Direct Micromechanical Simulations of Rock Fracture During Indentation

51028-98-I Direct Micromechanical Simulations of Rock Fracture During Indentation--Tempress Technologies, Inc., 19308 68th Avenue South, Kent, WA 98032-1192; (253) 872-1980 Dr. Alan C. Mueller, Principal Investigator Dr. Edward Bohn, Business Official DOE Grant No. DE-FG03-98ER82695 Amount: $74,961 The development of advanced drilling techniques will benefit from a better understanding of the effects of formation and drilling fluid pressure on the creation and coalescence of rock microfractures during indentation and shear by mechanical cutters. Confining pressures tend to suppress the relatively efficient process of chip formation reducing the effectiveness of the drill bit. This project will apply a direct micromechanical simulation technique using boundary elements to model the growth and interaction of multiple cracks in granular rock under indentation, hydraulic, and in-situ loads. The technique uses a unique strategy to efficiently compute grain-scale to cutter-scale mechanisms. In Phase I, both 2-D and 3-D models will be exercised under indentation loading conditions to demonstrate the model¿s ability to reflect the organized growth of microfractures into larger scale macrofractures. In addition, the 2-D model will be coupled with a discrete fluid transport model to evaluate the grain-scale effects of fluid pressure on brittle-ductile transition. The model will be compared to laboratory experiments that show hydraulic-induced strain rate strengthening effects. Commercial Applications and Other Benefits as described by the awardee: A new design tool for evaluating novel drilling techniques and cutters in deep wells where fluid pressure effects are important would result in lower hard rock drilling costs for geothermal and fossil fuel recovery._