Dispersion of flexural waves in a borehole with a tensile fracture in an anisotropic stress environment
Dispersion of flexural waves in a borehole with a tensile fracture in an anisotropic stress environment
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DOI：
10.1111/1365-2478.13071
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发表时间：
2021-01
影响因子：
2.6
通讯作者：
K. Kayama;H. Mikada;J. Takekawa
中科院分区：
文献类型：
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作者：
K. Kayama;H. Mikada;J. Takekawa
利用偶极声波测井中弯曲波的频散特性，数值研究了水平各向异性应力条件下垂直井眼中的张裂缝效应。我们的三维模型包括一个充满水的钻孔和一个沿钻孔轴向与钻孔相交的拉伸裂缝。两个剪切波被单独激发，以产生在两个正交的径向方向上极化的粒子位移，使用两个偶极子源在两个极化方向上对齐。沿井眼轴线沿着在井眼中心放置一个等间距偶极子传感器的垂直阵列。假设由于水平应力各向异性，周围地层具有横向各向同性各向异性，各向同性平面平行于井眼轴线。我们研究了在我们的数值模型中沿沿着传播的弯曲波的色散，该模型包括具有不同深度的拉伸裂缝的快速或慢速地层。我们的数值计算结果表明，更深的穿透深度的拉伸裂缝，更高的剪切波极化垂直于拉伸裂缝慢和快地层模型。我们的研究结果表明，弯曲分散行为可以用来调查的穿透深度的拉伸断裂，可以通过钻井或水力压裂。
The effect of tensile fracture in a vertical borehole under anisotropic horizontal stress conditions is numerically investigated in terms of the dispersion of flexural wave generated in dipole sonic logging. Our three‐dimensional model comprises a borehole filled with water and a tensile fracture intersecting the borehole in the borehole axial direction. Two shear waves are excited individually to produce particle displacements polarized in two orthogonal radial directions using two dipole sources aligned in the two polarized directions. A vertical array of equispaced dipole sensors is placed at the centre of the borehole along the borehole axis. We assumed that the surrounding formation possesses transversally isotropic anisotropy with the isotropy plane parallel to the borehole axis due to horizontal stress anisotropy. We examined the dispersion of flexural waves travelling along a borehole in our numerical models that include either fast or slow formation with various depths of tensile fractures. Our numerical results show that the deeper the penetration depth of a tensile fracture, the higher the slowness of shear waves polarized perpendicular to the tensile fracture for both slow and fast formation models. Our results indicate that the flexural dispersion behaviour could be used to investigate the depth of penetration of a tensile fracture that can be produced by either drilling or hydraulic fracturing.