Analysis of the Effect of Water Flux to a Gas Zone after Through Tubing Perforations on Gas Production by Numerical Simulations

Abstract

After perforating a gas zone with through tubing perforation method, other possible gas zones are also perforated from bottom to top accordingly. However, if one of these zones is highly saturated with water, water might flow through the perforations where gas production is possible. In this study, the water flux from upper perforation to lower perforations where gas is available was simulated by using TOUGH + RealGasBrine simulator. The effects of permeability, pressure differences between zones, and salinity on water flux through gas zone were investigated in this study. Permeability affects the behavior of water flux and its amount to gas zone significantly. Similarly, these effects were seen for the cases with pressure differences between zones and salinity in water zone even though these effects are less than those observed in permeability cases. It was observed that the duration of exposure of gas zone to water flux should be kept minimum by applying well completion operations quickly to isolate water zone and stop water flux from this zone to gas zone. After isolating water zone with well completion operations, gas production simulations from gas zone were conducted at a constant production pressure of 5 MPa. It was observed that gas production from gas zone was retarded and water production from gas zone was higher compared to the original cases without any water invasion. Even in a long term of gas production, it is possible to observe the remarks of previous water flux from upper zone after analyzing water saturation distribution.