312 km Mubadala Ruby Field Subsea Gas Pipeline Dent Investigation and Assessment

Abstract

Mubadala Petroleum (pipeline operator) responded to a pig stuck in a 312 km subsea gas pipeline. A bi-di pig was found to be stuck and after being rescued, the bi-di pig discs were found to be dented. An investigation and assessment are conducted to found what causes pig stuck, to solve the issue of a pig stuck, and to execute all the processes during pipeline operation as effectively and safest way as possible. The investigation started by defining what makes dented bi-di pigs, is an object inside the pipeline or pipeline deformation. A series of conformity techniques are applied by calculation to predict exact pig stuck location, using the backpressure method. A series of inspections were conducted from simple to complex way. From a smart pig that resulted from pig damage to side-scan sonar (SSS) inspection, and visual inspection at predicted location due to cost and time limit. The result is the investigation and assessment process to find dent location within 312 km seabed are executed in a time effective and cost reduced way, under 2 years for all activity for technical process and field execution duration. The sequence also escalating from lowest cost and easiest methods (engineering calculation) to the highest and more complex methods and cost (inspection and survey). The accurate result of prediction confirmed by the dent location and damages at KP 111.89 and 30 meters water depth. The investigation methodology also complies with the requirement of regulation, company specs, standard/code, and engineering best practices. The benefits of this paper are as a reference to conduct series of pipeline damage investigations for a long-distance and remote subsea pipeline. The investigation sequence can apply to many cases with accurate prediction to reduce investigation cost, time, complexity, and risk.