Semi-Analytical Model for Water Vaporization in Gas Producers

摘要

Gas is initially in equilibrium with water at reservoirrnconditions. However, once a well is placed on production, thernpressure drop that occurs around the wellbore causes anrnincrease in the molar content of water in the gas phase. Waterrnwill be vaporized starting from the near wellbore zone wherernthe pressure is small, and form a vaporization front that movesrninto the formation opposing flow. As water is vaporized,rndissolved salts become more concentrated, and eventuallyrnminerals will precipitate into the formation. This might causernproductivity impairment if water continuously suppliesrnminerals to the wellbore area to be precipitated.rnThis study has developed a semi-analytical model tornpredict water vaporization for gas producers. The pseudosteadyrnstate well model solves analytically the pseudopressurernequation and uses the results to explicitly evaluaternwater saturation at each time step. The equilibrium molernfraction of water in the gas phase has been corrected forrncapillary pressure and salinity effects. A modified equilibriumrnconstant has been derived that takes into account capillaryrnpressure.