Predicting Gas Condensate Well Productivity Using Capillary Number and Non-Darcy Effects

Abstract

fax 01-972-952-9435. AbstractThe objective of this work was to provide a more accurate prediction of well and reservoir performance for gas and gas condensate reservoirs by investigating near-wellbore effects. Specifically, the effects of non-Darcy flow and changes in relative permeability due to interfacial tension (1FT), and flow rate (modeled based on capillary number) on well productivity are considered. These effects are shown to be important factors affecting the productivity index (PI) of gas condensate wells. When only non-Darcy effects are considered, the condensate bank can cause an order of magnitude reduction in the PI. Hence, immediate remediation steps might be necessary for formations with high non-Darcy flow coefficients. The reduction in PI with increasing non-Darcy flow coefficient is also highly non-linear. The relative permeability improvement obtained at high capillary numbers on the other hand counteracts the PI reduction due to non-Darcy flow effects. This effect reduces the drop in PI due to condensate buildup and makes the drop in PI more gradual. Hence, both effects should be considered while studying the production performance of a gas condensate reservoir. The capillary -now at ARCO Exploration & Production Technology Co, 285 number effect can in some cases overshadow the two-phase non-Darcy effects. Interestingly, when both non-Darcy and capillary number effects are present, the rate of decrease in the PI at or below the dew point is smaller than the case with the capillary number effect only. A case study of a lean-gas condensate reservoir, similar to the Arun field, was considered and a history match with the production data was performed. Simulation results are presented which clearly show that accurate prediction of PI based on laboratory measurements is possible using both non-Darcy and capillary number effects.

Gas Condensate Damage in Hydraulically Fractured Wells

“…It also have been shown that the productivity index of a gas condensate well is affected by changes in relative permeability due to IFT, gravity and flow rate (modeled based on capillary number). Narayanaswamy et al 39 showed that when capillary number effects are considered, high capillary numbers seen in the near wellbore region can significantly reduce condensate saturation and increase gas relative permeability resulting in productivity greater than when capillary number effects are not considered. They also showed that accurate measurement of the critical condensate saturation and endpoint relative permeabilities at various capillary numbers is very important for accurate prediction of the productivity index.…”

Gas-condensate banking and well deliverability - a comparative study using analytical- and numerical models

“…Because of high flow rates, inertial forces are active in the reservoir, in particular close to the wellbore, where nonDarcy flow are causing an additional draw down pressure drop in the well. Several authors have been studying this problem [11][12][13] where numerical simulations normally are needed to distinguish the physical effects related to two-phase flow and non-Darcy flow.…”

Effect of Non-Darcy Flow on Well Productivity of a Hydraulically Fractured Gas-Condensate Well

“…This model includes the dependence of gas-relative permeability on interfacial tension, pressure gradient and buoyancy forces. Narayanaswamy et al (1999) showed that the condensate saturation and gas-relative permeability near the wellbore are a strong function of the trapping number. They also found that the effects of condensate dropout on gas-relative permeability are closely coupled with non-Darcy effects that can be significant in high-rate wells.…”

“…They also found that the effects of condensate dropout on gas-relative permeability are closely coupled with non-Darcy effects that can be significant in high-rate wells. Narayanaswamy et al (1999) have shown that reservoir heterogeneity plays an important role in determining the effective of non-Darcy flow coefficient for gas inflow into high-rate gas wells.…”