/community-hubs/measurement-instrumentation/b/flow_weblog/posts/subsea-downhole-casing-pressure-and-temperature-measurementSubsea, or fully-submerged ocean oil & gas equipment, goes back to when “ Shell completed its first subsea well in the Gulf of Mexico in 1961. ” Given the difficulty in accessing this equipment, downhole measurements are essential in maintaining optimumen-USTelligent Community 13