Numerous developments in automation have made the modern mobile offshore drilling unit a marvel of engineering achievement and a model of efficiency. Yet, even with the surge in advancements, kick detection, which can be comparatively elementary for a fixed drilling unit, has proved to be significantly more difficult to master on a vessel subject to wave motion and currents. This paper describes experiences, challenges, and approaches to solving the problems related to creating an advanced early kick-detection system suitable for floating mobile offshore drilling units.
The complete paper provides a discussion of conventional approaches to kick detection. However, managed-pressure drilling (MPD) has surfaced as a natural response to drilling in unconventional or otherwise difficult fields, and the need for an enhanced kick-detection system has been established somewhat naturally from the imposed needs of MPD systems. MPD is based upon the most fundamental principles of drilling; balancing the equivalent circulating density to formation pressure minimizes influx and stabilizes the wellbore. The MPD system aims to drill a well within a margin of the balanced pressure of the formations being drilled. To accomplish this goal, a rotary head or other annular sealing device is coupled with an active drilling choke that can automatically adjust the casing pressure. Though configurations of the MPD system may vary, the primary feedback mechanism for the MPD system in all cases is the return flow rate. When bottomhole pressure (BHP) is lower than formation pressure, influx of formation fluid occurs.
Closing the system with an annular seal offers many benefits. The closed system creates a fixed, known well volume that is a function of the casing and bit diameters and the volume occupied by the drillstring. With fluid in the wellbore being mostly incompressible, the pressure upstream of the choke and the flow rate through the return line become valuable in determining the size and severity of kicks. Sealing the wellbore has also led to the use of meters that can measure multiphase flow accurately. Conventionally, wellbore and fluid characteristics are determined by analyzing trends and catching samples after the fact, whereas a closed-loop system allows a higher level of automation, real-time automated analysis, and actionable data on the basis of which engineers can quickly make decisions....
Advancing Deepwater Kick Detection
01 May 2016