As the industry continues to expand into ultradeepwater plays, an
increasing number of tight tolerance wells warrant the use of an efficient
system for determining early influxes or losses during drilling, tripping, and
cementing operations. The narrow mud weight window for the majority of these
wells requires an advanced solution in order to operate in all such conditions
without compromising on safety. This paper describes a new early detection flow
monitoring system and setup for floating rigs, and presents its application via
a case study of a very high-profile ultra deepwater well.
Good well surveillance for floating rigs requires precise measurements
combined with an efficient smart process adapted to deepwater conditions in
order to raise a reliable alarm in any condition, while minimizing the risk of
false alarms. Careful sensor selection and sizing, together with particular
attention to installation is required in order to achieve this degree of
accuracy for all the drilling phases. The solution described in this case study
provides drilling surveillance for all hole sizes, with flow up to 2000 gpm for
accurate and early detection, and significantly increased safety during
drilling, tripping, and cementing operations.
This case study describes how kicks can be detected with a high degree
of reliability much earlier than with the standard pit volume and flow paddle
monitoring. In addition to this, it has shown its value by characterizing, in
real time, the consequences following a packoff event and also by
differentiating between a wash out and pump failure.
Crew confidence in this detection system rapidly led to modifications
of the operational procedures. For instance, flow checks were previously done
for every pipe connection, taking up expensive rig time. Due to results
obtained in the previous hole sections, the drilling procedures were updated in
order to significantly reduce time spent flow-checking, while still maintaining
maximum safety during the operations.
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