The integrity of drill string while drilling especially under dynamic conditions plays a very crucial role in efficiency; reaching the target (pay zone) and even economical aspects. Considering the dynamics of drill string one would immediately think of vibrations; particularly torsional vibrations, posed on drill string. In worst cases the phenomenon of stick/slip occurs, in which the bit comes to a full stop and then accelerates uncontrollably. The non-uniform acceleration and deceleration of RPM continues to exist during drilling operation with possible catastrophic consequences. Bringing the bit off the bottom and adjusting the RPM are the conventional approaches which are performed on the surface. This paper reviews and analyzes the present solution approach as related to drill string torsional prevention measures. Furthermore, a proactive solution would be proposed in contrary to the existing methods to prevent the occurrence of torsional vibration in both vertical and directional wells drilled with top-drive system, which will be performed downhole. By rotating the drill string at top, it stores energy along itself. At a particular point in time drill string accelerates and rotates in an uncontrollable manner due to act of friction and spiral spring behavior of the drill string. During this process the stored potential energy in drill string is converted to kinetic energy. The proposed approach entails the use of hydraulic power to prevent storing the potential energy along the drill string. That is, if there is an acceptable maximum level of stored potential energy, conversion into kinetic energy will not happen. By this means, the torsional vibrations are highly mitigated if not eliminated completely. The proactive solution seeks prevention of a phenomenon (torsional vibrations) which can lead to calamities if not contained. However, efficient drilling and ROP are chief goals of drilling engineers. Also this proactive solution will be done down the hole not on the surface. Hence, more efficient drilling is sought by preventing one of most disastrous incidents.
Well Integrity is one of the most critical topics concerning the E&P sector nowadays, especially during the development of unconventional hydrocarbon resources. Among them, the exploitation of natural gas from shale and hydrocarbons from deepwater reservoirs pose considerable challenges to the entire well system, specifically in one of its more critical elements: the threaded connection. In the current state of the art, Premium Connections are the best option for ensuring wellbore integrity and mechanical reliability. Despite of its proven improved capabilities compared with standard API Casing connectors, Premium Connections are still relegated to "special applications". In the case of offshore drilling, and in the light of new drilling techniques to develop deepwater resources, the use of Premium Connections to drill with casing tubulars offshore Australia has demonstrated the great opportunity this type of connection has for deepwater developments. In this work, a brief historical overview will be given addressing the technological highlights that contributed to the current market offer of OCTG specialty connectors for unconventional oil and gas applications. By means of a comparative, however, detailed analysis of available geometric profiles on the market in the last 15 years (ie. improved dovetail thread, coupling bevel, toroidal sealing surfaces, etc.) and the current state of the art of applicable norms, standards and their validation levels (Connection Application Level (CAL)) it was concluded that an additional improvement on the mechanical reliability of the connection still can be achieved. This would be noticeable in form of gas-tighter connections as per ISO 13679 and bigger torque capabilities (e.g. for casing drilling) during make and break operations. Parallel to this, a new definition for "well integrity" is provided considering the role threaded connections play as critical innate safety barriers within the wellbore system; an extensive discussion on historical development of Premium Connections is provided, focusing in the innovations that took place in the last 15 years in OCTG for Shale Gas applications and Deepwater Drilling, at the same time the current state of the art of norms and standards for OCTG is critically cited.
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