Publication
This study investigates experimentally hydraulic fracture propagation, arrest and closure in permeable rocks.Through a controlled laboratory experiment on a Molasse sandstone block under a true triaxial state of stress, hydraulic fracture propagation and closure was monitored via the measurements of fluid pressure, fracture opening at the wellbore and continuous recording of passive acoustic at sixteen sensors.The combination of acoustic data, fluid pressure, and fracture opening measurements offer an interesting dataset to better understand fracture closure.Both the width and pressure behavior upon closure are consistent with recent theoretical estimate.This notably justify the use of pressure derivatives with respect to the square-root of shut-in time to pick fracture closure.The scaled opening versus reverse time and scaled pressure over the square root of reverse time exhibits a linear behavior, in line with the expected theoretical behavior.As a result, the width evolution near closure can be used to estimate the leakoff coefficient.Interestingly, our measurements also reveal the existence of a irreversible/residual opening at the wellbore even after complete fracture closure, whose value is of the order of the Molasse sandstone grain size.This may be attributed to a small amount of shear slip/fracture mixed modality, potentially causing non-alignement of asperities of the fracture surfaces at closure.