An integrated petrophysical–geological framework for reliable permeability prediction in carbonate reservoirs, bridging core and log scales
摘要
Heterogeneous carbonate reservoirs pose a significant challenge for accurate permeability prediction, crucial for reservoir characterization and production planning. This study addresses this challenge by presenting an integrated multi-method workflow that synergizes petrophysical rock typing with hydraulic flow unit (HFU) delineation. Applied to the post-salt Albian carbonate reservoir of the Linguado field in Brazil, the methodology transcends the limitations of standard empirical correlations. Porosity was initially assessed using wireline logs and then compared with laboratory sample data from boreholes LIN03 and LIN10. The acoustic, density, and neutron porosity values for LIN03 yielded Pearson correlation coefficients (R2) of 0.29, 0.21, and 0.14, respectively. In contrast, LIN10 exhibited slightly better results with R2 values of 0.51, 0.50, and 0.37. The consistency of the approach was confirmed across both wells, with the larger dataset from LIN10 yielding marginally stronger initial correlations, where the sonic porosity was selected for subsequent permeability estimates due to its relative superiority over other estimates. After addressing this initial challenge, a permeability estimate was calculated using Timur’s empirical equation, yielding an R2 of 0.12. This outcome underscores the need for more reliable models that can incorporate reservoir zoning based on lithofacies, flow zones, and hydrodynamic flow units. This categorized method led to the formulation of regression equations for each hydrodynamic flow unit. While refined analysis can achieve greater accuracy by integrating results from multiple assessment techniques, the hydrodynamic flow units proved critical for accurately evaluating permeability relative to laboratory results, demonstrating the effectiveness of this method. The permeability of LIN03 showed an R2 = 0.97, whereas LIN10 presented an R2 = 0.98. These values can be used to forecast possible flow zones in additional oilfield boreholes. An advanced step in estimation methodologies was reached when the provided methodology culminated in a linear regression analysis to estimate permeability inside each hydrodynamic flow unit of the post-salt reservoir in southeastern Brazil.