Types of analyses covered



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Types of analyses covered
Determination of sample composition up to C42+
fluid samples in gaschromatographThe reservoir fluid is flashed in a controlled environment into vapor and liquid components. The resulting fractions are charged to a GC and the resulting chromatograms are processed using Winilab software (for light gases) or Carburane software (for heavier gases and oils). Using PVTlab software, the reservoir fluid composition is mathematically recalculated using the GOR measured during the flash process.
Measurement of Gas Oil Ratios and Formation Volume Factors
In PVT analysis, the flash of reservoir fluid into its vapour and liquid components is done under controlled conditions. A known amount of reservoir fluid at reservoir conditions or other elevated conditions is flashed into liquid and gas components using a flash separator and a gas meter. The gas volume gathered in the gas meter can then be measured together with the liquid volume in the separator and the volume of the original reservoir fluid flashed. Subsequently the GOR and FVF are determined from the above.
Reservoir fluid viscosity measurement from reservoir to atmospheric conditions
A fluid at a working pressure above the reservoir pressure and at reservoir temperature a fluid is charged to a PVT cell and subsequently to an EMV (electromagnetic viscometer) with the absolute viscosity measured at various pressure stages above the saturation pressure. The fluid is then degassed stepwise, with a viscosity measurement at each stages down to stock tank conditions. A final plot of viscosity vs. pressure is generated.
Mole weights and density measurements at ambient conditions
This is done using the cryette and digital densitometer. The resulted data is used in the compositional analysis for the calculation of residue mole weights and densities.
Live density measurement of fluids at reservoir conditions
A fluid at reservoir conditions is charged from a PVT cell to a HP/HT density measuring cell. The temperature is regulated by a thermostatic bath. Measurements can be taken at various temperatures and pressures, recorded, stored and transferred to a computer for further processing
Constant Mass Expansion measurement of bubble and dew points
Constant mass expansion experiment approximates the behavior of black oil and some volatile oil reservoirs. It is used to measure the fluid volume and compressibility over a range of pressures from above the initial reservoir pressure to pressures below the anticipated separator pressures at a constant temperature (usually reservoir temperature). The gas and the liquid phases below the bubble point will stay in equilibrium with the liquid throughout the procedure. This test it is non-destructive. For black oils and volatile oils it is also used to determine the saturation pressure at reservoir conditions. The PV values are plotted. For a black oil or a volatile oil, the transition from single to a two-phase system is easily determined from the plot. For gas condensates the separation of the liquid phase must be determined visually. The client generally determines the number of pressure steps and the working pressure. The CME experiment may also be carried out at other temperatures in addition to the reservoir temperature. The data resulted from the experiment are saturation pressures, relative volumes, compressibility, density at various pressures and reservoir temperature.
Differential Liberation
This analysis is carried out at reservoir temperature to simulate the volumetric and compositional changes in the reservoir during production. The fluid is charged to a cell at reservoir conditions and is expanded stepwise down to atmospheric conditions, with the gas liberated at every step, to simulate the differential mechanism of reservoirs producing oil. The use of PVT cell and the embedded camera allows the operator to control visually the displacement of the gas right to the oil meniscus. Gas volumes, compositions, liquid volume are measured at each step. The oil remaining at reservoir temperature and 0 psig is the residual oil. The residual oil ambient properties (mole weight, density and composition) are subsequently measured. The final data include GOR, Relative Oil Volume, FVF, gas gravity, gas compressibility factor and liquid density.
Constant Volume Depletion
This experiment approximates the behavior of gas condensates fluids. The analysis is carried out for gas condensate and sometimes also for volatile oils, considering the large amount of gas produced and the significant liquid shrinkage. The sample from the previous constant mass expansion is depressurized to the dew point with the volume measured at dew point. Then the pressure is reduced stepwise with the gas removed until the depressurized sample volumes returns to the volume at dew point. At each pressure step, the removed gas and the condensate volume and Z are measured together with the liquid buildup volume in the cell. The fluid produced at each stage can be converted into moles and is used to calculate the fluid remaining in the cell. The final data include the retrograde liquid volume, fluid compositions for every stage, Z, gas viscosity and fluid density.

Separator test
A reservoir fluid is flashed at various pressures and temperatures to simulate the well surface conditions: separator and stock tank. Separator tests are used to predict optimum separator conditions. The fluid at working pressure is charged to the cell or separator unit, and then the pressure and temperature are adjusted to the conditions of the first stage. Once the sample is stable, the gas is removed from the cell. The gas and oil volume remaining in the cell, cell and ambient temperatures and pressures are recorded. The gas composition is measured. The process is repeated at the conditions of the subsequent stages. The last stage reproduces stock tank conditions and the residue of the composition is measured as well.
Physical recombination of separator oil and gas
Based on the separator rates as submitted by the client and adjusted for the laboratory data, such as bubble/dew points, the separator gases and liquids are physically recombined to give the original reservoir fluid. The recombined fluid composition is then measured and the fluid is used for further analysis to simulate the reservoir conditions.

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