Abstract

In hydraulic fracturing of producing formations in oil and gas reservoir engineering, as well as in coal gas drainage, hydraulic fractures are propped by solid particles—proppant that prevents closure of fractures under the action of compressive stresses in rocks. It is shown that alongside with lateral earth pressure, the compressive stresses in fractures are governed by additional compression generated by fracturing and by compression of rock in depression zone formed in the reservoir fluid inflow to the fracture. The compressive effect in the depression zone can be adjusted by reducing the rate of depression growth in time. This method of compression decrease in fractures is the most efficient in reservoir engineering and in shallow coal seam gas drainage. The compressive stresses in the depression zone are comparable with the lateral earth pressure, thus, the differential pressure step-up can make it possible to keep the stress–strain behavior of rock in the neighborhood of a hydraulic fracture within the limits of elastic deformation and to prevent the fracture closure with irreversible pressing-in of proppant in rock.

中文翻译：

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液压断裂中的压应力

摘要

在油气藏工程中的生产地层的水力压裂以及在瓦斯抽放中，水力压裂由固体颗粒支撑，支撑剂可防止岩石在压缩应力作用下闭合裂缝。结果表明，除了侧向土压力外，裂缝中的压应力还受压裂产生的附加压力和储层流体流入裂缝的凹陷区中岩石的压缩所控制。可以通过降低凹陷的生长速度来调节凹陷区域的压缩效果。这种降低裂缝压缩的方法在油藏工程和浅层煤层瓦斯抽放中是最有效的。