Repair methods for damaged pipeline beyond diving depth

Abstract

Mechanical damage of a subsea pipeline is found as one of the most severe concern in management of pipeline integrity. The need to reach and bring the hydrocarbons from the fields located in deep and ultra-deep waters, imposes the need to improve the technologies and techniques in order to repair any unacceptable damage in pipeline. The main objective of this work is to investigate various methods for repairing a subsea pipeline that has been damaged and that is below diving depth. The investigation covers the methods that are applicable for three different water depths of 150, 350 and 1350 meters, two different pipe sizes of 12 and 28 inches and two different length of lines: 5 km (e.g. in-field pipeline) and 500 km (e.g. export pipeline). Since the cause and severity of damage determines the necessity and type of required repair, it is significant to study different scenarios of damage: dent, crack (field joint) and corrosion. For this purpose, the studies and investigations that have been performed so far will be reviewed. Welding sleeves and mechanical couplings provide the main solutions for major damages. High pressure and structural clamps are also repair tools for minor damages. Remote welding concept is under development for deep waters .The repair challenges have been discussed and some ideas are concluded. The idea of Angled-clamp that is presented in this project can be developed for the damaged angled pipes and for spool connection where alignment is hard to achieve.