Page 96 - Well Control for Completions and Interventions

88 Well Control for Completions and Interventions

Figure 3.1 A conventional multispool wellhead.
• Support the Christmas tree (if fitted) once the well is completed, and
while it is in service.
• Provide pressure barriers between each annulus and atmosphere.
• Provide annulus access through side mounted gate valves. On subsea
a
wells only the inner (A ) annulus can be accessed—all other annulus
are inaccessible and therefore effectively trapped.
• Where relevant, provide pressure tight exit spool for surface controlled
subsurface safety valve (SC-SSSV) control lines, instrument cables,
ESP cables, and other remotely operated downhole tools.
Many wells are still equipped with traditional, multiple spool well-
heads where each casing string is suspended from a separate and appropri-
ately sized casing spool. This means that each time a casing string is run

a
In this context “A” refers to the innermost (production) annulus. Most operating
companies, by convention, label each annulus starting with the innermost (A) and work
out. B is the intermediate and C the outer annulus. There are exceptions, however.
Some operators, particularly in Canada, label the outermost annulus A, since it is the
first to be installed and progress inwards. This can lead to confusion.