Diagnostic fracture injection tests (DFITs) have been performed extensively in unconventional reservoirs to derive reservoir properties such as pressure, permeability, and closure stress. Since most horizontal wells in unconventional reservoirs are drilled in the direction of the minimum horizontal stress, prevailing studies typically presume that hydraulic fractures are oriented transverse to the wellbore direction. However, the near-wellbore stress concentration and perforation frictions may favor the initiation of fractures along the wellbore, which is perpendicular to the maximum horizontal stress. The possibility for the initiation of an axial fracture increases, if the injection rate is high enough or having low differential stress. In this study, we investigate the effect of initiation of the axial fractures on a DFIT test and its interpretation, using a fully coupled geomechanics and fluid flow model. First, we provide a model for the initiation and closure of axial fractures and transverse fractures during DFITs by coupling geomechanics with fluid flow. Then, using numerical simulations, we demonstrate that estimated closure stress can be misleading in the presence of an axial fracture. Finally, we discuss a potential method to determine the maximum horizontal stress under such circumstances.

诊断性裂缝注入测试 (DFIT) 已在非常规储层中广泛进行，以推导出储层特性，例如压力、渗透率和闭合应力。由于非常规油藏中的大多数水平井都是在最小水平应力方向上钻探的，因此普遍的研究通常假设水力压裂的方向与井眼方向成横向。然而，近井筒应力集中和射孔摩擦可能有利于沿井筒产生裂缝，该裂缝垂直于最大水平应力。如果注入速率足够高或具有较低的微分应力，则引发轴向断裂的可能性会增加。在这项研究中，我们使用完全耦合的地质力学和流体流动模型研究轴向裂缝的启动对 DFIT 测试及其解释的影响。首先，我们通过将地质力学与流体流动相结合，为 DFIT 期间轴向裂缝和横向裂缝的起裂和闭合提供了一个模型。然后，使用数值模拟，我们证明在存在轴向裂缝的情况下，估计的闭合应力可能会产生误导。最后，我们讨论了在这种情况下确定最大水平应力的潜在方法。我们证明，在存在轴向断裂的情况下，估计的闭合应力可能会产生误导。最后，我们讨论了在这种情况下确定最大水平应力的潜在方法。我们证明，在存在轴向断裂的情况下，估计的闭合应力可能会产生误导。最后，我们讨论了在这种情况下确定最大水平应力的潜在方法。