The injection of fluids into a compartmentalized formation induces pore pressure buildup and may result in reactivation of sealing faults. Among other variables, the pore volume compressibility (PVC) can affect the amount of pore pressure change during injection. PVC has been traditionally measured with isotropic loading compressibility tests. However, long and thin reservoirs subjected to depletion or injection typically follow a uniaxial strain stress path, rather than an isotropic stress path. Furthermore, injection unloads the reservoir rock by reducing effective stress, whereas depletion causes loading. This paper reports experimental measurements of the uniaxial strain unloading compressibility of Frio sand, a member of Tertiary strata in the Gulf of Mexico Basin. The uniaxial strain unloading compressibility increases nonlinearly from 0.29 to 1.45 GPa⁻¹ (2 to 10 µsip) as the mean effective stress is reduced from 26 to 5 MPa. The uniaxial strain unloading compressibility of Frio sand is about one third of the uniaxial strain loading compressibility at comparable levels of effective stress. The uniaxial strain compressibility of Frio sand is roughly one half of the isotropic compressibility. Reservoir simulation highlights that using incorrect pore compressibility values considerably underestimates the expected increase of pore pressure in a compartmentalized formation during injection. Uniaxial strain unloading compressibility of target reservoir rocks should be accurately estimated or measured to prevent excessive pressure build up in target storage formations during injection of CO₂ or any other fluid.

将流体注入分隔地层会导致孔隙压力增加，并可能导致封闭断层的重新激活。在其他变量中，孔体积压缩率 (PVC) 会影响注射过程中的孔压变化量。PVC 的传统测量方法是各向同性加载压缩性测试。然而，经历枯竭或注入的长而薄的储层通常遵循单轴应变应力路径，而不是各向同性应力路径。此外，注入通过降低有效应力来卸载储层岩石，而消耗导致加载。本文报告了墨西哥湾盆地第三系地层成员 Frio 砂的单轴应变卸载压缩率的实验测量。单轴应变卸载压缩率从 0 非线性增加。^-1（2 到 10 µsip），因为平均有效应力从 26 MPa 减少到 5 MPa。Frio 砂的单轴应变卸载压缩率约为有效应力水平相当的单轴应变加载压缩率的三分之一。Frio 砂的单轴应变压缩率大约是各向同性压缩率的二分之一。储层模拟强调，使用不正确的孔隙压缩率值大大低估了注入期间分隔地层中孔隙压力的预期增加。应该准确地估计或测量目标储层岩石的单轴应变卸载压缩率，以防止在注入 CO ₂或任何其他流体期间在目标存储地层中建立过度的压力。