Abstract

It has been identified that neoprene coated risers of large gas pipelines, expose continually manned platforms to high safety risks. The neoprene is susceptible to impact damage and due to peeling, corrosion may occur along the edges of the coating. Available alternatives to reduce those risks are for instance: to terminate those gas pipelines at a separate riser platform, or to install riser fenders in combination with improvements to the riser splash zone coating. Monel has been used in some instances in the oil industry as an alternative to neoprene as riser coating. In these cases the Monel was applied as sheeting; however inspection of the riser by ultra-sonic means was not possible because of the gap between the Monel sheets and riser pipe. This paper addresses the possibility of continually bonding the Monel onto the riser pipe by means of hot rolling, thereby maintaining the ability to inspect the risers with ultra-sonic means. However this production process has some areas of concern: in particular, iron contamination of the Monel reduces its corrosion resistance in sea water. This paper reports on the trials that were conducted to quantify the above problem associated with iron contamination and a solution is provided.

Introduction

Petronas Carigali Sdn Bhd, in a production sharing contract with Sarawak Shell Bhd, is the operator of the Baram Delta oil and gas fields, which are located off the coast of northern Sarawak, Malaysia (refer to fig. 1). Currently new platforms and pipelines are being installed under the Baram Delta Gas Gathering scheme (BARDEGG) to collect the associated gas produced in five of these fields for domestic consumption and export (reference 1.). In the BARDEGG scheme the new Baronia BNG-B gas compression platform plays a pivotal role (refer to fig 2). The platform receives gas from various fields in Baram Delta through a number of pipelines. The gas is treated and dehydrated at BNG-B, compressed and exported to the MLNG Plant in Bintulu via the E11 platform in Central Luconia. Export to E11 is through an 18 inch 125 km long pipeline. During a safety assessment study conducted for the BNG-B platform it was recognised that the gas inventory of this platform is considerable, given the fact that the platform is connected to quite a number of gas pipelines. Complexity of platform operations requires the platform to be permanently manned. Hence if a gas pipeline riser would fail, a major accident would occur. A tragic example is Piper Alpha, where the failure of the gas pipeline riser generated a fire ball engulfing the entire platform. The most likely causes of pipeline riser failure are due to corrosion or impact. In Baram Delta the new gas risers are protected in the splash zone with fenders and neoprene is used as anti-corrosion coating.

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