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<p>The study focuses on the Mishrif carbonate reservoir in the X oilfield, southern Iraq, which presents characterization complexities of a difficult nature due to its complex geology. The field, sited in the Zubair subzone, the most prolific and the southernmost of the Mesopotamian Plain hydrocarbon production units, is a good example of the structural complexity of the unstable shelf of the region of southern Iraq, where salt tectonics, basement faulting, and deformation of the region together produce characteristic anticline structures. This study uses an integrated petrophysical method combining core analysis from Wells 1 and 5, nuclear magnetic resonance (NMR) T2 distribution measurements, and conventional well log data to characterize the heterogeneous Mishrif carbonate reservoir comprehensively. A hierarchical pore classification system was developed based on mercury injection capillary pressure (MICP) analysis and geological observations, classifying the pore network into three different types: micropores, mesopores, and macropores. Through systematic calibration with MICP data, specific T2 relaxation time cutoffs were established to partition total porosity into these pore-size classes. The analysis shows that micropores mainly contain bound fluids, with a T2 cutoff value of 50 ms effectively describing irreducible water saturation. Strong relationships between NMR-derived porosity division and MICP-based pore size distributions confirm the integrated methodology. The method successfully quantifies critical reservoir parameters, including porosity, permeability, and pore size distribution. The results demonstrate that integrating core-calibrated NMR analysis with conventional petrophysical evaluation significantly enhances characterization accuracy in complex carbonate systems. This methodology provides essential parameters for reservoir engineering applications and establishes a robust framework applicable to similar heterogeneous carbonate reservoirs. The successful application of this integrated approach in the structurally complex Mishrif Formation emphasizes its potential for improving reservoir characterization in challenging geological settings. </p>

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Integrating NMR T2 distributions, CPI interpretations, and core data to evaluate the Mishrif reservoir in the X oilfield: a case study from Southern Iraq

  • 期刊论文

  • 发表日期：

    2025年12月2日

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  • H. A. Chafeet,
  • M. J. Ismail,
  • A. A. Lazim

摘要

The study focuses on the Mishrif carbonate reservoir in the X oilfield, southern Iraq, which presents characterization complexities of a difficult nature due to its complex geology. The field, sited in the Zubair subzone, the most prolific and the southernmost of the Mesopotamian Plain hydrocarbon production units, is a good example of the structural complexity of the unstable shelf of the region of southern Iraq, where salt tectonics, basement faulting, and deformation of the region together produce characteristic anticline structures. This study uses an integrated petrophysical method combining core analysis from Wells 1 and 5, nuclear magnetic resonance (NMR) T2 distribution measurements, and conventional well log data to characterize the heterogeneous Mishrif carbonate reservoir comprehensively. A hierarchical pore classification system was developed based on mercury injection capillary pressure (MICP) analysis and geological observations, classifying the pore network into three different types: micropores, mesopores, and macropores. Through systematic calibration with MICP data, specific T2 relaxation time cutoffs were established to partition total porosity into these pore-size classes. The analysis shows that micropores mainly contain bound fluids, with a T2 cutoff value of 50 ms effectively describing irreducible water saturation. Strong relationships between NMR-derived porosity division and MICP-based pore size distributions confirm the integrated methodology. The method successfully quantifies critical reservoir parameters, including porosity, permeability, and pore size distribution. The results demonstrate that integrating core-calibrated NMR analysis with conventional petrophysical evaluation significantly enhances characterization accuracy in complex carbonate systems. This methodology provides essential parameters for reservoir engineering applications and establishes a robust framework applicable to similar heterogeneous carbonate reservoirs. The successful application of this integrated approach in the structurally complex Mishrif Formation emphasizes its potential for improving reservoir characterization in challenging geological settings.