Research on a Computational Method for Reservoir Pressure of a Water-Drive Condensate Gas Reservoir

Reservoir pressure of condensate gas reservoir is an indispensable parameter for calculation of gas reserves, gas well productivity evaluation, dynamic analysis, and evaluation of anticondensate. The water-drive condensate gas reservoir is ranked among the most complex types during development. In the development process, reservoir pressure declines, condensate oil dropouts, and content of water vapor in condensate gas increases, while edge water invades continuously, thus accurate calculation and prediction of reservoir pressure is particularly difficult and important. Calculation of retrograde gas condensate influenced by porous media adsorption and capillary pressure, and water vapor content in condensate gas tested under different pressure, according to material balance principle, material balance equation of water-drive condensate gas reservoir is established by consideration of absorption in porous media, capillary pressure and water vapor as well, and finally reservoir pressure at any time during production could be computed by iteration. Case study shows that the reservoir pressure calculated by this method gets much closer to actual reservoir pressure and it finally shrinks the workload in field testing and brings more convenience to scientific research and production management.