Abstract: A downhole barrier system comprising: a wellbore; an upper packer; upper barrier valve; a pressure sensor; a ported sub; a lower packer; a lower pack flow port sliding sleeve; and a lower barrier valve.

Abstract: A system for performing a desired subsea well-servicing operation, comprises a vessel, a service apparatus for performing the desired subsea well-servicing operation, the service apparatus being supported on the vessel; and a support apparatus mounted on the vessel, the support apparatus having first and second modes, wherein in the first mode the support means does not provide access to a well by the service apparatus and wherein in the second mode the support means does provide access to a well by the service apparatus. The vessel may be a vessel of opportunity and the service apparatus may be selected from the group consisting of subsea tree installation apparatus, perforating apparatus, acidizing apparatus, fracturing apparatus, workover apparatus, reservoir stimulation apparatus, wireline apparatus, coiled tubing apparatus, and snubbing apparatus.