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.