A case study of the Severo-Danilovskoye field on experimental and numerical determination of miscibility parameters when justifying gas injection

   Miscibility largely determines the performance of gas injection. Miscible displacement allows achieving maximum effect. The minimum miscibility pressure (MMP) is a key parameter, which is determined when justifying a gas injection project. For the conditions of East Siberian reservoirs, the accuracy of correlation equations is 10-50 %, and A. M. Maklavani, H. M. Sebastian, and M. Dong equations demonstrate the most accurate values. The equation of state matched to the results of routine studies evaluates the MMP with an error of up to 30 %. Additional data from special studies (swell test) increased the estimating accuracy by up to 10 %. An express laboratory method for measuring the miscibility parameter (a method of vanishing interfacial tension) showed high accuracy of MMP estimate. The method also allows describing the process of changing the interfacial tension with increasing pressure or changing the gas composition, and complements the process of adjusting the equation of state when setting up a slim tube experiment.