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.

Developments in OCTG connections defining well integrity and mechanical performance of oilfield tubulars are not something newas a continuous feedback between field challenges and theinnovative nature of the Industry is something derivated into newer, more intensive Full Scale Testing procedures and novel analytic tools for connection performance evaluation in the last decades. The relationship between all those factors has been condensed in the present paper which gives shape to a comprehensive "technical history" for Premium Connections, hidden and scattered so far in issued patents, manufacturer manuals, brochures and selected field cases generated between 1935 and 2017. Design schools can be well defined by manufacturer and region;apart from this, theadvancements in testing and manufacturing made possible to adjust the connection to the technical constraints put fromthe field, namely a high need for gas tightness and enhanced torque capabilities. Last but not least, it was discovered that, among all oilfield equipment used during upstream operations, it was (next to advancements inSSSV's)the constant evolution of tubular connectiontechnologieswhat contributed to "crystallize" the modern concept of Well Integrity, especially after the big offshoredevelopments seen from 1971 on. As a corollary, the impact of current standardization protocols ISO 13679 / API 5C5 on well integrity in terms of metallic seal integrity will be assessed in the light of the tribological and mechanical evolution of the MTM seal during testing and validation.

Over the last 30 years, Coiled Tubing (CT) has become one of the most important tool for wellbore interventions, completions and even drilling. The success of this technology lies in its high degree of flexibility which is based on the conscious destruction of its own working material – the Coiled Tubing itself – caused by low cycle fatigue. The current standards and best practices for the fatigue simulation are based on testing frames that are as old as the coiled tubing itself. In a working environment such as the oil and gas industry, where safety of operation is a key parameter, a reliable fatigue model that allows to track the fatigue damage and to stop using a pipe before it breaks becomes critical. Therefore, this paper provides a discussion of the existing fatigue testing setups and an inside of the prediction models. The second part of the paper will focus on discussing the true loads of a coiled tubing used for drilling applications. Finally a newly built for purpose testing facility is presented, showing the latest developments in accurate testing of coiled tubing used for deep drilling applications. The experimental tests have shown a good compatibility with existing testing setups, but the new added capabilities exceed the actual performance, and allow the development of a new coiled tubing fatigue prediction model.