ROV deployed tree cap for a subsea tree and method of installation

A method for installing a subsea Xmas tree cap on a subsea Xmas tree above the mudline;

• the subsea Xmas tree having a projecting upper hub to receive the tree cap including a production bore and an annulus bore, said upper hub having an outer peripheral surface and an inner peripheral surface;
• the method comprising the steps of:
• providing the tree cap with an outer latch means for latching into the outer peripheral surface of said upper hub, a fluid operated inner latch means for latching onto the inner peripheral surface of said upper hub, and a seal plate for sealing the production bore and the annulus bore;
• lowering the tree cap onto said hub,
• latching said cap with said outer latch means onto the outer surface of said hub;
• moving said seal plate downwardly relative to said tree cap against said projecting upper hub of said Xmas tree to provide a sealing relation with said production bore and annulus bore;
• and
• then latching said seal plate with said fluid operated inner latching means to the inner peripheral surface of said upper hub.

A lightweight ROV deployable tree cap for a subsea tree having a projecting production hub and an outer funnel guide supported on the hub with alignment means on the guide for the cap said cap comprising:

• a lightweight elongate non-metallic cap body extending across the funnel guide and supported thereon in an aligned position with the subjacent hub on the tree;
• a seal plate member mounted on said cap body for relative movement and positioned over a production bore of the hub;
• and
• fluid pressure means for forcing said seal plate member downwardly relative to said cap body into a sealed landed position with the production bore of said hub.

A lightweight ROV deployable tree cap for a subsea tree having an upper production hub including a production bore, and an annulus bore;

• said tree cap comprising:
• a lightweight non-metallic body having a plurality of openings and bores therein for mounting of operating elements of said tree cap thereon for latching onto said hub and for sealing said production and annulus bores;
• said operating elements including latch means for initially latching externally onto said hub prior to sealing of said production and annulus bore;
• and
• hydraulically actuated sealing means movable relative to said body for sealing said production and annulus bores after said latch means has latched onto said hub.

A lightweight ROV deployable tree cap for a subsea tree having a hub with a production bore therein;

• said ROV deployable tree cap comprising:
• a lightweight non-metallic body having a plurality of predetermined mounting positions for mounting a plurality of operating assemblies thereon for coupling onto said hub and sealing against said production bore;
• said operating assemblies including:
• coupling means for coupling said tree cap onto said hub;
• and
• hydraulically operated sealing means for sealing said production bore after coupling of said coupling means to said hub.