Importance of Recovery Factor in Volumetric Evaluation of Fractured Carbonate Reservoirs from the Southern Gulf of Mexico

Hernandez, Javier¹, Eduardo Montano², Jose Exparza³ (1) PEMEX Exploration and Production, N/A, Colombia (2) Pemex Exploraiton and Production, N/A, Colombia (3) Pemex Exploration and Production, N/A, Colombia

PEMEX's Exploration Evaluation Process for potential reserves volumetric estimates is derived from lognormal distributions of reservoir parameters such as productive area, net thickness, porosity, hydrocarbon saturation, gas expansion or oil formation and recovery efficiency. For fractured carbonates evaluations additional petrophysical parameters are included such as matrix porosity. This approach results in inconsistencies with production data from known fields. The option is to evaluate those using Recovery Factor (RF) distributions, from analogue fields, in which fracture porosity is accounted for. RF ranges for Mesozoic Fields in Southern and Offshore Regions have been updated and documented in order to apply them in volumetric evaluation of naturally fractured carbonate exploration opportunities and hence increase confidence in the estimates. Based on available field information three regional RF Areas were initially identified. Lognormal distributions were derived for each Area including the P10 and P90 values. At a later stage geological criteria were also considered (age, sedimentary environment and hydrocarbon type) which allow subdividing the regional Areas into eight Sectors with RF distributions based on more detailed analysis. These distributions are expected to reduce uncertainty in well location and exploration opportunity potential reserves evaluation. The application of this methodology will help Management in the decision making process by considering better possible volume scenarios and maximizing investment value.