Loadout, Transportation, and Installation of the Harmony and Heritage Jackets

Abstract

As an integral part of Exxon's Santa Ynez Unit (SYU) Expansion Project, the Harmony and Heritage platform jackets were loaded out from a fabrication yard in South Korea, transported across the Pacific Ocean, and installed offshore California in water depths of 1200 feet and 1075 feet, respectively (Figure 1). Overall this was a 9-1/2 month effort, beginning with the Harmony jacket load-out in April, 1989 and ending with the Heritage jacket post-installation inspection in February 1990. INTRODUCTION The loadout, transportation, and installation of the Harmony and Heritage jackets were nearly identical for each jacket. Consequently, this paper is structured to present the Harmony jacket, with reference to the Heritage jacket where procedures differed. A timetable of events for each jacket is provided in Figure 2. LOADOUT AND TIEDOWN After fabrication, each jacket was loaded onto an 853 foot long by 206 foot wide by 49 foot deep barge for separate transportation across the Pacific Ocean. This barge, which is the largest launch barge ever built, was capable of safely transporting and launching the Harmony and Heritage jackets. The Harmony jacket was the first to be loaded out. In preparation, bollards and winches were added to the barge to accommodate the loadout mooring arrangement. Further, considerable dredging and excavation was performed to accommodate the 32 foot maximum draft of the barge during loadout. The barge mooring system included six bow anchor lines attached to anchors and four lines at the stern attached to onshore bollards (Figure 3). For the Heritage loadout, only four bow lines were used due to the proximity of the adjacent quay wall. These four lines were tied back directly to the quay wall. The loadout plan was based on the use of the launch barge's 6000 ton jacking system. Once the mooring system was secured and proof-tested, a wire rope link system was installed to connect the barge hydraulic jacking units to pulling lugs on the jacket. In addition to the barge jacks, breakout was assisted by the use of auxiliary jacks mounted on the skidway. Breakout of the jackets required a pulling/pushing force of approximately 6500 tons for Harmony and 5000 tons for Heritage. In both cases this represented a 15% coefficient of static friction between the jacket launch timbers and the land-based skidways. After breakout, jacking forces steadily declined and stabilized at approximately 3300 tons for Harmony and 2000 tons for Heritage, indicating respectively a 7% and 6% coefficient of friction for the remainder of the loadout. Jacket weight compensation and tidal ballasting of the barge were completed using the barge's main ballast system. An independent tidal ballast system was installed for use in the event of failure of the barge system. During the jacket loadout, ballast operations were properly controlled to keep the barge and jacket positions well within the allowable stress envelopes. This was confirmed with dimensional surveys of specific points on the barge and jacket mudline every 15 minutes during the critical loadout phases.