A fracture mechanics approach to rock drilling

A method for predicting drilling performance and estimating rock mass fracture properties is proposed. Based on the theories of static penetration and indentation fracture mechanics, the drilling forces may be determined by the associated contact areas and the contact stress under the tooth of the bit. As depth increases, the contact stress increases with the confining pressure. The relationship between the contact stresses with and without confining pressure was found to have the same form as for fracture toughness. This model can be also used to interpret the field data. When measurements while drilling are conducted, in-situ rock mass strength can be calculated. These in-situ parameters may be used to analyze borehole stability problems during both exploration and production. Verification of the proposed model was performed by comparing the model with some experimental results collected from the literature.