Page 246 - Well Control for Completions and Interventions

240 Well Control for Completions and Interventions

• Running wireline deployed pressure gauges to obtain an accurate
BHP measurement. A gradient survey can also locate water/oil and
oil/gas contacts in the wellbore.
• Running caliper or sonic logs to determine the condition of the
tubing and casing.
• Creating a flow path between production tubing and casing for
circulating kills, for example opening a sliding sleeve or punching a
hole in the tubing.
• Performing the well kill (circulating or non-circulating).
• Installing mechanical barriers in preparation for the removal of the
Christmas tree and the installation of the BOP.

7.3 WELL KILL: REVERSE CIRCULATION

Although bullheading is the most commonly used method for
killing a production well prior to workover, it is not necessarily the best.
Reverse circulating is sometimes preferred, as surface pressure is generally
very low and formation damage is less likely. Kill weight brine is pumped
into the annulus, returning through the production tubing to the surface.
The natural U tube effect created by the heavy fluid in the annulus helps
push the lighter hydrocarbon in the tubing towards the surface and in
most cases, a single circulation (combined volume of annulus and tubing)
is enough to kill the well. The advantages of a reverse circulation kill are:
• Pump pressure is normally lower than a bullhead.
• Little or no formation damage occurs. If properly performed, fluid
loss to the formation should be minimal and is eliminated if the well
can be plugged below the circulation point.
• It is the shortest (quickest) route to circulate hydrocarbons in the
tubing to the surface.
• If the Christmas tree is still in place and the flowline still connected,
hydrocarbons can be produced to the production facilities for easy,
low risk, disposal.
Note: Some remotely operated production chokes are not ideal for control-
ling flow from the well and may have to be by-passed, with flow routed
through a manually operated choke. Nevertheless, the tubing contents can still
be routed through the process facilities.