The Guyed Tower as a Platform for Integrated Drilling and Production Operations
Authors: Finn Lyle D. , Wardell John B. , Loftin Thomas D. 
Published: December 2007

Design studies and a 3-year, large-scale offshore model test have demonstrated the applicability of a guyed tower as a deepwater drilling and production platform. This paper describes the guyed-tower concept, production platform. This paper describes the guyed-tower concept, presents key results obtained from the field test, and discusses main presents key results obtained from the field test, and discusses main features of the design, fabrication, and installation in 350 m (1,148 ft) of water.

Introduction

Oilfield developments in deeper water will require the introduction of new production systems. The guyed-tower platform concept will extend the water depth limits of bottom-founded drilling and production platforms to at least 600 m (1,968 ft). For water platforms to at least 600 m (1,968 ft). For water depths beyond about 200 m (656 ft), it is anticipated that the guyed tower can provide an economic advantage over fixed platforms that could be significant in justifying development of offshore hydrocarbon reserves. Since the guyed tower permits conventional drilling and production operations, it also can offer advantages over floating production systems that use subsea wellheads. Prototype designs have demonstated that the guyed tower can support integrated drilling and production facilities for single- or twin-rig drilling operations and production rates in excess of 100,000 B/D (15 900 m3/d). Drilling operations are conducted from the deck of the tower, and conventional field processing equipment and utilities are in modules on a two- or three-level deck. Crude oil could be transported to market through a pipeline; however, in deepwater operations an pipeline; however, in deepwater operations an offshore terminal may be used to transport oil to market.

Guyed-Tower Concept

The guyed-tower concept illustrated in Fig. 1 is "compliant" in that it moves slightly in response to the applied wave forces rather than rigidly resisting the applied loads like a conventional platform. The tower is held upright by several guylines that run through swiveling fairleads to clump weights on the ocean floor. The lines extend from the clump weights to pile anchors or conventional drag anchors. Under normal operating conditions the tower deck motion virtually will be imperceptible. During a severe storm the weights lift off bottom, permitting the tower and guylines to absorb the environmental loads. Because the guylines are attached to the structure near the water surface, the tower is supported laterally near the center of the applied environmental forces. As a result, large overturning moments are not transmitted through the structure to the base, a disadvantage of the conventional pile-founded platform. The guyed tower rests on a vertical bearing foundation called a spud can. Well conductors penetrate the spud can and flex slightly as the tower pivots.The guyed tower is an ideal structural concept for deepwater applications. This can be illustrated by considering the two factors: large foundation requirements and dynamic amplification of wave forces, which dramatically increase the cost of fixed platforms as water depth increases. platforms as water depth increases. JPT

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