Ever increasing costs associated with drilling operations in a hostile marine environment dictate that the ratio of actual drilling time to total time expended be increased to the greatest possible limit consistent with safety. This paper discusses equipment, materials, procedures, and personnel required to fully utilize capabilities of new generation semisubmersible rigs in achieving this goal during year-round drilling operations in deeper water in adverse environments. Criteria established for selecting basic equipment and innovative items are outlined. Procedures and auxiliary components needed to assure compatibility of subsystems and the effect of new concepts on primary drilling objectives are reviewed. Responses to the problems of resupply and support, measures conceived to promote timely and advantageous use of specific skills of all personnel and benefits resulting from shallow marine studies are presented.
High cost of deep water drilling in a hostile environment demands the greatest possible effectiveness of all equipment and personnel. Daily costs for operating and supporting one of the new semisubmersible rigs total about $50,000. Costs are not expected to decline and will no doubt exhibit further increases as deeper water in the more open reaches of the sea is challenged. Employing inadequate equipment with an apparent savings in daily rental cost has long been recognized as false economy. The operator therefore has little recourse other than to accept greater costs. But conditions in higher latitudes of the North Sea, in the Gulf of Alaska, off Canada and in other offshore areas around the world are such that the best drilling rigs and supporting units will continue to be subjected to long periods of rough weather during which little, if any, productive work can be performed. Since all costs are ultimately borne by the operator, the operator has a great incentive to accomplish more productive work in less time than here to fore but without incurring greater per well costs.
Two complementary approaches can be made to obtaining more productive work which, from the operator's viewpoint, can be defined as the actions directly connected with drilling hole and evaluating horizons penetrated by the bit. First, the ratio of time spent in productive work to total rig time can be increased to the greatest limit consistent with safety. Second, the most optimum procedures can be formulated and implemented for all phases of the operation. The first approach requires investment in equipment to supplement the minimum with which the drilling goal could be reached if total time and total costs were of little importance. Even though most drilling contractors provide somewhat more than minimum equipment, in the context of this paper, basic equipment in the context of this paper, basic equipment refers to the minimum.
