In a broad sense, rigs can be categorized as immobile and mobile. These terms describe the ability of the rig to depart quickly from a drillsite if necessary. This categorization is broad and provides little definition on each rig type. Land and marine classifications provide a more logical grouping for rig types....
Managed Pressure Drilling Definition & Applications 
Managed Pressure Drilling (MPD) is an adaptive drilling process used to precisely control the annular pressure profile throughout the wellbore. The objectives are to ascertain the downhole pressure environment limits and to manage the annular hydraulic pressure profile accordingly. The intention of MPD is to avoid the continuous influx of...