Continuous Circulation Drill String Sub

Abstract There is an increasing need to drill difficult reservoirs in a cost effective way. Over the past few years Managed Pressure Drilling (MPD) has made it possible to drill reservoirs which have a narrow window between pore and fracture pressure gradients. Before the introduction of MPD techniques, safely drilling and completing these formations was very costly and not always successful. Cycling the mud pumps off and on for connections affects the pressure and is a major problem for MPD. Techniques and equipment have been developed to make a connection while continuing to circulate the drilling mud to maintain constant pressure. Since 2005, the Continuous Circulation System (CCS) has allowed continuous circulation during connections with traditional jointed drill pipe, by using a chamber around the connection. Several companies have developed continuous circulation subs which are threaded between tool joints to achieve continuous circulation without a pressure chamber. These have had varying degrees of success from both an operational and safety standpoint. This paper describes the current MPD market and describes the philosophy adopted for a new side-entry sub.