Platform Emmy Strengthening And Requalification
Authors: Kallaby Joseph , Digre K.A. , Eskijian M.L. 
Published: October 2008

Older platforms that may require assessment and/or strengthening to continue operation are of primary interest and concern to operators, designers and regulators. Experience with damage assessment and abatement, evaluation of the strength of damaged members and the evaluation of the capacity of strengthened members are subjects of equal interest. The experience with platform Emmy adds to this emerging pool of knowledge.

Platform Emmy was installed offshore Southern California in 1961, using design guidelines and practice current at the time, both of which have undergone drastic changes. The platform suffered both cracks and member indentations, due predominantly to accidental impact by equipment and a supply boat. The present operator used various methods to reduce the operational and environmental loads on the one hand, and to increase the resistance of the platform structure on the other. These were performed in order to continue platform operation and to obtain requalification permits, The operator used novel techniques based on recent tests to evaluate the strength of damaged members, and also used unique approaches to damage control, containment and monitoring. The criteria used for reanalysis are presented. The need for appropriate criteria is discussed. The involvement of the regulator and third party reviewer is also presented.

HISTORICAL BACKGROUND

In 1961, Platform Emmy was installed in 45.5 feet of water on California State Lease PRC 425.1, Huntington Beach Offshore Field, approximately one mile offshore Huntington Beach, California (Figure 1). The original owners operated the platform as a drilling and production platform.

A satellite platform was added in 1980, south of Emmy, connected by two personnel bridges. The satellite housed equipment and supplies on a single deck for a steam-water flooding program (Figure 2).

Shell purchased both platforms in 1986 from Phillips Petroleum, the owner at the time. They are operated by Shell Western Exploration and Production, Inc. (SWEPI). An initial survey was conducted which revealed damage at the -3 bracing level; subsequently, both platforms were included in a comprehensive survey and upgrade. Since no significant damage was observed on the Satellite Platform, only Emmy is reviewed in this paper.

An original set of structural drawings was available, indicating the structural framing, sizing and detailing, as well as the pile foundations [1]. A typical broadside (east) elevation, as originally designed, is shown in Figure 3. Similarly, a narrowside (north) elevation is shown in Figure 4. The original soil investigation report was also available [2]. The platform was designed to Uniform Building Code (UBC) criteria, current at the time. These criteria were later incorporated into the First Edition of API RP2A in 1969, but were replaced by modern seismic guidelines in the 7th Edition, 1976.

PLATFORM DESCRIPTION

Emmy is comprised of a three-level deck, a jacket and a pile foundation. The deck is an open frame with X bracing along both main axes to accommodate lateral loads. It consists of two girders running north-south and seven trussed girders running east-west. The Drilling Deck supports the workover rig, a mezzanine is located above the Production Deck and the Lower Deck houses utility equipment