Managed Pressure Drilling has gained widespread popularity and a great deal of press coverage in recent years. By applying MPD techniques, it is possible to drill holes that simultaneously expose formations with pore pressures very close to the frac pressures of other exposed formations with minimal formation influx or mud losses. Complex and expensive systems have been designed and implemented to maintain pressure on the wellbore using hydraulics modeling software, automated chokes, and continuous surface circulating systems, often working in conjunction with each other. These systems usually require several specially trained operators. This aggregation of personnel and equipment increases both the footprint and housing required for implementation, as well as substantially increasing the cost of the operation.

MPD replaces the pressure exerted by static mud weight with dynamic friction pressure to maintain control of the well without losing returns. The objective of the technique is to maintain wellbore pressure between the pore pressure of the highest pressured formation and the frac pressure of the weakest. This is usually done by drilling with a mud weight whose hydrostatic gradient is less than what is required to balance the highest pore pressure, with the difference made up using dynamic friction while circulating. That sounds quite simple but has been made extremely complicated.

The big problem is maintaining constant wellbore pressure while transitioning between circulating with little or no annular pressure and shut-in with proper annular pressure to maintain balance. A great deal of time and money has gone into trying to do this with no change in wellbore pressure throughout the process. Field experience has shown that this is not necessarily cost effective, demanding an answer to the question, "Is all this complexity really necessary?" The answer in many cases is "No."

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