Technological Aspects of Shallow Water Drilling

Many of the world’s reserves and potential reserves of hydrocarbons lie beneath the sea, and the oil and gas industry, trying to satisfy the growing demands of the market, during the history has developed technologies and techniques for finding and exploiting hydrocarbons in the often complex and challenging offshore conditions. There are different types of rigs for offshore drilling, some suitable for drilling in shallow waters (less than 500 ft) and others capable of drilling in deep waters (up to 12,000 ft). This thesis focuses on the jack ups, mobile offshore units consisting of a buoyant hull fitted with movable legs that allow the hull to be lifted over the sea level, in such a way to have a stable platform to carry out offshore drilling operations in waters depths up to more than 400 ft. Firstly developed in the 1950s, the jack ups are nowadays the most common type of offshore drilling rig, making up almost 60% of the total fleet operating in the world. Over the course of history, there has been a progressive evolution and development of jack ups which has led to the diversification of designs and technological solutions and that had allowed the units to operate in increasingly deeper waters and in more severe climatic conditions. Technological development has led to increasingly high-performance, efficient, safe and reliable rigs capable to be employed in the creation of increasingly demanding well programs. The creation of this thesis, which lasted more than a year, was derived from the practical experience accumulated during years of work experiences directly onboard the drilling rigs. The experience on different jack ups not only made it possible to collect data and considerations directly gathered in the field but offered the possibility of setting up the work from a practical point of view, favoring the point of view of the drilling contractor, i.e. the company which operates the rigs. This thesis collects considerations regarding all aspects of jack ups, from the study of design evolution throughout the history of drilling, to the study of the market and business peculiarities. Particular attention was reserved to the technological aspects of the jack ups, studying in detail the characteristics of the structural design of the rigs, the interaction between the foundations and the seabed and the details regarding the rig move operations when the unit is moved from an offshore drilling location to another. A case study, directly observed in the field, of a jack up rig move between two offshore well locations is reported accurately, observing in detail all the theoretical and practical aspects from a technical and technological point of view.