thus increasing drilling time before having to bring the stack to the surface for maintenance referring now to fig4 a drilling site may comprise a wellhead 18 and a parking pile 52 parking pile 52 provides a location for the subsea storage of an additional abp 16 a first abp 16 can be run as described above in reference to fig3 a by service vessel 48 bop stack 14 and lmrp 16 can then be run by a drilling rig and drilling operations performed using the ram bop 39 s in abp 16 before the useful life of the ram bop 39 s in abp 16 is reached a replacement abp 16 a can be run by a service vessel and landed on parking pile 52 when the first abp 16 needs to be serviced stack 14 and lmrp 12 can be disconnect from the abp but remain subsea once abp 16 is pulled to the surface for servicing replacement abp 16 a can be disconnected form parking pile 52 and landed on wellhead 18 replacement abp 16 a can be moved from parking pile 52 to wellhead 18 by drilling rig 50 by landing bop stack 14 on abp 16 a and then moving the entire assembly together replacement abp 16 a can also be moved onto wellhead 18 by a service vessel as bop stack 14 is supported by the drilling rig referring now to fig5 a 5c multiple abp systems 16 a 16 b can be used to drill multiple wells on a plurality of wellheads 18 a 18 c a first abp 16 a can be deployed onto wellhead 18 a with bop.