Managed pressure drilling (MPD) is a drilling technology applied to unconventional prospects where conventional, hydrostatically over-balanced drilling methods encounter problems. MPD finds its greatest success in drilling plays where the margin between pore pressure and fracture gradient is very narrow. The MPD system constitutes several skids containing manifolds, valves, and sensors that plumb into the drilling rig mud circulating system. This system creates a closed atmosphere in the wellbore, which allows MPD technology to achieve a target equivalent circulating density (ECD) by adjusting surface backpressure across the wellhead. Once the target ECD is reached, stable bottom-hole pressure is established.
MPD allows drilling operations to continue "at balance" in oil and gas plays where primary well control cannot meet the needs of pore pressures due to weak fracture gradients in the well profile. MPD technology provides the required calculated surface backpressure to account for drilling fluid density deficiencies. The system is also able to account for lost annular friction pressure during connections as well as variations in bottom-hole pressure due to surge/swab effects resulting from hoisting operations. In addition to the increase in safety as a result of wellbore stability gained from MPD, well economics improve greatly making managed pressure drilling a highly selectable application.