Glass Hydrometer Method (ASTM D-1298)
- For stabilized hydrocarbon sample (preferred method)
- ASTM D-1298
- Stabilized liquid hydrocarbon sample is cooled to approximately 15°C or 60°F (depending on the liquid pour point) and transferred into a hydrometer jar.
- Find observed density and temperature
- Correct observed density to 15°C – as per ASTM D1250 Table 53.
- Glass hydrometer and thermometer shall be certified by legal (authorized) governing body.
Digital Density Meter Method
- For stabilized hydrocarbon sample
- A known volume of liquid sample is introduced into an oscillating sample tube.
- The change in the oscillating frequency caused by the change in the mass of the tube is used in conjunction with the calibrated date to determine the density of sample.
- Convert to @ 15°C
- Equipment shall be certified by legal (authorized) governing body.
Water Fisher Titration Standards
- ASTM D-4377 : Karl Fisher Titration
- ASTM D-4928 : Coulometric Karl Fisher
The sediment content in the sample
- analysed in accordance to membrane filtration or by extraction method;
- must be added to water determined by this method to obtained total BS&W content.
Known mass of homogenized liquid sample is injected into the Karl Fisher analytical instrument and tiltrated to an electromagnetic end point to determine the mass% of water.
The Karl Fisher instrument used shall be calibrated against sample on a mutually agreed frequency.
BS&W Analysis by Centrifuge
- ASTM D-4007 : Using heated centrifuge
- ASTM D-1796 : Non-heated centrifuge
Equal volumes of samples and solvent (water saturated toluene) are placed into a cone-shaped graduated centrifuge tube.
After centrifuging, the volume of the higher gravity BS&W layer @ the bottom of the tube is read.
Reading shall be reported as BS&W in volume%.
BS&W Analysis by Membrane Filtration
The sediment content in the sample analyzed by this method must be added to the water determined by Fisher Titration/distillation to obtained the total BS&W content.
A portion of a representative crude oil samples is dissolved in hot toluene and filtered under the vacuum through a 0.45 micron porosity membrane filter.
The filter with residue is washed, dried and weighted to give the final sediment content in weight %.
The mass of residue, calculated as a % is reported as sediment by extraction.
Determination of moisture in live crude
By Coulometric Karl Fisher method. The water content is determine using ASTM D-4928.
- Unstabilized crude
- the pressurized sample is homogenized by shuttling the internal piston back and forth by applying a pressure different.
- Then, a representation sub-sample is removed from the receiver using a pressure syringe via the septum port.
Categories: Oil & Gas Notes