This paper discusses on the methods of the installation of Corrosion Resistant Alloy (CRA) pipeline for High Pressure High Temperature (HPHT) including its challenges and the subsequent mitigations.
The experience is based on the successful installation of Anjung Gas Development Project which consists of 18" diameter X 8km length of CRA Full Well Stream (FWS) pipeline installed utilizing the (Dynamic Positioning) DP-2 pipelay vessel. The methodology applied in the installation is via typical S-lay utilizing automatic welding system (for the pipelaying) and stalk-on (for the risers at both sides of the platforms). Additionally, Zero Radius Lay (ZRL) method was utilized at buckle triggers. On the existing KAKG-A platform, the riser installation is via suck-in method to avoid removal and reinstatement of the existing riser guard. Two (2) numbers of anode sleds were utilized for cathodic protection. The scope for pre-commissioning performed was flooding the pipeline with fresh water, cleaning, gauging, hydrotesting, air drying, nitrogen purging and packing.
Multiple Concrete Weight Coating (CWC) thicknesses was used to cater for anchoring of pipeline walking. One (1) set of tensioner shoe pads was moulded to suit all CWC thicknesses in order to mitigate the issue of maintaining two (2) tensioners holding the pipeline during pipelaying. The other two (2) tensioners onboard the Main Work Barge (MWB) were installed with sets of tensioner shoe pads suitable for different thickness of CWC. Although with various weld defects experienced, mitigations that were executed proved that the layrate could be improved and finally achieved the target layrate. A wet buckle procedure including its equipments was prepared as a contingency plan. However, due to no wet or dry buckle, this procedure and equipment were not utilized. The project completed successfully with zero Loss Time Injury (LTI) and no major issues. Hence, it is an achievement for PETRONAS. It sets as a standard in moving forward in any new technologies that is developing.
The overall schedule was improved by approximately 20% and cost was reduced by approximately 15% due to the above mitigations. The impact of the successfulness of this pipeline installation is a basis for PETRONAS future CRA pipeline installation as this is the first HPHT CRA pipeline installed by PETRONAS Carigali Sdn. Bhd. (PCSB). This proves one of PETRONAS' 5 Quality Principles, Right Things Right Every Time. The challenges including the mitigations are a good lesson learnt for any future CRA pipeline installation projects that the industry will be undertaking.
In this project, the PETRONAS Technical Standard (PTS) 193004 Installation of Offshore Pipelines and Risers (Amendments/Supplements to ASME B31.8, ASME 31.4 AND DNV OS F101) and API 5LD is the basis for the installation.