How did the gas lift pipeline from a single well come out to the surface? Feel free to discuss and offer suggestions~
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This post was last edited by joseph930 on 2017-10-7 at 10:35. Background: The image shows a gas lift pipeline for a single well; the material used is 20# steel, with dimensions of φ60*7, and the total length is 980 meters. It was installed in 2008 and is entirely buried underground at a depth of 1.0 meter. The soil is Gobi sand, and precipitation is very low； The pressure inside the pipeline is around 10 Mpa, with little variation in pressure; the operating temperature remains stable at around 30°C. This year, it was observed that the pipeline had bulged and protruded above the ground surface. Tests using PCM to determine the burial depth showed that the local burial depth at both ends of the protruding section was also around 0.5 meters. As a result, this pipeline has been taken out of service. The next step is to carry out a comprehensive inspection and dig trenches to restore a burial depth of 1.0 meter. Reflection: 1. Why does it bulge? Thermal expansion? Is it necessary to install thermal expansion bends or similar on such pipes? (I personally think it is mainly due to insufficient burial depth and thermal expansion; however, in similar pipelines that are 5 km long without any expansion devices, no bulging has been observed.) 2. For the inspection of this pipeline, the current approach taken by the inspection agency is a comprehensive inspection. Is it necessary to inspect all welds to verify whether there are any defects? (After all, with so many welds present, the stress on the base material must be considerable.) Welcome to fellow enthusiasts to share their opinions and suggestions; thank you~
Buried pipelines are less affected by external temperatures. Based on the images, it is likely that the valves were opened and closed too quickly or that liquid slugging occurred within the medium. It is recommended to replace the high-pressure pipelines; a 100% RT, 150-kilogram hydrostatic test should be conducted
Dig it up and conduct another test – it’s enough to replace the pipeline
Buried pipelines are less affected by external temperatures. Based on the images, it is likely that the valves were opened and closed too quickly or that liquid slugging occurred within the medium. It is recommended to replace the high-pressure pipelines; a 100% RT, 150-kilogram hydrostatic test should be conducted
It seems to be caused by instability resulting from thermal expansion. The temperature of the pipeline will still change slightly. On top of that, the burial depth is insufficient, and the soil is not adequate to hold the pipes in place. Thus, unstable expansion occurs.