Mechanical rock properties are becoming increasingly more important in petroleum exploration and production world-wide. An understanding of the stress, strain, and failure mechanics of rocks and their response to earth stresses can lead to enormous economic benefits in all phases of petroleum reservoir development. Over the last ten years, rock mechanics has emerged as a critical technology capable of lowering financial risk in drilling and well completions, qualifying exploration and development opportunities, and improving hydrocarbon productivity. Rock Mechanics in engineering and geoscience applications is a vital decision-making tool for high-angle and horizontal drilling, deepwater drilling, hydraulic fracturing, and completion of poorly cemented formations. Borehole instability, casing shear, subsidence, stuck pipe, and sand control issues cost the petroleum industry many billions of dollars annually. New concepts and improved experimental methods as well as straightforward c