moved horizontally within the well bay without disconnecting either the drilling bop 26 or the drilling riser tensioner system 30 moreover the drilling riser itself may remain in the sea in certain embodiments a dummy wellhead may be provided on the seafloor for landing and securing the lower end of the drilling riser while production risers are run this can help to prevent collisions between the risers fig6 contains four views of a transport trolley 32 according to one embodiment of the invention u2014 fig6 a is an isometric view fig6 b is a top plan view fig6 d is a side view and fig6 c is an end view adapter frame lift cylinders 60 are shown within transport trolley 32 also shown are openings 62 for guidelines 24 which may be sized to also permit passage of the remote rov guide post tops see fig8 fig7 contains four views of an adapter frame 66 according to one embodiment of the invention u2014 fig7 a is an isometric view fig7 b is a top plan view fig7 d is a side view and fig7 c is an end view adapter frame 66 has a central opening 67 with a perimeter rim 74 which may project into opening 67 rim or flange 74 may be sized and configured to fit drilling riser tensioner system 30 drilling riser tensioner system.