Fluid Sampling and Analysis

At VAPS, all experimental work follows documented procedures and instructions.

Sample Validation (Oil and Gas Condensate Systems)

• Bottom Hole Samples: Restored for 24-48 hours at reservoir conditions, checked for water content, opening pressure, and fluid nature. Saturation pressure measured on a sub-sample charged to PVT cell. Duplicate samples should have bubble points within 10-50 psi, and compositional measurement, GOR, and pressured density are determined.
• Separator Liquid Samples: Restored for 12-24 hours at separator conditions, followed by bubble point measurement. Sub-samples used for GOR, compositional analysis, and pressured density. Duplicate samples should have bubble points within 5 psi. Room temperature bubble point can be performed if needed.
• Separator Gas Samples: Restored above separator temperature, opening pressure measured. Compositional analysis performed on sub-sample, including hydrocarbons, carbon dioxide, nitrogen. Hydrogen Sulphide measured externally.

C36+ Composition (Oil and Gas Condensate Systems)

• Bottom Hole Oil Sample or Separator Liquid: Liquid flashed into gas and stable liquid, analyzed separately. Compositions mathematically recombined to give reservoir fluid composition. Major cyclic and aromatic components reported up to C9, beyond C9 reported in carbon number groups. Detailed analysis available, including PNA distribution up to C9+.
• Gas Condensate/Rich Gas Systems: Gas split into gas and liquid phases via cryogenic distillation. Phases analyzed separately and recombined to give full fluid composition. Residual fraction molecular weight and density reported, with a maximum of C100+. Detailed analysis, including PNA distribution up to C9+, available.
• Recombination: Separator samples collected when representative downhole or wellhead samples are not possible. Recombination conducted based on specified GOR or saturation pressure.
• Mathematical Recombination: Reservoir fluid composition calculated by mathematically recombining separator liquid and gas compositions to corrected Gas/Liquid ratio.
• Physical Recombination: Separator oil and gas compositions measured, followed by injection at correct ratio into a recombination cylinder for stabilization.
• Compositional Analysis of Recombined Reservoir Fluid: QA check performed by comparing recombined fluid composition to mathematical data using flash or distillation.

Constant Mass Expansion

• Oil Samples: Charged to high-pressure cell, expanded incrementally through bubble point. Saturation pressure, relative volume, compressibility, and density reported at each pressure step.
• Gas Condensate Samples: Charged to high-pressure visual cell, expanded incrementally to reservoir pressure. Dew point measured, relative volumes provided, and deviation factor Z determined.

Differential Vaporisation/Constant Volume Depletion

• Oil System: Reservoir fluid expanded in incremental pressure steps, evolved gas collected and analyzed. Data reported for each stage, including solution gas-oil ratio, relative volumes, densities, and gas viscosity.
• Gas Condensate System: Reservoir gas depleted in stages, measurements taken of produced gas volume and composition, as well as retrograde liquid accumulation. Viscosity measured using correlations or experimental data.
• Separation Tests: Reservoir fluid subjected to specified separator conditions, measuring gas volume and compositions. Final stage conducted at stock tank conditions for mass balance and overall fluid composition check.

These tests provide information on phase compositions, solution gas-oil ratio, formation volume factor, and stock tank oil density.

• – pH
• – Alkalinity

– Conductivity/Resistivity

– Temperature

– Turbidity

– Suspended Solids

– Particle Count

– Particle Size Distribution

– Compatibility Test

• – Basic ion composition.
• – Tracer Analysis.
• – 27 element analysis.
• – Heavy metal analysis.
• – Isotope ratio 87Sr/86sr.
• – Radioactive isotope analysis .
• – Dissolved ion.
• – Sulphide content,Oil content.
• – Dissolved O2,CO2.
• – Organic Components and acid.
• – Total organic carbon .
• – Aromatics.

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