Advanced Technology for Variable Cementation Exponent Determination. A Case Study from Thamama Reservoirs

This study develops an innovative methodology to address the challenge of determining the cementation exponent m in heterogeneous Thamama Group carbonate reservoirs. By investigating the critical influence of pore geometry on electrical behavior, we have implemented a novel approach for continuous m value determination, validated through several case studies from UAE reservoirs. The results of the study provide a robust solution for improving petrophysical evaluations in complex carbonate formations. Accurate estimation of the cementation exponent m in heterogeneous carbonate reservoirs presents significant challenges, as demonstrated by multiple studies showing how conventional "fixed m" approaches fail to capture complex pore geometry effects. This study develops an innovative workflow that synthesizes machine learning techniques with multi-variable correlations to overcome these limitations. By applying artificial intelligence to expand the SCAL dataset from just 149 core measurements to over 2,200 predictive points, we establish robust relationships between m and key reservoir parameters. The methodology specifically highlights the critical impact of microporosity, which reduces m to ~1.7 through enhanced electrical connectivity, while vuggy intervals exhibit higher values (>2.2) due to increased tortuosity. The neural network model, trained on this expanded dataset, combines MICP-derived pore structure characteristics (including Sw at 150 psi as a proxy for irreducible water) with conventional log responses to generate continuous m profiles. Validation against dielectric measurements and Nuclear Magnetic Resonance (NMR) data confirms the model's accuracy, with field applications demonstrating >10% improvement in hydrocarbon saturation calculations compared to traditional methods. The workflow's ability to reliably predict m variations represents a significant advancement for petrophysical evaluation in complex carbonate reservoirs, particularly for the Thamama Group where microporosity dominates the pore system.