There are an abundance of reasons why regular pigging is advantageous - from cleaning out debris, water or oil, to executing preventative or corrective maintenance to ensure the integrity of a pipeline.
Pigging is also often used in the pre-comissioning or decommissioning phases of a pipeline to prepare the line to receive oil or gas by removing the pre commissioning fluid (usually water) and replacing it with gas or glycol based fluids, or in the case of decommissioning, cleaning the line of hydrocarbons and debris to allow it to be decommissioned.
However with these benefits come an array of challenges associated with both mechanical and foam pigs, which are the most commonly used types, that can result in costly problems or prevent pigging from happening at all.