Marine drilling exploration; technical and environmental criteria for rig selection

Abstract

The appropriate rig for offshore drilling is not necessarily the Glomar Challenger of the Discoverer Seven Seas, but rather the combination of equipment that best fits the budget and requirements of the project under consideration. Four categories of drilling and sampling application are discussed: [1] engineering-geological investigations to assess the foundation conditions for large offshore structures. [2] mineral exploration to determine the economic value of potential mining deposits. [3] geological mapping of the ocean floor and [4] petroleum exploration. Within these four major areas, variables are considered that influence the rationale for selection of a particular rig. Selection criteria include sampling, coring and dynamic testing capability, limitying target drilling depths., operating-basis environmental conditions, necessary support vessels and personnel. The tabulations, flow diagrams and discussion of this hierarchy of options are not intended to be exhaustive, but rather to assist the marine scientist in designing a structured decision analysis for selecting the most cost-effective rig for his or her project.