The technique of drilling a well using the casing string has earned itself a well deserved place as one of the most effective and cost-saving ways to drill and complete a hydrocarbon well; the cornerstone of this is the casing pipe, composed by the pipe body itself and the threaded connection. Normally an API-Buttress type connector is used; nevertheless, it has been proven in both controlled and field conditions that this connector is not completely adequate for Casing Drilling per se, as high torque capacities are demanded. Apart from that, and due to this condition, the constant need for using torque enhancers represents a high limitation to the Drilling with Casing technique itself. For this, Premium-type connectors address this point in a more proper way in form of improved geometries in thread and shoulder profiles and enhanced sealing capabilities.
Despite of this, Premium Connections are seldom used in Casing Drilling applications, being them almost relegated to very special, seldom drilling deployments. However, successful use of Premium Connections in Casing Drilling projects offshore Australia, Norway and onshore Mexico are paving the road for an intensive inclusion of Premium Connections in the field; this has also come as the result of the current diversification of the OCTG market for this connectors coming after a better understanding of load distribution and torque "control" by means of improved geometric design combined with the successful integration of axial-symmetric modeling (Finite Element Method) and Full Scale Testing for design and validation of new couplings. In this work, a holistic approach will address the technological highlights making up the past and current market offer and future tendencies in OCTG specialty connectors for casing drilling, understanding this as the direct result of the evolution of this drilling technique and the recent improvements in Full Scale Testing and computer-assisted design.
It was observed that the drilling of horizontal sections with a casing string in some field developments worldwide was only possible between 1990-2010 due to important modifications made to Full Scale Testing procedures employed to validate newly designed Premium Connections. In this case, the inclusion of a testing stage with bending broadened the usage spectrum in which some Premium Connection geometries were able to perform well; this serves as a concise, yet significative example of the constant evolution the OCTG sector underwent in the last decades, and also a great example of the superb applicability of Premium Connections in high demanding oilfield operations like drilling a well with casing pipe.
This work brings new light into the understanding of the potential of Premium Connections as a standard selection parameter for OCTG used in Casing Drilling, understanding the combined usage both technologies as a clear warrant towards well integrity.