Integrated reservoir quality index (IRQI): a novel approach for reservoir quality assessment.

Accurate reservoir quality (RQ) assessment is a critical component of hydrocarbon exploration and production, particularly in heterogeneous reservoirs with complex geological characteristics. The current study proposes an integrated reservoir quality index (IRQI) that combines parameters from different disciplines, including petrophysical, geomechanical and elastic attributes derived from well-log data. To ensure consistency among inputs, all parameters were normalized to a common range between 0 and 1, and no predefined or arbitrary weighting factors were applied. This approach allows the relative influence of each parameter to be governed by reservoir-specific geological conditions rather than subjective weighting assumptions. The proposed IRQI is implemented within a well–seismic integrated workflow, enabling reservoir quality evaluation at both well locations and the whole reservoir. At the well domain, IRQI was calculated using log-derived parameters and independently validated using laboratory core data. At the reservoir domain, IRQI was propagated into inter-well spaces using acoustic impedance inversion and seismic attributes, allowing continuous spatial characterization of reservoir quality. The methodology was applied to the Asmari Formation in two oilfields with diverse geological complexities and reservoir heterogeneities. One field exhibits a moderate geological complexity and heterogeneity, while the other is characterized by a high geological complexity and a pronounced reservoir heterogeneity. Unlike most previous studies that primarily rely on petrophysical parameters alone, this research integrates petrophysical, elastic and geomechanical properties into a single quantitative index. The performance of IRQI was evaluated at well locations and across the seismic domain in both fields, allowing consistent identification of high-quality reservoir intervals. The novelty of this study relies on the multi-domain integration of well logs-derived parameters, validated using core data, and field-scale application through well–seismic integration across multiple oilfields. The results highlight the robustness and applicability of IRQI for reservoir characterization in geologically heterogeneous reservoirs.