Unconfined compressive strength (UCS) is one of the crucial parameters for geomechanical modelling of unconventional reservoirs useful for the design of hydraulic stimulation of hydrocarbon production. In spite of a large amount of UCS data collected from the Lower Silurian and Ordovician shale successions of the Baltic Basin (northern Poland), no comprehensive study on this subject has been published so far. Here, we compile the results of 247 single-stage confined compressive strength tests (CCST) provided by our industrial partner from four exploration boreholes. Based on the integration of these results with geophysical logging data, including dipole sonic logs, we derive empirical equations describing the relationship between UCS and Young’s modulus or sonic wave slowness. Considering the strong anisotropy of elastic properties in shales we have introduced different empirical equations for UCS_V (vertical) and UCSh (horizontal), respectively perpendicular and parallel to bedding. The formula for UCSh is determined with less accuracy than for UCS_V due to scarce laboratory tests with bed-parallel loading. Based on the empirical formula proposed, we have estimated the VTI-type of anisotropy to be in the range of 12–27%, depending on the lithostratigraphic formation. The results of our UCS estimations are compared with the results of multi-stage CCST from the adjacent borehole. Both confined tests yielded similar results for UCS_V, with slightly higher values obtained from the multi-stage tests. In turn, a comparison of our solution with the results of true uniaxial compressive strength tests (UCST) for vertical samples from one of the studied boreholes revealed a significant discrepancy. The mean UCS results for shale formations from UCST are several times lower than those evaluated from the single-stage CCST. The usefulness of the results obtained for borehole breakout analysis is discussed.

无侧限抗压强度 (UCS) 是非常规储层地质力学建模的关键参数之一，可用于设计油气生产的水力增产。尽管从波罗的海盆地（波兰北部）的下志留统和奥陶统页岩层序收集了大量 UCS 数据，但迄今为止还没有关于该主题的综合研究发表。在这里，我们汇编了我们的工业合作伙伴提供的来自四个勘探钻孔的 247 次单级受限抗压强度测试 (CCST) 的结果。基于这些结果与地球物理测井数据（包括偶极声波测井数据）的整合，我们推导出了描述 UCS 与杨氏模量或声波时差之间关系的经验方程。_V（垂直）和 UCSh（水平），分别垂直和平行于层理。由于缺乏平行床加载的实验室测试，UCSh 公式的确定精度低于 UCS _V。根据提出的经验公式，我们估计 VTI 型各向异性在 12-27% 的范围内，这取决于岩石地层的形成。我们的 UCS 估计结果与相邻钻孔的多级 CCST 的结果进行了比较。UCS _{V 的}两个受限测试都产生了相似的结果，从多阶段测试中获得的值略高。反过来，将我们的解决方案与来自一个研究钻孔的垂直样品的真实单轴抗压强度测试 (UCST) 的结果进行比较，发现存在显着差异。UCST 页岩地层的平均 UCS 结果比单级 CCST 评估的结果低几倍。讨论了获得的结果对井眼突破分析的有用性。