Pipeline operators regularly run pigs for various applications, such as cleaning, batching, and integrity inspections. These runs are often completed without the aid of transmitters or pig tracking, making it difficult and problematic to pinpoint the location of a pig if it happens to get stuck in the pipeline.
This paper will discuss recent research and advancements in locating stuck pigs using a non-intrusive technique with a technology known as large standoff magnetometry (LSM). Additionally, the influence that operational and pipeline conditions, operating factors, and technical calculations have on the process will be deliberated; likewise, the collection and analysis method, and future developments will be presented. Finally, a case study from a recent project will present the cost-effectiveness, process efficiency, operating procedures, and reduced environmental impact of the LSM technique when compared to standard methods of identifying the location of a stuck pig.
Pigs are currently available in varying size and type and are run in pipelines for a wide variety of applications. The common types deployed into pipelines are cleaning pigs, batch pigs, purge pigs, and smart pigs which are also called inline inspection (ILI) tools. There are substantial costs involved in an integrity assessment completed using pigs, these costs are from the overall inspection, throughput loss due to pump or compressor station bypass, and tracking. The factors that influence the success of a pig run are pipe cleanliness, fluid medium, flow rate, pressure, temperature, speed of the product, and total run time.1 Pig tracking plays a crucial role in a pig run as it aids in controlling some of the success factors and the overall inspection cost. When pig tracking is used during pig runs a pipeline operator is provided with the following information: near real-time location of the tool, estimated time of arrival (ETA) to above ground references (AGR) or critical sites along the line, and estimated pig velocity. This information aids pipeline operators in efficiently planning pump or compressor station bypassing which minimizes throughput loss, reduces operational risk, and increase revenue.2 Some pipeline operators use an alternative method referred to as "batch tracking" to approximate the pig's location during a pig run, this is accomplished using pump rate and product throughput information.1 This method is not conducive for knowing the precise location of a pig, communicating ETAs to downstream sites, monitoring the pig's near real-time velocity, and efficiently bypassing pump or compressor stations. Batch tracking is commonly used during short runs or runs involving cleaning or batch pigs. When pig tracking is not used there have been instances where pigs have been stuck, lost, or have damaged valves at stations. In the absence of pig tracking there is an improved and cost-effective methodology to identify stuck pigs or obstructions in a pipeline by using large standoff magnetometry (LSM) technology.
