摘要：Hydraulic fracture apertures predominantly control fluidtransport in fractured rock masses. Hence, the objective of the currentstudy is to investigate and compare three different laboratory-scale methodsto determine hydraulic apertures in fractured (Fontainebleau andFlechtinger) sandstone samples with negligible matrix permeability. Directmeasurements were performed by using a flow-through apparatus and atransient-airflow permeameter. In addition, a microscope camera permitted measuring the mechanical fracture apertures from which the correspondinghydraulic apertures were indirectly derived by applying various empiricalcorrelations. Single fractures in the sample cores were generatedartificially either by axial splitting or by a saw cut resulting inhydraulic apertures that ranged between 8 and 66 µm.Hydraulic apertures, accurately determined by the flow-through apparatus,are used to compare results obtained by the other methods. Thetransient-airflow permeameter delivers accurate values, particularly whenrepeated measurements along the full fracture width are performed. In thiscase, the derived mean hydraulic fracture apertures are in excellentquantitative agreement. When hydraulic apertures are calculated indirectlyfrom optically determined mechanical apertures using empirical equations,they show larger variations that are difficult to compare with theflow-through-derived results. Variations in hydraulic apertures as observedbetween methods are almost certainly related to differences in sampledfracture volume. Overall, using direct flow-through measurements as areference, this study demonstrates the applicability of portable methods todetermine hydraulic fracture apertures at both the laboratory and outcropscales.
