Maintaining tight control of bottomhole pressure is critical to successful application of managed pressure drilling (MPD) and underbalanced drilling (UBD) techniques, especially in MPD applications where the window of operation is often significantly narrower than in conventionally drilled wells. Keeping the bottomhole pressure above the pore pressure and wellbore stability thresholds, as well as below the formation fracture gradient, often requires highly accurate control to avoid losses or damage to the wellbore.
The Low Pressure Autochoke Console (LPAC) system from M-I Swaco, a Schlumberger company, is designed for the low surface pressure applications of MPD and UBD and can control casing pressure within a range of ±50 psi. The console has a maximum working pressure of 1,500 psig and a minimum control casing pressure of 100 psig.
A dual console provides independent control systems to simultaneously regulate the set point pressure for two Autochoke units. The console allows the operator to directly set and maintain the desired back pressure on the well. Adjustments to the back pressure can be made via the electronic touch screens on either the local hydraulic power unit (HPU) console or a remote human-machine interface (HMI) panel near the driller.