A Rotational Continuous-Circulation Tool RCCT for Decreasing Non-Productive Time NPT and Mitigating Drilling Operational Risk

Abstract

This work presents how a Rotational Continuous-Circulation Tool (RCCT) can decrease non-productive time and mitigate risks in the oil and gas drilling operations. The proposed tool provides almost continuous rotation of the drill-string and continuous circulation of drilling mud during the making/breaking of drill-pipe connections. Continuous rotation minimizes the stationary time during the connection. Thus, the risk of static contact between the wall of the formation and drill string (which can cause a differentially stuck drill-pipe) is reduced. This is one aspect by which non-productive time (NPT) is reduced, and the potential of encountering a differentially stuck pipe incident is mitigated. Continuous circulation enhances the hole cleaning efficiency. Rather than gravitating or being suspended, drilling cuttings continue to be removed to surface during connections with continuous circulation. As a result, the risk of having a mechanical stuck pipe incident (e.g., Pack-off) is prevented. In addition, maintaining continuous circulation eliminates down-hole pressure fluctuations. This reduces the risk of hole stability issues, and also enables navigation through zones with tight drilling pressure window. The proposed tool has been trial-tested twice to demonstrate its compatibility with the current drilling rigs/practices. Further trial tests are planned to demonstrate the added value of the tool.