Navigating BS&W or Water-in-Oil Measurement in the Oil Industry: A Glossary of Key Terms by XSENS

Water-in-Oil Measurement terminology:

In the Oil and Petroleum Industry, accurate measurement of water content in oil (also called BS&W or Water Cut measurement) is critical for quality control and operational efficiency. Many terms exist to address this topic and it can get confusing even for the most experienced in this field. XSENS provides the below terminology overview associated with water-in-oil measurement to help clarify commonly used terms in the industry. Let’s look into some of these crucial terms, ensuring you’re equipped to navigate the different terms related to water measurement in oil.

Water Cut:

Water Cut is a fundamental metric representing the percentage of water content in an oil sample, for example measuring a range of 0-100% Water Cut in oil. Understanding and monitoring Water Cut is crucial for maintaining product quality and adhering to industry standards. The term Water Cut is typically used when trying to improve Test Separator operations, to improve flow rates from wells, to measure water content in Custody Transfer or Fiscal measurements, or to generally increase operational efficiency. XSENS offers a clamp-on non-intrusive ultrasonic type Water Cut Meter with an accuracy of +/-1% absolute over the full range of 0-100% Water Cut. We measure the Water Cut by measuring the Speed of Sound (SoS) of the liquids with online measurement. Read more about this product here: XACT Water Cut.

Below are similar terms that are often used to describes a mixture of water in oil.

BS&W (Basic Sediment & Water):

BS&W denotes the combined measurement of sediment and water content in crude oil. It is a critical factor in determining the purity of the oil and its suitability for processing. This term is often used in request for quotations from our clients, who are looking for a BS&W Analyzer, or inline BS&W measurement, to measure anywhere from 0% to 100% Water Cut. XSENS offers a clamp-on non-intrusive ultrasonic type Water Cut Meter with an accuracy of +/-1% absolute over the full range of 0-100% BS&W or Water Cut. Read more about this product here: XACT Water Cut.

Water Liquid Ratio (WLR):

The term WLR or Water Liquid Ratio quantifies the proportion of water to the overall liquid content in a petroleum sample. Accurate measurement of the Water Liquid Ratio aids in process optimization and quality assurance. It is typically used when talking about Water Cut or BS&W measurement. XSENS offers a clamp-on non-intrusive ultrasonic type Water Cut Meter with an accuracy of +/-1% absolute over the full range of 0-100% BS&W or Water Cut. Read more about this product here: XACT Water Cut.

Oil-in-Water (OIW):

OIW or Oil-in-Water refers to the presence of oil droplets in water. Monitoring OIW levels is essential for environmental compliance and ensuring efficient oil-water separation processes. Often this term is used to measure parts-per-million (PPM) of oil droplets in water and indicates that the required OIW Oil-in-Water technology has to be very accurate and sensitive to measure at PPM level. XSENS does not provide this type of equipment.

Dissolved Water:

Dissolved Water refers to water molecules that are fully integrated into the petroleum product. Precise measurement of dissolved water content is vital for assessing product stability and quality. XSENS can measure the amount of Dissolved Water with our XACT Water Cut meter in the range of 0-100% Water Cut or BS&W.


An Emulsion is a stable mixture of oil and water that does not readily separate. Monitoring emulsion levels is crucial for ensuring efficient separation processes and preventing pipeline issues. XSENS can measure the amount of Emulsion with our XACT Water Cut meter in the range of 0-100% Water Cut or BS&W.

Entrained Water:

Entrained Water is water suspended in oil, excluding emulsions. Proper detection and measurement of entrained water are essential for maintaining product quality and preventing equipment damage. XSENS can measure the amount of Entrained Water with our XACT Water Cut meter in the range of 0-100% Water Cut or BS&W.

Free Water:

Free Water exists as a separate phase in oil. Detecting and measuring free water content is crucial for ensuring product purity and preventing issues during transportation and processing. XSENS can measure the amount of Free Water with our XACT Water Cut meter in the range of 0-100% Water Cut or BS&W.

Homogeneous Flow:

Homogeneous Flow occurs when the liquid composition is consistent at all points within a container, tank, or pipeline cross-section. XSENS does not necessarily need a homogeneous flow for accurate water cut measurement. For other technologies  however, maintaining a homogeneous flow is essential for accurate water cut measurement. To ensure homogeneous flow, other vendors require installation of a statix mixer upstream of their meter, which adds cost and complexity to on-line water cut measurement. XSENS does not require installation of such a mixer which saves significant project and installation costs for our clients.

Fluid Velocity Profile:

The Fluid Velocity Profile represents the distribution of fluid velocity across a pipeline. Understanding and optimizing this profile is crucial for efficient oil-water separation processes and accurate water content measurement. XSENS can identify the fluid velocity profile due to our patented and unique helical shaped transducers. Watch the product video’s here which explains how our technology is able to do this.

Dry Oil:

Dry Oil refers to oil that is free from water content. Monitoring and maintaining dry oil is essential for preventing corrosion and ensuring the longevity of equipment. XSENS measures the speed of sound of a sample of dry oil and of water during installation of our meter. This ensures correct reading of our water cut meter when water is entering the oil, as this will significantly change the speed of sound of the oil and water mixture.

Oil and Water Sampling:

Accurate Oil and Water Sampling involves extracting representative portions from a total volume for analysis. Precise sampling is crucial for obtaining reliable data on water content and other parameters. Sampling can be done manually, by taking a sample in a bottle from an extraction point on the pipeline. It can also be done automatically by Sampling Systems, to have more accurate and timely samples. The samples are then taken to a laboratory for analysis of the content of the sample. One of the measured components is BS&W which is used as the indication of Water Cut, or water-in-oil in the liquid. These samples often have a lower accuracy than water cut meters, as many external factors can influence the sample.

Oil-Water Separation:

Oil-Water Separation is a critical process in the industry aimed at removing water from oil. Efficient separation is essential for maintaining product quality and preventing equipment damage. To ensure the separation process is efficient, a water cut meter is installed on the oil outlet of a Production or Test Separator. This is a perfect spot for our XACT Water Cut meter which can measure real-time 0-100% water cut.

Sample Loop, Analyzer Loop:

A Sample Loop is a low-volume stream diverted from the main pipeline for analysis. An Analyzer Loop is dedicated to analytical instruments, ensuring accurate and continuous monitoring of water content. To measure BS&W or Water Cut on large pipelines (typically 8″ or higher), some type of inline meters are installed in such by-bass loops as they can not be produced in such large sizes. It could also be that a by-pass loop increases the flow rate which is needed for several types of inline meter to provide accurate measurement. For the XSENS XACT Water Cut meter, such by-pass loops are not required, as we can easily measure on pipe sizes ranging from 2″ to 36″ and even higher. Our meter can also measure water cut from as little as 0,1 m/s fluid velocity, providing accurate water cut measurement even when the water and oil are separating at such low flow.

Stream Conditioning, Static Mixing, Flow Conditioning:

Stream Conditioning involves distributing and dispersing pipeline contents for accurate sampling. Static Mixing and Flow Conditioning utilize devices to achieve proper mixing and conditioning of the flowing stream, enhancing the accuracy of water measurement. Many inline type meters need a Homogeneous Flow to ensure accurate water cut measurement. In such cases, some kind of mixing and flow conditioning will be applied by installing inline mixers or conditioners. This adds extra cost, maintenance and complexity to a project. XSENS typically doesn’t need devices to be installed for mixing or conditioning the flow to measure water cut. Our technology is therefore very straight forward to be installed: let XSENS install our water cut meter on the outside of the line and it will do the job without need of extra equipment.

Upstream Straight Length, Downstream Straight Length:

These terms refer to the straight sections of pipeline required upstream and downstream of a measurement point. Adequate lengths are needed for achieving a stable flow profile and accurate water content measurement with traditional inline meters. The XSENS technology however has proven to be providing high accuracy measurement even with 2.5 times the diameter of a pipe straight length after a 90 degree bend. Please read this Whitepaper where our technology was tested on 2.5D, 5D and 10D straight length. Other inline technologies often need anywhere from 10D to 20D upstream and/or downstream straight length, making it cumbersome to install.

XSENS Water Cut measurement with clamp-on technology