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<p>Understanding the distribution of mechanical rock properties and in situ stresses within hydrocarbon reservoirs is essential for several reservoir geomechanics applications. This encompasses the analysis of wellbore instability, the assessment of reservoir compaction, and the planning of water or gas injection during the field’s lifecycle. In this research, a one-dimensional geomechanical model (1D-GMM) was developed based on a data from Mishrif oil reservoir in the Nasiriya field to estimate the stress distribution, deformation, and possible failure regions across the entire reservoir thickness as the available core samples are restricted for only discrete data points at particular depths. This reservoir has been separated into five parts, ranging from CI to MB-2, from top to bottom. Recent findings demonstrate that the cap rock units (CI, CII) possess diminished mechanical characteristics. This1D-GMM is essential for CO2-EOR as it allows for the assessment of reservoir connection and the optimization of CO2 injection. By the developed this model, it was indicated that the faulting regime in the Mishrif formation varies among wells, with some exhibiting a reverse (thrust) fault in reservoir units and a normal fault in barrier units, while others display a strike-slip fault in reservoir units and a reverse/thrust fault in barrier units. Nevertheless, the in-situ stress has significantly diminished in barrier units. Considering the aforementioned findings, it was identified that the Mishrif formation in Nasiriya discloses high mechanical rock strength in MB units, making it less dependent to fracturing under increased pressures. However, caution is warranted during gas injection operations in the upper sections near the barriers, as these areas demonstrate lower mechanical strength and exhibit reverse thrust characteristics in their reservoir unit. It is essential to closely monitor pressure fluctuations during gas injection to avert excessive pressure accumulation, which could result in fault reactivation, thereby increasing the risk of leakage and strike-slip events. The findings may facilitate improved CO2 injection methodologies, optimized management strategies for carbonate reservoirs, and augmented oil recovery while minimizing risks to caprock integrity.</p>

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Constructing one-dimensional geomechanical model to estimate the pre-production stress state in carbonate reservoirs

  • 期刊论文

  • 发表日期：

    2026年4月7日

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  • Saif S. Al-Godi,
  • Watheq J. Al-Mudhafar,
  • Dahlia A. Al-Obaidi

摘要

Understanding the distribution of mechanical rock properties and in situ stresses within hydrocarbon reservoirs is essential for several reservoir geomechanics applications. This encompasses the analysis of wellbore instability, the assessment of reservoir compaction, and the planning of water or gas injection during the field’s lifecycle. In this research, a one-dimensional geomechanical model (1D-GMM) was developed based on a data from Mishrif oil reservoir in the Nasiriya field to estimate the stress distribution, deformation, and possible failure regions across the entire reservoir thickness as the available core samples are restricted for only discrete data points at particular depths. This reservoir has been separated into five parts, ranging from CI to MB-2, from top to bottom. Recent findings demonstrate that the cap rock units (CI, CII) possess diminished mechanical characteristics. This1D-GMM is essential for CO2-EOR as it allows for the assessment of reservoir connection and the optimization of CO2 injection. By the developed this model, it was indicated that the faulting regime in the Mishrif formation varies among wells, with some exhibiting a reverse (thrust) fault in reservoir units and a normal fault in barrier units, while others display a strike-slip fault in reservoir units and a reverse/thrust fault in barrier units. Nevertheless, the in-situ stress has significantly diminished in barrier units. Considering the aforementioned findings, it was identified that the Mishrif formation in Nasiriya discloses high mechanical rock strength in MB units, making it less dependent to fracturing under increased pressures. However, caution is warranted during gas injection operations in the upper sections near the barriers, as these areas demonstrate lower mechanical strength and exhibit reverse thrust characteristics in their reservoir unit. It is essential to closely monitor pressure fluctuations during gas injection to avert excessive pressure accumulation, which could result in fault reactivation, thereby increasing the risk of leakage and strike-slip events. The findings may facilitate improved CO2 injection methodologies, optimized management strategies for carbonate reservoirs, and augmented oil recovery while minimizing risks to caprock integrity.