Deepwater drilling brings a highly demanding set of economic and operational challenges. Many of the well construction methods and technologies used for decades are now less than optimal in extreme subsea environments.

The future of deepwater assets requires innovation that brings a new measure of risk mitigation and economic enhancement to the task.

Fortunately, many of the answers are already at hand. For example, in deepwater basins around the world, the rapidly advancing capabilities of managed-pressure drilling (MPD) are setting new levels of performance for risk mitigation and operational and economic efficiency. The methodology has advanced well construction capabilities so that, in many cases, what was once undrillable now makes a good prospect.

Along with other non-traditional well construction methods such as expandable tubulars and drilling-with-casing, MPD approaches wellbore construction in novel ways. But the rewards are great because with these advances, the industry stands at the threshold of a bright new future in deepwater exploration and development.

Closing the loop
Based on a closed-loop circulating system rather than a traditional system that is open to the atmosphere, MPD provides exceptional results where conventional drilling methods are struggling or have failed entirely – from extreme lost-circulation conditions to threading exceedingly narrow drilling windows.

This success is the result of careful planning and engineering for the specific application. MPD is not a casual application of last-minute, bolt-on hardware, especially in deep water. With a variety of configurations, the optimal system must be selected and engineered based on a wide scope of variables, from well conditions and objectives to the rig design and the skills of its crew.

The hardware and software applied in deepwater MPD run the gamut from automated chokes to specialized marine rotating control devices matched to heave compensation systems. Computerized systems using sophisticated algorithms enable MPD techniques to move beyond drilling operations to provide a diagnostic window on the well bore.

The capabilities allow MPD to effectively close the loop on hazard mitigation by providing actionable information on what is happening downhole. For instance, using easily understood and applied data, the driller can tell if the well is breathing during a connection or taking a kick – and can act accordingly.
In this respect, an MPD system is the foundation for integrating many rig activities in a holistic approach to well construction. There already are examples of how that integration takes place.

For instance, Weatherford’s mud logging group has a gas chromatograph instrument that characterizes hydrocarbons in the system. When this is used within an MPD system’s circular loop with fluids flowing through it, gas influx can not only be seen, it can be characterized. That assessment takes place in real time while circulating the well.

In one series of North Sea wells, Weatherford was to perform early kick detection. With a closed-loop system, it was possible to identify gas stringers vs. kick events without having to shut down. The system then was applied more robustly to drill through the stringers.

When the gas chromatograph was added to the loop, the crew was able to get a better understanding of the well’s behavior. After every connection, the traditional mud logging system showed gas exiting the fluids, but the chromatograph detected no hydrocarbons and showed conclusively that it was a false reading.

As a result, the percolation time required before drilling ahead after each connection was reduced, saving a considerable amount of time. In total, the combined system saved about 75 days when compared to the previous well.

The deepwater path
This capability would not be possible without the closed-loop circulating system at the heart of MPD methodologies, nor would these benefits have been realized.

As the industry considers the path ahead in deepwater well construction, the use of MPD and other novel methods becomes paramount. These extremes are like nothing the industry has faced before; the solutions must share in that uniqueness to achieve success.

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