Summary of Nitrogen Miscibility with Oil For Gas Displacement Recovery

With today s Socioeconomic climate, reserve growth from already discovered fields is again a key industry<br>focus. An important approach to enhanced oil recovery (EOR) reserve growth is gas displacement<br>recovery (GDR) with nitrogen. N2 GDR projects around the world today are currently injecting over 1.8<br>billion standard cubic feet per day (BSCF/d). The methods applied have included: immiscible<br>displacement, pressure maintenance in oil reservoir gas caps and condensate gas reservoirs, gravity<br>drainage, N2 as a driving agent for a cushion gas, and miscible displacement.<br>The implementation of a miscible displacement project depends on engineering with the N2 - oil<br>Minimum Miscible displacement Pressure (MMP) property. In this study we review and summarize the<br>state of knowledge for determining N2 - oil MMP. Past published laboratory work has been summarized<br>and compared. This includes the influences on MMP and the variability in estimation. For simulation<br>equation of state (EOS) approaches have also been summarized, variably described, and best practices<br>noted.<br>Laboratory measured MMP data displays considerable variability and is affected by oil composition and<br>reservoir conditions. This paper summarizes the state of our current N2 miscibility knowledge, exploring<br>the effects of fluid and reservoir conditions.