Slugging and Pigging

Slugging and pigging are normal terms commonly used in oil and gas industry, more specifically in upstream rather than downstream. This is mainly because of the different phases of fluid with presence of other materials such as sand. Because of this slugging phenomenon, there is equipment called slug catcher to catch all this nasty stuff by stabilizing the fluids from the reservoir.

In other word, this slug catcher also can be said as stabilizer (some might not agree and it depends how they interpret it) since stabilizing among oil, gas, and water until reaching certain acceptable content level.

This slugging usually takes place when there is either liquid/gas in gas/liquid when form a pocket and starts hitting the wall of the pipe. This at the end actually will shorten the life the piping and causes more frequent maintenance which actually increases the downtime of the plant or platform due to unplanned shutdown. Besides, solids such as sands, wax, and impurities sometime can cause harm to the pipeline which can increase operating cost by increasing pumping cost due to rough surface of the pipeline. So, there must be some alternative need to be taken before the problem exists or during the operation. Slug catcher usually will be installed upstream of the most of unit operation to stabilize the crude to be processed. However, even lot of action has been considered there is also problem persists which end-up with some operational issues such as pressure loss, off-spec products, etc. Once the problems found during the operation then the pipeline need to be rectified.

Pigging is usually a common used method during construction and operation. During construction the pig launcher play a role such that the pigging process can be used for debris removal (onshore and offshore), gauging, measuring, cleaning, flooding for hydro-test, dewatering and drying, and some other specialized applications. During operation the pig launcher is being used for product’s separation (if batch process is carried out for different products), wax removal, line cleaning, condensate clearance, corrosion inhibition, meter proving, and some other specialized applications. So, this pigging is one of method commonly used to prevent, monitor, and rectify any slugging consequences which can cause to the shutdown of the plant/platform.