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目前,水压致裂测量应力的方法是以纯张破裂理论为基础的,仅考虑了周向主应力的作用。实际上,破裂是在三维主应力作用下发生的,现行理论与实际应有所差别。本文以大量室内模拟实验为依据,认为,在较深的深度或较大的围压下,由纯张破裂理论得出的结果可信度并不很大,钻孔壁受二维主应力作用的理论假设更符合实际应力状态。如果破裂是在二维主应力作用下发生的,初始裂纹应是剪切性质的破坏。依此提出了深部应力测量的实际计算公式,并应用到野外实际应力测量中。
At present, the hydraulic fracturing method for measuring stress is based on the theory of pure tensile fracture, and only the effect of circumferential principal stress is considered. In fact, cracking occurs under the action of three-dimensional principal stress, and the current theory and practice should be different. In this paper, based on a large number of indoor simulation experiments, it is believed that the results obtained from the pure tensile fracture theory are not very reliable at deeper depths or larger confining pressures, and the borehole wall is subjected to two-dimensional principal stress. The theoretical hypothesis is more in line with the actual stress state. If the fracture occurs under the action of a two-dimensional principal stress, the initial crack should be the failure of the shear property. Based on this, the actual calculation formula for deep stress measurement is proposed and applied to field actual stress measurements.