Recent advances in downhole measurements allow to accurately measure drilling forces at the drill bit, and estimate the evolution of the rock strength along the well profile. This paper presents an experimental methodology that allows to measure drilling forces, at the cutter scale, with a sensor embedded behind a polycrystalline diamond compact (PDC) cutter, and to infer the 3D spatial distribution of the rock strength. Two experimental campaigns have been performed on a laboratory-scaled drilling rig and complemented with standard mechanical tests to validate rock strength estimations. In the first campaign, homogeneous synthetic rock samples have been prepared. The average rock strength of each sample derived from cutter force measurements and a cutter–rock interaction model, compares well with the one derived from mechanical tests. In the second campaign, heterogeneous synthetic rock samples have been prepared. They are made of two layers of gypsum mixtures of different strengths, separated by a slanted bedding plane. Based on the instrumented cutter measurements, the 3D spatial distribution of the rock strength has been reconstructed along its path. Rock strength estimations are consistent with results obtained from mechanical tests, and the reconstructed geometry of the bedding plane matches well its actual geometry. The experimental methodology and technology presented in this paper lay the foundations for estimating rock properties in 3D, at the drilling stage. It has the potential to provide geoscientists information about complex lithological structures at an early stage, reducing the need for expensive and time-consuming coring and logging operations.

井下测量的最新进展允许精确测量钻头处的钻井力，并估计沿井剖面的岩石强度的演变。本文提出了一种实验方法，该方法允许使用嵌入多晶金刚石复合片 (PDC) 刀具后面的传感器来测量刀具尺寸的钻孔力，并推断岩石强度的 3D 空间分布。在实验室规模的钻机上进行了两项实验活动，并辅以标准机械测试来验证岩石强度估计。在第一个活动中，已制备出均质的合成岩石样品。每个样品的平均岩石强度均来自刀具力测量和刀具-岩石相互作用模型，与机械测试得出的结果非常吻合。在第二次活动中，制备了非均质合成岩石样品。它们由两层不同强度的石膏混合物制成，由倾斜的层理平面隔开。基于仪器化刀具测量，岩石强度的 3D 空间分布已沿其路径重建。岩石强度估计与力学测试结果一致，并且重建的层理面几何形状与其实际几何形状非常匹配。本文提出的实验方法和技术为在钻井阶段评估 3D 岩石特性奠定了基础。它有可能在早期阶段为地球科学家提供有关复杂岩性结构的信息，从而减少昂贵且耗时的取芯和测井操作的需要。