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在水压致裂应力测量压裂特征参数中,瞬时关闭压力ps是重要的研究内容,因为它不仅直接代表最小水平主应力,而且在计算最大水平主应力时,该值又是重要的参数。ps判读的准确性和可靠性直接关系到水压致裂应力测量结果的可靠性与精度。结合3个典型的水压致裂测试曲线,分析了单切线法、dp/dt方法、马斯卡特方法和dT/dP法4种常用判读关闭压力方法的取值特点和适用性。结果表明,该4种判读方法对于不同形态的水压致裂测试曲线不具有普遍适用性,因此,对不同形态的水压致裂测试曲线进行判读关闭压力时,所选取的判读方法也不同。对于岩石完整、原生裂隙及节理不发育、岩石结构致密的水压致裂压裂段,应选取以上4种方法中2种或2种以上方法进行判读瞬时关闭压力值;对于岩石完整性差、原生裂隙及节理较发育、岩石结构较破碎的水压致裂压裂段,为取得比较可靠有效的关闭压力值,建议用单切线法计算机自动取值和dp/dt方法所取的关闭压力值。
The instantaneous closure pressure ps is an important study in the hydraulic fracturing stress measurement of fracturing characteristic parameters because it not only directly represents the minimum horizontal principal stress but also is an important parameter in calculating the maximum horizontal principal stress. The accuracy and reliability of ps interpretation are directly related to the reliability and accuracy of hydraulic fracturing stress measurements. Combined with three typical hydraulic fracturing test curves, the value characteristics and applicability of four commonly used interpretation closing pressure methods of single tangent method, dp / dt method, Muscat method and dT / dP method were analyzed. The results show that the four interpretation methods are not universally applicable to different forms of hydraulic fracturing test curves. Therefore, the different interpretation methods of hydraulic fracturing test curves of different forms are different when they interpret the closing pressure. For the complete rock, the primary fracture and joint development is not well developed, the rock structure of dense hydraulic fracturing fractures, the above four methods should be selected two or more methods to interpret the instantaneous closing pressure value; for poor rock integrity, primary In order to obtain a more reliable and effective closing pressure value, it is suggested to use the single tangent method and the dp / dt method to calculate the closing pressure value for fractured fractures with more developed fractures and more fractured rock structures.