In the push to resuscitate aging fields and tackle more hazardous pressure conditions the value of new pressure drilling technology can be measured by its impact on drillability. One new technology has proved effective at solving real world pressure stability problems and redefining what is economically drillable. Two recent applications are cited to illustrate the innovative manner in which it enabled one operator to achieve an industry first in a deepwater depleted GOM field and another to achieve an industry first in a deepwater shallow gas field in Myanmar.

The automated Dynamic Annular Pressure Control (DAPC) system is designed to continuously control the bottomhole pressure (BHP) throughout the drilling operation, with the rig pumps on or off. It consists of a choke manifold, a backpressure pump, and an integrated pressure manager. Automation is easy to claim, many pressure management systems do. But the feature of the DAPC system that supports its claim lies within its pressure manager – a network of high speed, safety critical, control software and hardware designed to maintain the BHP at a fixed setpoint pressure.

In pressure drilling the BHP must not fluctuate beyond desired safe limits at the setpoint. The integrated pressure manager’s ability to minimize fluctuations within a small window is a direct function of its speed and accuracy. Its speed is a function of the speed at which the model calculates BHP – once a second – and at which it can adjust the choke – fractions of a second. Its accuracy is driven by the accuracy of the model which is calibrated to the downhole measured BHP every time it gets pressure while drilling (PWD) data.

Benefiting from the integration of data, software control, and hydraulics analysis two operators in widely different applications achieved industry firsts by controlling BHP at new levels of speed and accuracy.

In on-going drilling efforts to redevelop mature deepwater GOM fields Shell discovered reduced reservoir pressure and fracture gradient in intervals that still required original mud weights for borehole stability. Based on previous wells drilled with the DAPC system Shell won the first government approved use of static underbalanced mud in deepwater. By reducing the static mud weight below pore pressure Shell reduced the equivalent circulating density, eliminated previously unmanageable lost circulation, reached targets too difficult with conventional methods, and effectively extended the life of their mature fields.

In their plans to explore the shallow gas Nagar prospect offshore Myanmar’s southern coast Petronas searched for a solution to manage a number of potentially high risk scenarios. Their search led them to develop an industry first solution designed around the automated DAPC system. By using wired drill pipe to transmit high speed, real-time PWD data directly to the pressure manager they utilized the full potential of the DAPC system to detect kicks quickly, accurately control BHP during the kick, and simultaneously circulate out the gas. In simulated nitrogen kicks on the rig the system proved it could control pressure with the speed and accuracy needed to safely drill Nagar.