API Exploration & Production Standards Winter Meeting Fort Worth , January 26th, 2011

Testing Heavy BrinesAPI 13 J – ISO DIS 13503-3

Hydrometers & Density measurements

Bernard Fraboulet, TOTAL Technology Specialists

Density & specific gravity measurements

Hydrometers Density hydrometer

• Concept : mass per unit of volume (ρ) • SI Graduations in g/ml - kg/m3 • USC Graduations in ppg • Reference temperatures

– SI 20°C – USC : 70°C ( 21.1°C)

Relative density (specific gravity) hydrometer• Concept : ratio of ρ sample by ρ water at the same temperature• Graduation dimensionless • Reference temperature 15.56°C /60°F• Ratio of sample density to water density at 60°F : 999,012 kg/m3 ≡ 0, 999 012 g/ml (8,337 ppg)

Hydrometer and normative references

ISO 387: 1977 Principles of construction and adjustment ISO 649:1981 Density hydrometer for general purposes

• part 1 : Specifications• Part 2 : Test methods and use

for both part : no adoption by USA

ISO 650 :1977 Relative density 60/60°F hydrometers for general purposes Not adoption by France and Germany and then by CEN

Reference & Reporting temperature ISO 387 Reference temperature

• Clause 4.1 - density hydrometer : − 20 °C (68°F) − In special circumstances : substitution to 15°C (59°F) or 27°C (80.6°F)

− 27°C i.e 80°F recommended − other reference temperatures ? USA : 70 °F ?

• Clause 4.2 : relative density hydrometer − 60°F ( 15,56°C) for liquid and water

Density reporting temperature For any measurement done at a temperature which is not the reference one, a

correction is required. General reporting : when density hydrometer is used why to report at a different

temperature than the reference ’s one ? Does it need to get a direct conversion between SI ref. temperature to USC’s (20°C

– 68°F) or between USC ref. temperature to SI’s (70°F – 21°C) ?

• Reporting temperature proposal : • SI report : 20°C • USC report : 70°F • Left to users

Clause 6.2.1 Hydrometer description

• More accurate description • As per ISO’s : class M100 hydrometer• 6.2.1.1 Density hydrometer• 6.2.2.1 Relative density hydrometer

• Calibration :• at least quarterly

Temperature Correction factor

• Density hydrometer • Only a correction linked to hydrometer volumetric change

is required : − Standard glass thermal volume expansion 20 x 10-6 − Table linked to readings and temperature − Minor difference lower than uncertainty if the same table is

used for 20°C or 70°F as reference temperature− Two tables ( SI and USC) possible

Temperature Correction factor

• Relative density hydrometer• Reference temperature 60°F • Correction whatever the reporting temperature • Correction linked to

− Glass volumetric change − Water temperature density variation

Correction factor : − Complex equation − tables of coefficient − variations as per author/references

Proposed changes• Clause 6.4.1 Temperature correction for hydrometer

– 6.4.1.1 Density hydrometer• Correction factor (unit kg/m3 or 10-3 g/ml)

– 6.4.1.2 Relative density hydrometer• sub clause 6.4.1

– no changes – Add SI equations