Development of a numerical algorithm for volumetric evaluation of retrograde reservoirs with data scarcity

Abstract

Characterization of gas condensate (retrograde) reservoirs requires determining the in-situ fluid composition for accurate reserve calculation. Traditionally, in the absence of complete PVT studies in mature or marginal fields, graphical correlations (Rzasa & Katz, Standing) are used; however, these are susceptible to human reading error and hinder automation. This work presents the development and validation of a numerical algorithm that digitizes such correlations, allowing for the rapid volumetric evaluation of Original Gas in Place (OGIP) and associated condensates. The methodology integrates polynomial fitting equations and pseudocritical property correlations into a computational workflow. The algorithm was validated through case studies, showing a deviation of less than 3.05% compared to the standard graphical method. The proposed tool facilitates agile reserve re-evaluation in data-scarce scenarios, eliminating the subjectivity of visual interpretation.