Continuous Circulation System: a new enabling technology

Abstract

Wellbore problems have existed since the very first oil well was drilled. These problems have cost the oil industry millions of dollars because they lead to substantial loss of valuable rig time, or even loss of the well. Some of these problems are caused by the interruption of the drilling-fluid circulation. This interruption normally occurs when making drillpipe connections. Interruption of circulation causes wellbore problems like ballooning of the well, gelation of drilling mud, and settling of drilled cuttings. It also causes some operating problems in underbalanced drilling. A new technology in drilling has been introduced through a joint industry project to overcome problems caused by interruption of circulation. This technology is the Continuous Circulation System (CCS). The CCS is capable of achieving continuous circulation while making/breaking drillpipe connections. This research highlights the significance of the new technology by investigating the problems caused by interruption of circulation. It presents some potential operational problems regarding the new system and discusses the possibility to achieve continuous drilling. The economics of the new technology is presented. This study found that the CCS would prevent significant wellbore problems from occurring, hence saving valuable rig time and money. It also showed that CCS would be a valuable addition to the equipment used in underbalanced drilling. Continuous drilling while making connections can be achieved using mud-motors. On the other hand, it is not feasible through rotation of the drillstring under the current technology. Finally, the suitable marketing strategy for this phase of the new technology is to offer it for lease rather than for sale.