Gas Condensate PVT. The importance of PVT for all aspects of gas condensate engineering can not be over-emphasized. From the estimation of producing condensate-gas ratio, to the impact of condensation on near-well flow and productivity loss, to the potential for enhanced condensate recovery by gas cycling. Whitson provides specialty services impacting all aspects of gas condensate reservoir development.
We can design experimental lab PVT programs for critical discovery wells where every piece of data and information is important to subsequent planning and design of field delineation, initial fluids in place estimation, and basic recovery estimates and simplified modeling. EOS modeling is imperative for gas condensate fluid systems, and we specialize in converting measured PVT data into reliable EOS models that can be used directly, or to create simplified PVT models such as a lumped EOS or black-oil tables. Estimating a gas-oil contact from gas condensate samples is important to mapping the initial fluid in-place uncertainty, and upside potential of an underlying oil zone.
The modeling of condensate blockage is particularly dependent on PVT properties including the expected range of producing CGR, liquid dropout behavior at near-well pressures, and condensate viscosity.
Generally speaking, condensate recovery is low for rich gas condensates – i.e. the more condensate in place, the lower the recovery! Gas cycling of rich gas condensate fluids (e.g. >100 STB/MMscf) is usually considered as an alternative to pure depletion. PVT phase behavior controls the recovery efficiency of miscible and immiscible displacements in the swept volumes of a gas cycling project.
When whitson develops PVT models for a gas condensate reservoir, we take into account all of these relevant issues mentioned above.
Gas Condensate Reservoir Simulation. The impact of condensate blockage and gas cycling efficiency always require reservoir simulation models to quantify cause-and-effect and prioritize development strategies. Both black-oil and EOS reservoir simulators have their place in gas condensate simulation studies, depending on a number of considerations. Developing consistent black-oil tables from a tuned EOS model is necessary to ensure consistency between simulation studies based on black-oil models and simulations based on EOS models. This requires special considerations when generating black-oil PVT tables for gas condensate systems.
Typical reservoir simulation studies that we conduct for clients include:
- Create single-well models from client full-field model to study and quantify condensate blockage.
- Create appropriate sector models from client full-field model to assess enhanced condensate recovery by gas cycling in conventional reservoirs, and huff-n-puff process in tight unconventional reservoirs.
- Implement gas pseudopressure (GPP) methods in client full-field reservoir simulation model to properly account for condensate blockage and well productivity loss. We may study the sensitivity of blockage impact dependent on relative permeability treatment, flow rates, and coarse-grid size.
Condensate Blockage Relative Permeability. Producing wells in gas condensate reservoirs may experience significant loss in well deliverability due to condensate blockage. Collaborating with Stratum Reservoir (Trondheim Laboratory), whitson has, for the past 25 years, designed, managed and interpreted special condensate blockage relative permeability studies. These studies are focused on the objective of describing near-wellbore flow effects and development of relative permeability models that include capillary number and non-Darcy effects. As part of the laboratory program, or as a standalone service, whitson can prepare the developed relative permeability models for use in most numerical reservoir simulators (e.g. ECL100&300 using the Fevang-Whitson pseudopressure GPP option) to match historical performance & study production impairment caused by condensate blockage.
Some projects by whitson on gas condensate reservoir simulation and condensate blockage/relative permeability include:
Whitson has pioneered many gas condensate technologies that are used daily in our industry. We recommend reviewing our relevant publications that are available upon request by clicking here.