Automatic system reduces response times to influxes or losses, minimizes influx size, optimizes circulation rates and increases drilling speed. Compared with a typical surface application where the RCD sits atop the BOP and requires only a bottom flange to bolt it to the stack, integration with a riser system above a subsea BOP required a new RCD design that could be connected at the bottom and the top.
As the water depth increases, integrity of drilling risers is a critical issue. Circulation Drilling (RCD”) with optimized airlift is a proven method for Pile Top casing tube RCD drill rigs. This can provide instantaneous detection and response enabling drilling decisions to be made before they escalate to an uncontrollable level.

Unlike the slow processes of circulating a column of modified density mud into the wellbore (as would be performed in conventional drilling systems) the backpressure imparted by MPD equipment is transmitted through the entire fluid column in seconds to counteract influxes or losses.
MPD is a ten-year-old technology that keeps drilling pressure at, or slightly above, reservoir pressure, which, it is argued, in most circumstances gives better control of the annular pressure profile throughout the wellbore than under-balanced or over-balanced techniques, where the pressure is maintained below or above that in the reservoir.
Rcd is the rotary circulating device which is used in underbalanced drilling( when bottom hole circulation pressure is lower than formation pressure being drilled) which allows drill string reciprocating and rotary motion in the closed BOP situation.

A typical land-based MPD operation might represent 10-20% of the overall well cost, he says - at the lower end if it is not implemented through the entire well section, and also depending on whether it is a directional or straight hole, and using oil or water-based fluids.
It is normally used on wells drilled from floating rigs (semi-submersible or drillship) using a subsea BOP. So, the snub drilling spread will usually have a smaller footprint than a conventional drilling rig. Pressurized mud cap drilling (PMCD), which can be used to drill formations where total circulation losses make conventional circulatory methods impossible.
The R.C.D. (Reverse Circulation Drill Method) method is one of the typical large-scale cast-in-place concrete pile construction methods. Interchangeable drill bits are specifically engineered to suit different rock types and vein widths. A workover riser is typically used in place of a drilling riser to reenter the well through the subsea tree and may also be used to install the subsea tree.