Rock Fracturing Techniques For In Place Leaching

The two most stringent parameters for in place fracturing of rock are the lack of any initial void space in the rock which to expand into and the ability to gain access only through drill holes. These two restrictions have proven so severe that as of today the only proven techniques for efficient fracturing are the contained nuclear detonation and hydrofracing. Both of these methods have highly developed technologies for their application. Hydrofracing has been a standard oil field practice for two decades, and the experience gained from a couple hundred underground nuclear detonations has resulted in a thorough understanding of the phenomenology of cavity and chimney formation. What is still lacking is a practical method to create a suit- able degree of fracturing for those ore bodies which do not meet the application criteria for either the nuclear explosion or hydrofracing. Nuclear applications must be restricted to thick ore deposits so as to take advantage of chimney collapse height--preferable in excess of 200 feet thick. Other requirements such as ground shock, containment, and radioactive contamination further reduce the number of sites that prudently can be selected.