Introduction: This patent aims to establish a water seal material balance equation applicable to high-temperature and high-pressure water gas reservoirs, fully considering various complex phenomena, based on the principle of material balance. Corresponding calculation methods for dynamic reserves (G) and water invasion constants (B) are proposed to provide a reliable theoretical basis for gas reservoir development decisions and ultimately optimize the gas reservoir development system and development strategy. Methods: Based on the principle of material balance, this study systematically incorporates key factors such as rock expansion, bound water expansion, formation water expansion, dissolved gas, and water sealed gas, and derives and establishes the material balance equation for high-temperature and high-pressure water gas reservoirs. Verify the applicability of the model through practical calculations (such as fitting the φ - R curve using the weighted least squares method), and conduct in-depth analysis of the influence of factors such as rock compressibility coefficient, reservoir heterogeneity constant (A), and water invasion constant (B) on the development performance of gas reservoirs. Results: (1) The increase in rock compression coefficient significantly enhances the stress sensitivity of the reservoir, leading to an increase in the error of dynamic reserve evaluation based on early production data; (2) The increase of reservoir heterogeneity constant A exacerbates reservoir heterogeneity, causing the gas recovery curve to shift from an upward trend to a downward trend, and the gas reservoir recovery rate gradually decreases; (3) The increase of water invasion constant B weakens the influence of water seal gas and formation water supply on formation energy, which helps to improve the final recovery rate of the gas reservoir; (4) Application examples show that the proposed method can effectively calculate dynamic reserves (such as G=27.9×108 m3 for a certain well), water invasion constant (B=1.3), and recoverable reserves (12.28 × 10 8 m 3). Discussion: Accurate evaluation of dynamic reserves and water invasion parameters of high-temperature and high-pressure water gas reservoirs is crucial for their effective development. Traditional material balance methods often overlook the comprehensive effects of complex phenomena such as rock expansion, bound water expansion, formation water expansion, dissolved gas release, and water sealed gas during the development process. Corresponding calculation methods for dynamic reserves (G) and water invasion constants (B) are proposed to provide a reliable theoretical basis for gas reservoir development decisions and ultimately optimize the gas reservoir development system and development strategy. Conclusion: The water seal material balance equation proposed in this study can effectively evaluate the dynamic reserves and water invasion parameters of high-temperature and high-pressure water gas reservoirs. Sensitivity analysis reveals the key controlling effects of rock compressibility (stress sensitivity), reservoir heterogeneity (constant A), and water invasion intensity (constant B) on the development performance and recovery rate of gas reservoirs. This model provides a solid theoretical foundation and practical guidance for the efficient development of high-temperature and high-pressure water gas reservoirs.
Yuan et al. (Fri,) studied this question.
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