Fracture mechanics--Environmental aspects

Two wells installed in an unconfined, sandy aquifer in southern Florida exhibited low specific capacities and well loss coefficients resulting from borehole damage from drilling. Hollow-stem augers used to install the wells smeared drill cuttings onto the borehole walls reducing the hydraulic connection between the wells and the aquifer. Pneumatic fracturing was used to improve the specific capacity of both wells by improving the hydraulic connection with the aquifer. The pneumatic fracturing involved injecting air under high pressure into the surrounding formation to create a network of fractures. The success of the pneumatic fracturing was evaluated by recalculating the specific capacity and well loss coefficient of each well after the event. The results showed that both wells operated at increased discharge rates with improved specific capacities and well loss coefficients. High head loss coefficients indicated that the borehole damage was not completely repaired.