Karl Fischer Moisture Analysis for measuring water in crude oil

Measuring the percentage of water in crude oil (BS&W) is an important need in many applications throughout the production and transportation process. It is particularly important in marine and truck custody transfer applications where small inaccuracies can equate to large financial loss.

Traditional methods for both site and laboratory measurement include centrifuge and distillation measurement. However, these methods are slow (between 30 minutes and several hours) and prone to inaccuracies. A company in Houston, Texas called KAM CONTROLS pioneered the usage of Karl Fischer titration to detect moisture in crude oils.

In 1993, a joint standard (API MPMS Chapter 10.9, ASTM D4928, ISO 12937, IP 386) was issued for measuring water in crude oil by coulometric Karl Fischer titration. This method is considerably faster (less than 5 minutes) and more accurate (up to 10 times more accurate than centrifuge and 5 times more accurate than distillation).

How coulometric Karl Fischer titration works

Sample analysis requires 2 reagent solutions: the anolyte (solution in the anode cell) and the catholyte (solution in the cathode cell). A sample is introduced into the anolyte cell which changes the conductivity of the fluid due to added water content, triggering electrolysis.

The time required for electrolysis to complete and conductivity to return to the original level (all water has been removed) can be related to the amount of water in the sample.

Applications for Karl Fischer moisture detection

Karl Fischer units can be used both in the field and in a laboratory. Field measurement is generally used for:

• Well tests
• Water cut meter commissioning, calibration and/or monitoring
• Manual monitoring of water cut

Laboratory tests are used for measurement from samples taken during custody transfer as well as the situations listed above.

Additional applications include measuring water content in gas and various chemicals such as hydrofluoric acid.