Gas condensate flow around deviated and horizontal wells

Drilling deviated and highly deviated wells (DWs) in gas condensate reservoirs is aimed at increasing reservoir reach and reducing pressure drop, thus improving well deliverability. The flow of gas and condensate around the wellbore when the pressure drops below dew point pressure is affected by phase changes and variation of relative permeability (kr) with velocity and interfacial tension (IFT). Flow simulations and well productivity calculations for these near critical fluid systems and in the case of such three dimensional DW geometries, are more complex compared to those of a 1D radial vertical well. There are limited sensitivity studies dedicated to such important petroleum engineering situations.

We have developed various mathematical single-well models simulating flow of gas and condensate around such wells. A comprehensive sensitivity study (over 500 simulation runs) was then conducted to evaluate the impact of pertinent parameters on the DWs performance with some important practical findings. We have also considered horizontal wells, which are DWs with the deviation angle of 900. The results demonstrated that the performance of DWs strongly depends on wellbore gas fractional flow (GTRw) and velocity. For instance, for a given pressure drawdown, the coupling effect (increase in kr due to an increase in velocity or decrease in IFT), improves the performance of highly DWs at short well lengths, whilst the negative impact of high velocity inertia (a decrease in kr by an increase in velocity) is more pronounced at higher GTRw, smaller wellbore radius and higher reservoir thickness values. For long DWs the productivity ratio (deviated to vertical well fluid production rate ratio) does not vary with GTRw. However, for short DWs, it increases for moderate condensate fluid but decreases for the rich gas condensate fluid. This is due to the variation of contribution of coupling and inertia with GTRw in the deviated and vertical wells.