Experimental and finite element analysis of the API RP60 test

The compaction and fracture of brittle spherical particles in a cylindrical vessel were experimentally and numerically studied in the context of the American Petroleum Institute Recommended Practice 60 for proppants used in the hydraulic fracturing of oil and gas wells. Because pressures within the cylindrical vessel could not be directly measured, strain was experimentally determined via gauges along the outside surface. In addition, an epoxy resin was also injected at various loading stages to "freeze" the damage states for analysis. In addition, acoustic emissions were monitored in situ to determine damage signatures that could be correlated with the frozen test and strain measurement data. Experimental results were then compared to finite element simulations by using an assumed double-exponential pressure distribution applied to the inner face of the vessel. The results indicated that the assumed pressure distribution adequately described the loading state within the cylinder and revealed apparent stratification of damaged proppants near the top and bottom of the container. In addition, the damaged proppants and acoustic emission signatures showed that the damage increases progressively with the loading in distinct stages characterized by fracture and subsequent stress redistribution.