Floating-Type Offshore Drilling Vessels

Abstract

After two decades of oil exploration on the world's continental shelf, various design types of mobile drilling rigs have evolved, namely the submersible, the jack-up, and the floater. The authors consider that the current stage of development of these rigs has sufficiently established design patterns which are worthy of investigation and review. The authors have selected the floater type for discussion and presentation as being of germane interest to the naval architect and marine engineer. Section 1 of the paper reviews the design aspects of floating drilling vessels by considering them in two groups: "surface hull" type and "column stabilized" type. Functional design requirements are discussed, including some fundamentals on rotary oil drilling to familiarize the naval architect with its basic techniques. Requirements and recommendations for deck areas and volumes are given, together with representative weights for drilling equipment and vessel weight summaries. Hydrostatic, stability, and motion characteristics are compared between the two types. Structural design, safety features, and logistic support systems are reviewed. Section 2 describes the offshore drilling vessel Reforma as typical of one of the large surface-hull-type rigs incorporating the latest drilling techniques and marine systems. The rig, one of a fleet of three, is owned and operated by Perforadora Mexico, S. A., a private drilling contractor under contract to Petroleos Mexicanos, off the east coast of Mexico.