One of the main limitations in deep water drilling and drilling in depleted reservoirs is the low margin between the fracture and the pore pressure gradients. Drillstring tripping causes additional pressure variations in the borehole. The use of a Mobile Offshore Drilling Unit (MODU) in deep water results in even more severe surge and swab pressures, which are more difficult to control due to the MODU heave motion. Normally, no control of surge and swab pressure is possible during drillstring connections.

This paper presents the magnitude of surge and swab pressures that can occur in typical drilling operations, but will focus on Through Tubing Rotary Drilling (TTRD) operations. Most of the current methods for Managed Pressure Drilling (MPD) from MODUs do not have a functionality to compensate for both surge and swab pressures. A comparison and evaluation of selected MPD methods for compensation of surge and swab pressure are presented in the paper.

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