Tension Leg Platform Well System Development Overview

ABSTRACT In 1979, Chevron U.S.A. Inc. and its OCS 48 Lease Sale partners, Phillips, Champlin and Impkemix, initiated a project to develop the site specific design for a Tension Leg Platform (TLP) for potential use in producing fields in greater than 1500 feet of water in the Santa Barbara Channel, offshore Southern California. A significant part of this work was the development of a well system suitable for use with a TLP. Most of the work was performed by contractors with Chevron providing overall project management, platform interface control and operational input. Initial concept studies considered both subsea well completions and individual production risers with platform trees. With the selection of individual production risers as the preferred concept extensive analytical studies were performed to determine system dynamic response; component trade-offs were made and a design specification written. Chevron developed system design load cases, and load, stress and fatigue analysis procedures and criteria. This development work culminated in a detailed design and finite element analysis of all load carrying components. In addition, a full scale prototype was manufactured of the production riser tieback connector and its separate tool. This was given a functional and proof-load test INTRODUCTION In /979, Chevron U.S.A. Inc. and its partners, Phillips Petroleum Company, Champlin Petroleum Company, and Impkemix, acquired 22 leases in OCS Lease Sale 48 in the Santa Barbara Channel, offshore Southern California with water depths greater than Isao feet. Chevron U.S. A. Inc., as operator for the group, went to its parent corporation's Offshore Technology and Planning Staff requesting a review of deep water production concepts. This review recommended the use of a Tension Leg Platform (TLP) as the preferred production facility for the design deck load and environment conditions. In order to assess the feasibility of this then novel concept, it was decided to perform a preliminary design of the TLP and all its associated systems. For the unique well system and tendon system, a detailed design was performed. This paper describes Chevron's TLP Well System development effort, just one part of the overall TLP project. In order to determine the feasibility of the TLP concept it was decided to go once through the entire design process. Whenever possible, conventional equipment and technology was to be used. Workable but not necessarily optimized solutions were sought for every design problem. However, in some areas sufficient data was unavailable and had to be developed. The largest development efforts were in the area of analytical procedures to predict the dynamic behavior of the TLP and the risers. These analytical routines were then verified by small scale model tests. Other important developments were done in selecting structural and fatigue analysis criteria, and determining appropriate material fatigue strength levels. For the design project, the TLP was divided into a number of systems, i.e. platform structure, production equipment, tendon system, subsea template, well system.