Frack Sand

20/40 mesh is the most widely used frack sand grade globally because it provides the optimal balance between fracture conductivity (larger particles create wider pore channels) and crush resistance. It is suitable for a broad range of reservoir depths and closure stresses, making it the default choice for most unconventional oil and gas hydraulic fracturing programs.

Closure stress increases with reservoir depth — approximately 0.7–1.0 psi per foot of depth. Shallow wells (<6,000 ft) can use coarser, lower-strength proppants (12/20, 16/30 mesh). Deep wells (>10,000 ft) experiencing high closure stress require finer, higher-strength proppants (30/50, 40/70 mesh) or ceramic proppants.

API RP 19C specifies standardised test procedures for: crush resistance (percent fines generated at specified stress), sphericity and roundness (Krumbein visual comparison), turbidity (suspended fines content in water), acid solubility, sieve analysis (particle size distribution), and bulk density. Compliance ensures consistent, comparable proppant quality across suppliers.

Frack sand is suitable for most low-to-moderate closure stress applications (typically below 8,000–10,000 psi). For high-closure-stress deep reservoirs (>10,000 psi), ceramic proppants (manufactured alumina or bauxite) provide higher crush resistance. However, improved frack sand processing has expanded application ranges, reducing ceramic proppant use in moderate-stress wells for cost savings.

Sphericity (how closely the grain resembles a sphere) and roundness (absence of sharp edges and corners) together determine how efficiently proppant grains pack in the fracture. Higher sphericity and roundness (≥0.6 per API) create more uniform packing with higher porosity and permeability, allowing greater hydrocarbon flow conductivity.