Brazil hosted its first annual OTC conference the first week of October 2011. The turnout was fair, and much like the Houston show, discussions on innovative technology were everywhere.

The technical session, Drilling – Operations and Engineering, held October 4, focused on several topics, but big news involved recent developments in managed pressure drilling (MPD) and its potential to impact future well designs.

With Brazil’s deepwater potential, MPD is fast becoming the method of choice for offshore exploration wells. According to Muarizio Arnone, drilling hazard mitigation specialist, Weatherford, “There are a number of providers bringing managed pressure drilling technology to the market, and at the end of the day, all of these systems are achieving positive results.”

Arnone compared MPD technology to the early stages of horizontal drilling. The parallel exists in the fact that this technology came at a premium during its infancy, but improved production, increased safety, and lowered overall drilling costs proved this method to be worth the investment. “Simply put, MPD saves time and money and increases safety,” Arnone said. In conventional drilling, parameters often are set at surface. Drilling typically proceeds with little or no change in bottomhole pressure, and any problems that do arise often are mitigated through slight variations in the original well plan. “The old guys tell us, the well talks to you. Conventionally, we need to listen,” Arnone explained.

“The easy wells are gone,” Arnone added. Globally, most new exploration takes place in deep to ultra-deep water where pressures and temperatures can increase risk and have higher rates of failure. “Newer exploration wells are predominantly HP/HT,” Arnone said. Mock well plans from the surface do not always apply to these environments.

HP/HT conditions change the pressure window as fluids come into contact with higher pressures and temperatures . The official point of view on MPD is that these systems precisely control the annular pressure profile, ascertain the downhole pressure, and manage the annular hydraulic pressure profile accordingly. Because MPD operates in a closed-loop system, it provides an additional variable beyond pressure and temperature. The application of back-pressure is applied automatically and can be controlled to mitigate fluctuations in hydrostatic and bottomhole conditions. Arnone discussed Weatherford’s Mass Balance Technique, which uses primary control algorithms to identify influxes and losses on a real-time basis, and it uses a choke at surface to apply back-pressure to maintain well control at all times. The company’s microflow control system is based on measuring flow-in and flow-out of the well. “If flow-in and flow-out diverge, something is wrong,” Arnone said. According to Arnone, the mass balance technique allows a well to be drilled in the “true drilling” window. This may offer a more precise view of drilling conditions compared to a drilling window designed around predicted values. MPD stands out because of its capacity to precisely monitor changing downhole conditions. “MPD can detect flow out differences of one to three gallons, and the lowest ever recorded change was one-quarter of a gallon,” Arnone said. This level of measurement is not possible in a conventional tank system.

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