in fig2 is that the wellbore may be produced through tree assembly 10 even after subsea choke 38 experiences a failure this may be accomplished by closing production crown.