Laboratory Drilling Test of Core Discing Phenomenon under Low Stress

The phenomenon of core discing has always been considered as a unique sign of high geostress area. With the in-depth study of the discing mechanism, there are various indications that the high geostress is not the main controlling factor of the core discing. Based on the geostress classification standard and engineering cases data, the stress level of complete granite prone to discing is determined in this paper. On this basis, laboratory drilling tests with different drilling speeds under high and low stress conditions are designed. The results show that high stress is not the key factor for core discing. When the drilling speed is fast, even if the confining stress is 0, core discing will occur. When the drilling speed is slow, the core can be taken completely even at high stress levels. Drilling parameters fluctuate with discing, and its peaks correspond to the core fracture location.