Keith B. Wilson

Phase Equilibrium Considerations in Using Nitrogen for Improved Recovery From Retrograde Condensate Reservoirs

The increasing value and limited availability of natural gas has made its use for conventional cycling economically unattractive for most condensate reservoirs. Nitrogen is a relatively inexpensive and plentiful gas. The phase behavior of both lean natural gas and nitrogen were investigated in static, equilibrium mixing tests. These tests indicate that mixing of rich condensate with either lean natural gas or nitrogen will cause an increase in dew point. The increase in dew point resulting from mixing with nitrogen is much greater than that resulting from mixing with lean gas. However, packed column displacement tests indicate that very little mixing occurs as either gas displaces condensate from porous media. This leads to the conclusion that nitrogen is an effective displacing gas for condensate reservoir cycling. (10 refs.)