ABSTRACT
Recent tests have shown that the conductivity of a 20-40 sand pack is increased by blending angular sand with the very round product currently used in hydraulic fracturing. The oil and gas industry requires fracturing sand to meet high roundness specifications, according to the Krumbein and Sloss chart, for the purpose of providing the optimum geometric pack in the fracture. Indeed this will decrease point pressure on the sand grains and reduce crushing and fines generation in the sand pack, but tests indicate that the optimum geometric pack for crush resistance does not always offer the maximum conductivity through a sand pack.
Sand grains with a roundness factor of .5 (the minimum API standard for frac sand is .6) were mixed in 50/50, 62.5/37.5, 75/25, 87.5/12.5 and 100/0 blends with sand grains having a roundness factor of .8. These combinations were placed in a conductivity cell and tested at closure stresses as high as 10,000 psi. Several blends proved more conductive than the 100% highly rounded grains used as a control sample. This paper will show how the increased void space of a round-angular sand combination overcomes its susceptibility to crushing and provides increased conductivity, the most reliable measurement of a sand's overall performance.
