Investigating the effects of water vaporization on the production of gas condensate reservoirs

Abstract

Well productivity is an important issue in the development of most low and mediumpermeability gas-condensate reservoirs. However, accurate forecasts of productivity can be difficult because of the need to understand and account for the complex processes that occur in the near-well region. When the well pressure falls below the dew-point, a region of high liquid saturation builds up around the well, impairing the flow of gas and reducing the well productivity. It is essential to take account of this condensate-blockage effect when calculating well productivity. Most of the pressure drop in a gas condensate well occurs close to the well walls. Because of the increase in pressure drop and the increase in flow rate, two additional phenomena get involved in gas flow control: The effect of positive coupling (due to increased capillary number) and the effect of inertia (due to non-Darcy flow). In many gas-condensate wells, the final result of these two parameters is improving well productivity, reducing the impairment caused by condensate blockage. Another phenomenon that can take place in high temperature gas reservoir is water vaporization.

Pressure drop near well wall causes molar content of water in gas-phase to increase, therefore connate water starts to vaporize near the well walls. This change in connate water saturation near the well wall can influence well productivity by changing saturation of fluids near well walls. The effect of water vaporization on well productivity of gas and gas - condensate reservoirs are investigated by considering a single well one dimensional radial model simulation. The simulations show that water vaporization increases productivity of well by increasing gas saturation and relative permeability near the well walls and improving the mobility of gas; and this effect is stronger in rich gas condensate reservoir than the lean ones.

Keywords: Well, Gas, Pressure Drop, Vapor pressure of water