Basic design of subsea BOP stack with RCD for riserless drilling

Abstract

Reelwell Riserless drilling concept has been proposed to overcome the economic challenge of drilling through the thick salt layer. The concept shall bases on RDM method, which is a new drilling method with the concentric drill string other special design tool such as Rotating control devices and Double float valve. The concentric drill string consists of outer conventional pipe joints an inner string specially designed for RDM that shall allow the “return” through the inner pipe. This shall eliminate the need of marine riser, which results in significant cost savings by exclusion of riser related costs and enables us to use smaller rigs with much lower day rate for ultra deep-water drilling operations. There would also be a considerable mud cost reduction and rig space saving as there is no riser to be filled up with drilling mud. The study has reviewed the conventional drilling procedure, the case study's working condition and defined the Basic Design of Subsea BOP stack with Rotating control device for Reelwell-Riserless drilling, to achieve reasonable reliability and performance to mitigate risk in the operation. The BOP control system is also reviewed and proposed a new technology to improve its efficiency in the new working environment.