Summary
In late July 2003, for the first time since rotary drilling was introduced, a section of hole was drilled without interrupting circulation while new joints of drillpipe were added to the drillstring. This was made possible by the use of the continuous-circulation system (CCS), developed over the previous 3 years by a joint industry project (JIP) that was managed by Maris Intl. and funded by six major oil companies (Shell U.K., BP, Statoil, BG, Total, and Eni),Coupler Development Ltd., and Varco, and supported by the U.K.'s Industry Technology Facilitator. The field trial of the CCS was carried out on a land well being drilled in Oklahoma, U.S.A. Its success marked the end of the JIP and the commencement of commercial development of the system.
The CCS is a new and enabling technology; the potential benefits of which include the following:
Elimination of negative and positive pressure surges when stopping and starting circulation to make a connection.
No rig downtime to circulate out cuttings to clear the bottomhole assembly before making a connection.
Improved drilling-fluid management.
Elimination of kicks on connections.
Improved control of equivalent circulation density (ECD).
Reduced total connection time (TCT).
Reduced chance of stuck pipe during a connection.
No downtime in high-pressure/high-temperature (HP/HT) wells to circulate out connection gas.
Reduced wellbore "breathing" or "ballooning."
Improved safety around the rig floor.
Potential applications of the system include the following:
Extended-reach drilling (ERD) and horizontal wells.
HP/HT wells.
Near or underbalance wells.
Deepwater wells.
The CCS is also a potential-enabling technology in achieving the "one-tripwell."1 The concept was presented in a paper by inventor L. Ayling at the Offshore Technology Conference, May 2002.2
