Predicting Hydraulically Conductive Fractures - A Comparison of Methods

Reliable estimation of fracture stability in the subsurface is crucial to the success of exploration and production in the petroleum industry, and wider applications in earthquake hazard, hydrogeology and waste disposal. Being able to predict the stability of fractures in a reservoir (or seal) can enhance recovery and returns. Previous work has suggested that fracture stability is related to fluid flow in rocks: specifically, that more highly stressed fractures tend to exhibit higher rates of fluid flow. Barton et al. (1995) and Ferrill et al. (1999) described positive correlations of fluid conductive properties and ‘active’ fractures in basement rock. This contribution tests the applicability and robustness of the published correlations of stressed fractures and elevated fluid flow by the methods of critically stressed fractures (CSF) and dilatation tendency (Td), by comparing observed intervals of elevated fluid flow to the predicted values of CSF and Td. In this preliminary scoping analysis, the fracture stability of 219 fractures are calculated from wellbore data. Results show that the relationship between active fractures and fluid flow is more complex than described by expressions such as CSF and Td.