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Fig. 4 – Hydrate removal layout
such as inhibitors circulation in proximity of
hydrate formation or mechanical removal tools.
Level 3
Flowline abandon and replacement with a new one.
An evaluation based on estimated possibilities
of success showed an economic advantage in
performing Level 1 plus Level 2 steps, aiming to the
maximum anticipation of injection recovery and its
positive effects on production, rather than choosing
Level 3 approach, with the highest chances of a
positive outcome but leading to a consistent delay
in resumption.
Depressurization sequence
Main idea of Level 1 flowline depressurization at bed
consisted in removing C/WO riser brine content
and replacing it with nitrogen, hence achieving a
strong reduction of hydrostatic pressure acting on
flowline. This operation was performed pumping
nitrogen from topside and recovering brine from
tubing hanger production bore, XT cross-over
Success of removal operation was
strongly based on preliminary gathering
information activity: performing two
different investigations, working on
independent principles, was found to
be of outmost importance, to cross-
check survey outcomes and avoid
interpretation mistakes.
Impiantistica Italiana - Settembre-Ottobre 2015 53