Calsep can offer support designing a fluid sampling and a PVT laboratory program.
Factors influencing the design are:
- Fluid type
- Reservoir pressure and temperature
- Production strategy to be applied
- Likely presence of asphaltenes
Sampling and QC of Samples
PVT experiments performed on reservoir fluids are costly and often used to make decisions about production strategy as well as in reserve estimations. For these reasons it is important that the fluid sample is representative of the reservoir fluid. Calsep can advise on what type of sample to take, i.e. whether a bottom hole or separator sample is the more appropriate for the actual type of fluid. Calsep may further advise on the well conditioning required to take a representative sample and on the sample volume needed to conduct various types of experimental PVT studies.
When a sample and fluid composition exist Calsep can carry out a series of Quality Checks. If certain tests fail, Calsep will be able to recommend whether the fluid composition can be corrected and used for EoS modeling purposes or must be discarded.
Routine PVT Study
Calsep can advise on the extent of a routine PVT study, which will usually cover the below or a subset of the below experiments:
- Constant Mass Expansion (CME)
- Separator Tests
- Differential Liberation
- Constant Volume Depletion
- Viscosity experiment
It is important that a separator test is designed to provide information about the fluid behavior at the pressure and temperature conditions in the process plant. The remaining experiments are usually carried out at the reservoir temperature and CME tests also sometimes at 1-2 lower temperatures.
PVT Studies for Enhanced Oil Recovery (EOR)
EOR PVT studies are to be carried out when gas injection EOR is considered. The below figure shows a schematic drawing of a typical EOR PVT study. Calsep can help design the EOR experiments (swelling, equilibrium contact, slimtube and multi-contact). When the experiments are conducted, Calsep may assist interpreting and quality checking the data.
Flow chart EOR PVT study
Asphaltenes may form as the result of natural depletion or initiated by gas injection. If asphaltenes precipitation is not taken into account during a routine or EOR PVT study, it may severely affect and even ruin the measured data. Calsep can advise on whether asphaltene precipitation is likely to take place as a result of natural depletion or initiated by gas injection. Calsep can help you design an asphaltene study that will reveal whether asphaltene problems can be expected during production and Calsep will design the experiment in such way that they are suited to create an asphaltene EoS model.
Shaikh, J.A. and Sah, P., Experimental PVT data needed to develop EOS model for EOR projects, SPE-144023, EORC, Kuala Lumpur, Malaysia. July 19-21, 2011.