Closed-loop system can improve safety, improve drilling efficiency

David Pavel, director of business development, drilling optimization services for Weatherford International, posed the question of whether safety improvement can increase drilling efficiency during his presentation at the 2011 SPE/IADC Drilling Conference on 1 March in Amsterdam. His answer to the question was “hopefully yes.”

According to Mr Pavel, use of a closed-loop system can provide the ability to differentiate breathing/ballooning from an actual influx and allows one to fingerprint the well.

“The well control incident rate for normally pressured and temperature wells is about one in 20, still a fairly significant level in our industry,” he said. “These statistics tell us that there’s at least two incidents per well. That’s pretty alarming.” Impacts on open-atmosphere systems allow shallow-gas flows to surface, which could damage the rig, equipment and personnel. Lost-circulation zones, maintaining narrow pore pressure/fracture gradient and drilling in HPHT reservoirs can be hazardous.

Rotating control devices, flow-metering technologies, automated drilling choke systems and downhole isolation valves add incremental benefits and increase safety. When paired or used in combination to create a closed and pressurizable mud return system, the benefits escalate exponentially.

Further, when these devices are used to form a closed-loop circulating system, a contained circuit of incompressible drilling fluid is created and the mud system becomes a sensitive instrument that can provide real-time pressure and flow data. According to Mr Pavel, such a closed-loop system can detect kicks quickly and accurately to the degree of a couple of barrels. A normal-sized kick would be 10 barrels to 15 barrels. Use of a closed-loop system allows one to discern the difference between the wellbore breathing/ballooning and an actual kick.

In a closed-loop system, a rotating control device is used to maintain a seal on the drill pipe, creating a seal between the pipe and the casing annulus and diverts the fluid to a drilling choke manifold. “A closed-loop process does not change well control procedures,” Mr Pavel said. “All of the conventional measurements are used, but algorithms are also used in this system to allow us to see the variances that we need to.”

Closed-loop drilling “gives us visibility into the wellbore,” he said. “That allows us to create certainty where there was uncertainty. These systems allow us to obtain the actual pressure and gradients and actively manage the wellbore.”

“It does start with planning. If you’re going to use a closed-loop system, you need some upfront planning for logistics, for landing the equipment on the rig, everything from personnel training and an understanding of what will be done on location,” Mr Pavel said. “It does require pretty intense planning to deploy a closed-loop system.”

More information on this presentation can be found in SPE/IADC 139845, “Can Safety Improvement Increase Drilling Efficiency,” by David Pavel, Said Boutalbi and Brian Grayson, Weatherford International, presented at the 2011 SPE/IADC Drilling Conference, 1-3 March, Amsterdam.