Changes

The velocity stripping effect is also termed “viscous” stripping due to the effects of viscosity on productivity as explained earlier.  The increase in gas mobility due to velocity stripping occurs as a result of high capillary number. The capillary number (Nc), as defined in Equation 1 below, is the ratio of viscous forces to capillary forces.  

The velocity stripping effect is also termed “viscous” stripping due to the effects of viscosity on productivity as explained earlier.  The increase in gas mobility due to velocity stripping occurs as a result of high capillary number. The capillary number (Nc), as defined in Equation 1 below, is the ratio of viscous forces to capillary forces.  

                      Nc=(v*μ)/σ                        (1)

<math>Nc = \frac{(v * \mu)}{\sigma} \text{  (1)}</math>

 

Where ν is the gas velocity, µ is the gas viscosity, and σ is the interfacial tension between the gas and liquid. As such, with higher velocities and lower interfacial tensions, a high capillary number is obtained and velocity stripping is observed.<ref name=Mottetal_2000>Mott, R., Cable, A., & Spearing, M. (2000). Measurments and Simulation of Inertial and High Capillary Number Flow Phenomena in Gas-Condensate Relative Permeability . SPE Annual Technical Conference Exhibition. Dallas: SPE 62932.</ref>  

Where ν is the gas velocity, µ is the gas viscosity, and σ is the interfacial tension between the gas and liquid. As such, with higher velocities and lower interfacial tensions, a high capillary number is obtained and velocity stripping is observed.<ref name=Mottetal_2000>Mott, R., Cable, A., & Spearing, M. (2000). Measurments and Simulation of Inertial and High Capillary Number Flow Phenomena in Gas-Condensate Relative Permeability . SPE Annual Technical Conference Exhibition. Dallas: SPE 62932.</ref>  

Another effect is also present at high velocities, which acts against the velocity stripping effect. This effect is termed the Inertial (non-Darcy) flow effects, which, at high velocities, reduces effective gas permeability and leads to lower well productivity. On the other hand, velocity stripping increases the relative permeability. However, it has been observed in most gas-condensate wells that relative permeability effects are dominant, hence an increase in productivity is usually observed in these wells.<ref name=Mottetal_2000 />  

Another effect is also present at high velocities, which acts against the velocity stripping effect. This effect is termed the Inertial (non-Darcy) flow effects, which, at high velocities, reduces effective gas permeability and leads to lower well productivity. On the other hand, velocity stripping increases the relative permeability. However, it has been observed in most gas-condensate wells that relative permeability effects are dominant, hence an increase in productivity is usually observed in these wells.<ref name=Mottetal_2000 />

==Well test analysis of condensate banking in gas wells==

==Well test analysis of condensate banking in gas wells==