A New Continuous Flow System (CFS) for Managed Pressure Drilling

Abstract

Continuous circulation of drilling fluid offers many benefits, including increased control of downhole pressure in relation to pore and fracture pressures along with enhanced wellbore cleaning. Although the concept of continuous circulation has been known to the industry for a long time, it has gained significance in recent years with real-time downhole pressure monitoring and control. Continuous circulation provides an uninterrupted data stream from downhole sensors and surface equipment even while making a connection, thereby never losing downhole pressure. Weatherford has developed a continuous flow system (CFS), including subs that crown the top of a drillpipe stand and an automated control system that switches mud flow between the top drive and the side flow port. During conventional drilling operations, CFS subs are passive drillstring components. When a new stand needs to be added, a CFS sub connected to a stand already drilled into the well is positioned in the rotary table, and a clamp carrying a side flowline is attached to it. Once the clamp has been securely attached, rig hands can move off the rig floor and conduct the rest of the operation from a remote control panel. At this point, the CFS sub works like a three-way valve. When a sleeve inside the CFS sub is pushed upward, it opens a side flow port on the sub and simultaneously closes an internal valve to cut off flow from the top drive. With concurrent operation of mud valves on a manifold skid, mud flow is redirected from the top drive to the side flow port before breaking the top-drive connection. Mud flow is also directed back to the top drive after adding a stand. The CFS can be used during trip-in and trip-out operations in an almost identical manner. Significant advantages of the CFS are easy implementation into the rig flow loop, automated switching of flow from the standpipe to the side entry port and back from a remote location, high consideration for personnel safety, limited impact on connection time, and a small footprint on the rig floor.

Development of a New Continuous Flow System for Managed Pressure Drilling

“…There are several other similar checks along the way during the flow switching routine. (Cunningham, et al, 2014) Rig tests showed that some practice was required for 2 persons handling the clamp to coordinate their movements. Once they operators became comfortable with the movement of the hydraulic cylinder supporting the clamp they were able to make a connection in a matter of seconds.. Drillers also needed to practice positioning the sub such that side flow port is oriented towards the clamp before setting the slips.…”