BS&W: Basic Sediment and Water
Basic sediment and water (BS&W, BSW or Watercut) is a measurement of impurities in liquid hydrocarbons such as crude oil. Raw crude oil will contain some amount of water and particulate matter from the reservoir formation. The BS&W of a fluid hydrocarbon measures free water, sediment, and oil emulsion as a volume percentage.
Water Content in Oil Recovery
Manual Watercut measurement is decreasing in some applications in favour of on-line water determination (OWD). On-line water determination measures the water content of fluid only. Sediment is not measured in OWD though it is common industry practice to consider OWD and BSW synonymous. Water content can be measured with a water cut meter at various stages of the oil & gas value chain, from the wellhead to refined product custody transfer.
The water content of reservoir fluid can vary greatly from field to field, and may be present in large quantities for older fields, or if oil extraction is enhanced using water injection technology. Most water and sediment is separated out in the field at the production site to minimize the quantity that needs to be transported via pipeline to refining facilities. The residual content of these unwanted impurities is measured as BS&W as the product leaves the production facility. Monitoring sediment and water content is accomplished by manual sample testing methods and/or automated on-line devices.
BS&W in Crude Oil Custody Transfer
Sales contracts of unrefined oil may specify a BS&W limit to ensure the fluid entering the process is within acceptable quality limits. If the BS&W is not controlled before reaching a refinery, the refiner may include initial quality improvement processes such as dehydration and desalting. A Watercut meter is used to ensure the crude oil is of an acceptable quality for the refining process. The maximum water content in crude oil Custody Transfer applications is typically 0.5%.