Quantitative Evaluation Model of Carbonate Reservoirs Based on Multi-Level Fuzzy Theory

Abstract

The quantitative evaluation of carbonate reservoir is one of the key issues of oil and gas exploitation. However, due to the characteristics of carbonate reservoir, such as diverse physical distribution, complex pore-throat structure and strong heterogeneity, its quantitative evaluation is relatively difficult. Take the Lei 1 Member carbonate reservoir of Middle Triassic Leikoupo Formation in the Moxi gas field of Sichuan Basin as the example. The improved analytic hierarchy process is adopted based on 9 prioritized parameters which have direct influence on the quality of carbonate reservoir, namely porosity, permeability, water saturation, displacement pressure, average pore-throat radius, effective reservoir thickness, permeability variation coefficient, permeability rush coefficient and permeability range, to build a multi-level hierarchical structure model and quantitatively determine the relative importance quantitative indicators of all the parameters for reservoir quality. And fuzzy comprehensive evaluation method is used to build a quantitative evaluation model of carbonate reservoir. The evaluation results are well consistent with the actual gas capacity, which indicates that the mathematical model is available for quantitatively evaluating the carbonate reservoir and has relatively good feasibility.