Detecting Leaks in Purged Pipelines

In 2023, PureHM conducted an emergency inline acoustic leak detection and threat monitoring survey on approximately 9 km (6 mi) of 200-mm (8-in.) carbon steel pipeline that transports crude oil. The operator observed a deviation on their continuous pipeline monitoring (CPM) system, conducted a stand up, and subsequently suspected a leak along this segment. Conventional leak detection methods were unable to pinpoint the location of the suspected leak, and subsequently, the line was purged. Following the purge, PureHM mobilized for an emergency acoustic leak detection and threat monitoring survey. As the leak detection tool required a liquid medium to detect leaks, PureHM collaborated with the operator to prepare a water slug that would function as a carrier for the tool while also providing the liquid medium. The water slug was contained on both ends by cleaning pigs, with the leak detection tool positioned approximately in the middle. The slug and tools were inserted into the pipeline through a standard launcher, traversed the line using nitrogen to push the tool, and were extracted from the pipeline through a standard pig trap. The survey identified three (3) leaks within a 30-m (100-ft) section of the pipeline. The identification of the three (3) leaks allowed the operator to swiftly enact risk mitigation and repair protocols. This paper will detail the process of the inline leak detection survey, the operational challenges and solutions encountered, and implications for future use of leak detection tools in lines without a liquid medium.