Owing to the soil profiles in most of Vietnam's projected site, Reverse Circulation Drill Method is considered to be the most suitable and economical construction method for the pile construction. Combined, all MPD riser stack components should be automatically controlled by a central intelligent control unit responding to the unique wellbore signals being monitored, including return flow, to enable immediate detection of changes in fluid flow.
For this application, the Model 7875 BTR RCD is installed above the intermediate riser joint and below a standard slip joint about 140 casing rotator ft below the rig floor and roughly 40 ft below sea level. RCD rigs are applied to drilling large diameter holes (1,000-4,000 mm).
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.
In the view of Derrick Lewis, global operations manager at Halliburton business line Geobalance Measured Pressured Drilling Service, MPD offers considerable benefits in terms of an additional barrier with the RCD, the ability to mitigate lost circulation and well-control incidents, and the ability to tell if the well is taking an influx or ballooning, as well as an increase in rate of penetration (ROP), which is generally experienced with MPD.
The installation of a few minor components in the MPD riser stack and rig surface equipment, enabled the rig to rapidly transition from open to atmosphere with RGH” to full MPD capability thus providing a step change in the rig's capabilities - a transition process that saved 12-14 months rig up time.
Fully realizing MPD benefits in deepwater applications requires a focused industry effort to develop guidelines, procedures and standards for equipment procurement, rig modification and design and perhaps most importantly adequate training for rig personnel.
The overall drilling costs can actually be reduced by up to 40% when using RCD, safety and requires fewer man hours, requires less water than other method. Managed Pressure Drilling (MPD) provides ability to control and finely tune Bottom Hole Pressure (BHP) by introducing and controlling backpressure of wellbore returns.
Reverse Circulation Drilling (RCD) in Soil had been widely used for Bore Pile construction. This will help many in the industry to implement and design such innovative techniques and robust equipment for the mitigating drilling hazards. In this chapter, after a brief outline of the floating drilling equipment and subsea systems, the riser components and vessel data are outlined.