A procedure for appraisal of a hydrocarbon reservoir continuity and quantification of its heterogeneity

Abstract

Quantification of the heterogeneity in a hydrocarbon reservoir, which is crucial during different production phases, could be performed using qualitative and semi-quantitative data such as analysis of reservoir sedimentology, stratigraphy, reservoir architecture, measurement of physical and geochemical properties of the hydrocarbons and formation waters. In this study, strontium isotope residual salt analysis (Sr-RSA) method is used to examine possible reservoir compartmentalization in a Permo–Triassic carbonate reservoir, in Persian Gulf. Different Permo–Triassic units in the studied field show heterogeneity in lithology that is reflected in reservoir compartmentalization. Detailed profiles of 87Sr/ 86Sr ratio of residual salts show two main different reservoirs down the studied well, i. e., upper and lower reservoirs. Moreover, the upper reservoir shows some Sr-heterogeneity that indicates small scale compartmentalization. The isotopic composition of formation waters from different levels of reservoir indicates that samples enriched in 18O. δD values of two reservoir unit (K1 and K2 + K3) are higher than the δD values of K4. The last highly D-depleted water sample could indicate that this formation water is affected by isotope exchange with clay minerals and/or by other fluids such as those rich in aqueous or gaseous hydrocarbons. Inferred compartmentalization from these geochemical methods is compared with independent evidences such as geochemical logs and horizontal permeability data which reconfirmed reservoir compartmentalization.