Conversion between particulate sand actual volume, effective volume, and weight (in a dispersed slurry) requires both apparent density of the sand and the volume fraction solids. Also called packing density, the volume fraction is the portion of the total volume taken up by the solids.

Settled solids, in a tank, separator, or accumulator do not take up 100% of the contained volume. The pore space between the particles contains liquid or gas, so density conversions must consider this “other” volume. The reciprocal of volume fraction is void fraction or effective porosity.

Packing density can be reported as fractional value (0-1) or percent value (0-100). A value of 1, or 100, means there is no void space and all volume is filled by solids. Analysis of produced sand samples in our lab, received from oil and gas fields around the world, shows that this material has a volume fraction ranging from 0.52-0.67. The average value is 0.62, which is the default we use in our calculations when a sample is not present. This value is dependent on particle size distribution and particle shape.

Analysis for volume fraction can be completed in the field or in the lab with a simple measurement.

• Use a glass or plastic graduated cylinder (100 ml is good size).
• Add dry material to level volume. Can be 100 ml if the solids are inert or will shrink, or can be 75 ml if the solids will expand.
• Add/measure water until level with solids. Allow time for solids to react with water – either shrink or expand. Also ensure no air bubbles are trapped in void space.
• Capture final solids level.
• Volume of water added is direct amount of void fraction.
• The photo below shows this setup – using a plastic 100 ml graduated cylinder and a burette for water addition.