SPWLA Glossary

Sand arch. The arch of sand created outside of an orifice or perforation on the formation side of casing or liner. For example, in unconsolidated sandstone the rock must have the property of dilatancy, or the property to expand, before the arch will form. The resulting arch, caused by the interlocking and wedging together of sand grains, prevents the flow of sand through a perforation. Cohesion is imparted to the loose grains forming the arch when the wetting phase is at irreducible saturation.