Page 228 - Well Control for Completions and Interventions

222 Well Control for Completions and Interventions

Figure 6.1 Horner plot example.

before infinite time (Horner time 5 1) the leak is diminishing and the
inflow test is good. If the plot makes an intersect of the y axis, it means
there is flow at infinite time and the inflow test has failed (Fig. 6.1).

6.5 NONCONFORMANCE WITH BARRIER POLICY
Many workover and intervention operations are performed to repair
or replace worn and damaged equipment that threatens the integrity of
the well. In some cases, the condition of the well is such that installing
two mechanical barriers may not be possible. Consider a situation where
barriers are needed to enable the Christmas tree to be removed and the
drilling BOP installed. Consider also that the reason for the intervention
is a need to replace the production tubing that has parted just below the
tubing hanger. In such a situation, a fluid barrier plus a mechanical plug
set in the tubing hanger nipple profile may be all that can be achieved.
In exceptional circumstances, and after a rigorous examination of the
risks, dispensation from normal barrier policy may be granted and per-
mission to proceed given. Much will depend on the conditions at the
well site. Factors influencing that decision will include reservoir pressure
and the nature of the reservoir, GOR, the quantity of H 2 S, and the gen-
eral condition of the wellhead and Christmas tree.