Technology Update The second of a two-part series, this article presents an update on several managed-pressure drilling (MPD) technologies in use offshore. Approximately one-half of all offshore conventional oil and gas resources are known or thought to be undrillable with conventional, open-to-atmosphere circulating fluids systems for safety, economic, and/or technical reasons. In deeper water, pressure on exposed formations created by a tall column of annulus returns in marine risers grossly overbalances many reservoirs, resulting in a higher proportion of undrillable prospects. Many offshore drilling programs experience a slow rate of penetration and instances of stuck pipe, kicks, and lost circulation, which collectively account for about one-third of all the nonproductive time on drilling projects. As the elapsed time increases, so does the cost per foot drilled and the probability of other things going wrong, creating a temptation for taking short cuts to save time and money. If drilling difficulties lead to the use of excessive casing strings, the result may be reaching total depth with too small a hole for a productive well. An inherent weakness associated with the hydraulics of conventional circulating fluids systems has become more troublesome. In the face of unexpected downhole pressure environments and wellbore instability, the only way to influence the wellbore pressure profile as drilling progresses is to change the circulating rate (mud pump speed), which influences the equivalent mud weight (EMW). The only means of applying backpressure to increase the wellbore pressure profile is to close the blowout preventer (BOP). Consequently, the primary well-control barrier is limited to the hydrostatic pressure applied to exposed formations. The root concepts of the hydraulics of conventional drilling were founded in the Spindletop field in Beaumont, Texas, circa 1901. The “Spindletop gushers” were initially a time of celebration. However, resulting wasted resources, fires, and lawsuits prompted a need to drill into the reservoir without experiencing a blowout. The solution was to drill with weighted fluids, literally mud from a cattle pond at the time. Although drilling fluids technology has come a long way, conventional offshore drilling programs still view the hydraulics of the circulating fluids system essentially the same way— and we still commonly refer to drilling fluid as mud.