Characterization of tertiary carbonate reservoir in the ABG oilfield using advanced magnetic resonance imaging logging (MRIL-P): a case study from southeastern Iraq
摘要
This study presents a novel approach to evaluating the petrophysical properties of the tertiary carbonate reservoir in the ABG oilfield by integrating Magnetic Resonance Imaging Logging (MRIL-P) data with conventional logs. The primary objective is to characterize porosity, permeability, pore size distribution, and fluid saturation, enabling the classification of reservoir layers into oil, water, water-flooded, and dry layers. MRIL-P data from well A-1 and conventional logs (gamma-ray, SP, and caliper) were processed using Geolog 20.0 software. Main parameters, including total porosity, effective porosity, free fluid porosity, capillary-bound fluid porosity, and permeability, were calculated using standard MRIL procedures. At the same time, pore structure and fluid types were analyzed using T2 distribution spectra, improved by differential and shift spectrum methods for fluid identification. The analysis identified 19 oil layers (57.8 m), 4 water-flooded layers (16.8 m), 2 water layers (11.5 m), 10 poor oil layers (28.5 m), and 8 dry layers (18.5 m) within the Asmari Formation. Oil layers showed high porosity (4.7–11.6%) and permeability (0.1–79.7 mD), with T2 spectra indicating large pore sizes and movable fluids. Water-flooded layers showed good porosity (11.5–14.2%) and permeability (0.4–444.6 mD) but low resistivity (2.0–2.4 Ohm m) and high water saturation (56–63%). Poor oil layers had lower porosity (4.2–9.7%) and permeability (0.01–0.4 mD), while dry layers displayed dense petrophysical properties with minimal movable fluid. The study shows the efficiency of MRIL-P logging in characterizing complex carbonate reservoirs, especially in distinguishing water-flooded layers and evaluating fluid saturation. The Timur–Coates model (KTC) proved more sensitive to fluid-type pore differences than the SDR model (KSDR). Integrating MRIL-P with conventional logs provides a strong framework for reservoir evaluation, offering detailed insights into porosity, permeability, and fluid distribution. Applying differential and shift spectrum methods for fluid identification in carbonate reservoirs is a significant development that enhances the accuracy of reservoir productivity evaluation and water flooding dynamics. The D9TWE3 measurement mode with dual TE and TW activations further ensured high-resolution data acquisition, emphasizing novelty and practical efficiency in heterogeneous carbonate formations.