Summary
Crude Oil Quality Association
Water Measurement Subcommittee
New Orleans , LA
January 29, 2004  

ASTM Crude Oil Crosscheck - Harry Giles of the US DOE presented data from  ASTM’s crude oil interlaboratory crosscheck program via a table comparing D4006 (Water in Crude Oils by Distillation) and D4928 (Water in Crude Oils by Coulometric Karl Fischer Titration).  The summarized data (mean and standard deviation) indicate that more water is found when using Karl Fischer and that the test method is more precise.  Please note that samples are not analyzed in duplicate and there is no assurance the participating laboratories followed the test method as written.  Harry did note that the latest round (not included in the data presented) seems to be indicating more water from the distillation method.  However, the precision is still less and the percentage of water found is at the lower end of the range included in the scope of the Karl Fischer test.  Harry will update the group with data from the latest test, as available. 

It is important to note that the crude oils utilized in the crosscheck program are of medium gravity with sulfur content from 0.1% to 2%.  The type of crude did not seem to cause a discernable difference between the two test results.  Harry asked COQA members to consider providing crude from their supply for the crosscheck program and got a few volunteers.  We also discussed the possibility of adding a centrifuge method to the crosscheck program.  Currently, BS&W by centrifuge is the method most widely used by pipelines.  Having centrifuge data in a usable format and in significant volume from the crosscheck program could lend credibility to the stand that Karl Fischer (which can be used in a field test) is more accurate and precise.  Some COQA members who are active in the ASTM agreed to bring up the question.  

ASTM CROSSCHECK DATA - View this Document******
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Online Water Measurement Technology – Mr. Chip Westaby of Agar Corporation presented the basics of water cut technology.  Sampling, Capacitance, Density, Microwave and Optical are all methods used to determine the amount of water in a crude oil.  Agar’s latest technology utilizes microwaves.  This works on the premise that organics do not absorb microwaves.  All technologies / methods of water measurement can be affected by the density and viscosity of the oil, the salinity of the water and the velocity or temperature of the flowing oil / water mix.  However, Agar’s latest generation of testing equipment is not affected by or corrects for these.  There are certain criteria required to achieve good test results.  There needs to be well mixed flow (for example, after a static mixer or pump) and the sample needs to be taken form the middle of the pipe.  Also, gas in the mixture will affect the results.  With the compensations, test results are within +/ - 0.01%.  Agar has found that the sulfur content of the oil can also be detrimental to accurate readings.  They do know the degree to which sulfur can affect the test results and the next generation of inline water measurement will undoubtedly correct for sulfur along with salinity, density, temperature, etc.

INLINE WATER MEASUREMENT - AGAR CORP. - View this Document******
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