MANAGING GEOHAZARDS IN HARD CONDITIONS: MONITORING AND RISK ASSESSMENT OF PIPELINES THAT CROSSES AMAZONIAN JUNGLES AND THE ANDES

摘要

The hydrocarbon transmission system that belongs to Transportadora de Gas del Peru (TGP), comprise two parallel pipelines: a natural gas (NG) pipeline, which runs from the upstream facilities at Malvinas, in the Amazonian jungle of Cusco-Peru, to a reception station at Lurin (south of Lima); and a natural gas liquid (NGL) pipeline, which transports the condensed liquids from Malvinas to Pisco, on the coast of Peru. The right-of-way (ROW) crosses the Peruvian jungle with both pipelines in its first 200 kilometers, after climbs over the Andes Mountains at an elevation of 4860 masl, and descends steeply toward the coast along the Pacific Ocean. TGP's Pipeline Integrity Management System (PIMS) has identified the Weather and Outside Forces such as main threat which increases the risk of the integrity of its pipelines in jungle and mountains areas. In pipelines with particular characteristics such as pipeline which crosses the Andes and the Amazonian jungle, this threat can cause even a greater number of failures than other threats such as Corrosion or TPD. This threat caused the 70% of the leaks of our NGL pipeline. The geotechnical and geologic conditions were key factors in the risk level of the system since the beginning of the operation. The PIMS of TgP has achieved an important development in the use and suitable handling of the information provided by diverse techniques of pipeline mechanical and the geotechnical inspection and monitoring of the ROW. Different alternative techniques of monitoring have to be taken into account. It is important also to take into account alternative assessment methodologies in order to determine the pipeline exposure, resistance and mitigation to this threat. By integrating these inspections, monitoring and particular assessments as part of PIMS, we have been able get accurate risk assessments in order to mitigate and/or minimize the occurrence of failures. In this way we are able to optimize efforts to preserve the integrity of our system and in addition minimize personal, environmental and business impact. Risk Assessment is an essential part of the Integrity Management System. Our company developed a very comprehensive and detailed Risk Assessment Model based on the guidelines of API 1160 and ASME B31.8S. The probability model is based on logic trees instead indexing models (the most commonly used), that is because we want to reflect in the result all the variables and factors: Exposition, Resistance and Mitigation Factors. By means of the pipeline Integrity Management System developed by TGP, we are able to mitigate risks due to outside forces. We have been able to act before any event becomes critical: TGP NGL pipeline's failure rate due to WOF (number of failures per 1000 kilometers-years) decreases substantially from 5.39 to 1.26 in ten years of operation. For the whole system that rate decreases from 2.33 to 0.46.