Economic Models of Subsea Pipeline Connectors

Abstract

ABSTRACT Economic models analyze the sensitivity of some of the costs encountered in the eleven under sea pipeline connections on the 34" oil line from Ekofisk to Teesside for hydroball/ hydrocouples, hyperbaric chambers, and one-atmosphere chambers. The economic models are summarized by a graph showing the cost for eleven 34 inch connections as a function of the number of productive work days required per. connection. The results do not prove that one system is better than another, but do show the sensitivity to the day rates and productive work days required for each system. INTRODUCTION Economic models analyze one time costs and day rate charges for three systems. The first model involves hydroball/ hydrocouples installed by a lay barge, by the Arctic Surveyor, and by a vessel larger than the Arctic Surveyor. The eleven Ekofisk installations were made from lay barges and the Arctic Surveyor. This experience is utilized by the models. Other costs relate to equipment costs, protective covers, and inspection programs. Costs for installing eleven connections with a hyperbaric system are developed into the second economic model. Costs for burying the splice piece are included. The eleven Ekofiskpipeline connections are assumed to be riser connections to evaluate the one atmosphere chamber system. The equipment costs and other costs of the Lockheed System are modelled. At the time of this writing, the system is not applicable for mid line connections and therefore could only have been used on five of the eleven Ekofisk connections. This lessens the accuracy of the Ekofisk - Lockheed model. THE EKOFISK OIL .AND GAS PIPELINES The huge reserves of oil and gas discovered in the Ekofisk field by the Phillips Norway group in 1969; and later increased by the discovery of six adjoining fields, could only be economically transported by pipeline. This decision has resulted in the construction of two of the largest and longest marine pipelines ever to be built as shown in Figure 1. The large capacity of each line has also required the construction of two intermediate booster platforms on each of the pipelines, believed to be the first ever constructed. Phillips Petroleum Company Norway, operators of the Phillips Norway Group, acting on behalf of the Norpipe A/S, has completed the oil pipeline and is entering the final stages of completion of the gas pipeline. During 1973 and oil and gas pipeline; of this amount, 464 miles were marine pipeline. The 34" o.d. 220 mile oil pipeline from Ekofisk to Teesside, England has a capacity of one million barrels per day and the 36" o.d. 275 mile gas pipeline from Ekofisk to Emden, Germany, has a capacity of 2.28 billion cubic feet per day. Both the oil and gas pipelines are owned by Norpipe A/S a 50-50 joint venture of the Phillips Norway Croup and Statoil, the Norwegian national oil company.