Particle-Scale Investigation on the Influence of Formation Heterogeneity on Rock-Breaking Characteristics

Summary With the oil and gas exploration extending into deep and ultradeep strata, the complexity of formation dramatically increases. In-situ rock formations always display heterogeneity, yet the impact of the heterogeneity on rock-breaking mechanism remains unclear. This paper investigates the influence of heterogeneous formation with interbedded and conglomerate features on rock-breaking characteristics using a calibrated discrete element method (DEM) and a parallel bond model. Numerical results indicate that the proposed model can effectively capture realistic rock behavior. When cutting interbedded rocks, the cutting force fluctuates remarkably, indicating that the cutting teeth are prone to fatigue damage. The fluctuation of the cutting force curve is more intense at the transition position, implying substantial vibration when traversing the interlayer. Furthermore, the torsional impact mode is more conducive to the fragmentation of interbedded rocks. During cutting conglomerate formation, the size of the gravel in the conglomerate has a significant impact on the rock-breaking performance. The dynamic behavior of gravel particles can be categorized into four distinct stages, with each marked by various cutting force patterns. Interestingly, coarse gravels in front of the cutter facilitate the development of transverse cracks, creating a larger damaged zone. These findings offer deeper insights into the rock-breaking mechanism of formation with interbedded and conglomerate features at the particle scale.