Abstract

Offshore Oil export, being a batch process, is required to be at the highest loading rate possible to lift off the continuously produced oil and also to shorten the loading period of ships, so as to improve the time to market. But at the same time, it needs to be managed in the safest manner, as any operational error or a bad weather could cause a big oil spillage and pollute the marine environment significantly. This calls for a bigger offshore infrastructure, with large size and lengthy submarine pipelines all the way to the deep draft area of the sea to enable bigger ship to berth and a higher pumping rate with fail safe control system.

KOC started offshore crude oil export in year 1969, with the commissioning of Sea Island terminal located 10 miles offshore. It had a 48″ dia. Crude oil Submarine line and a 20″ bunker submarine line. The control system for emergency shutdown was provided with a surge relief system and a relief collection vessel at the sea Island platform. After 10 years, in 1979, a new single point mooring (SPM) terminal was added with surge relief collection vessels and the submarine lines were extended from Sea Island further 3KMs to connect with SPM. In year 1996, two new single buoy moorings (SBMs) were built and the same old submarine line was further extended 3 KMs each to connect with both SBMs. In year 2008, the complete offshore system was re-built with new offshore infrastructure as detailed under.

The present new offshore infrastructure consists of four (4) nos. of single buoy moorings (SBMs) of catering anchor leg mooring (CALM) type, each with a dedicated 56" dia. submarine pipeline of length over 20KMs, so as to cater the biggest range of oil tankers in the world. The crude oil loading rate could be over 100,000 bbls/hr simultaneously in each of the four CALM buoys. For bunker service to the crude oil ships, a bunker loading system consisting 20″ & 24″ submarine pipelines are also in place, to meet a maximum loading rate of 1000 Mt/hr for fueling the ship. The offshore loading terminal of SBM type, is a floating buoy without any permanent structure and is remotely controlled from an on-shore control room. The ship is moored to the buoy on a single point, so that it could move- weathervane - around the terminal. In the event of ship moving away from the terminal due to very bad weather or any other reasons, the crude/ bunker loading to the ship would be stopped automatically by a breakaway mechanism on the hoses. This would result in high surge pressure in the loading system and the weakest link, which is the loading hose, would be protected by isolating the same from the upstream by sudden automatic closing subsea valve (PLEM) together with emergency shutting of on-shore export pump.

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