Water cut for crude oil refers to the mass percentage of water in all the liquids, i.e. crude oil plus water. Water cut is an important parameter along with the ‘Gas to Oil Ratio’ (GOR) of a crude oil to clearly indicate the water content in reservoir fluids.
Water cut can be expressed using following equation,
Water cut = Mass of water in a sample X 100 / (mass of water + mass of oil in the same sample)
Water cut is usually expressed in percentage. Water cut for crude oil flowing in a pipeline can be measured using water cut meters. Water cut meters are typically used in the mineral oil industry to measure the water cut of oil flowing from a well, produced oil from a separator, crude oil transfer in pipelines and in loading tankers. There are several technologies used. The main technologies are dielectric measurements using radio or microwave frequency.