Frac sand specs

Only sand that meets the American Petroleum Institute (API) standard specifications is likely to be used for frac sand.

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Here is a quick definition of the frac sand specifications:

Sieve testing frac sand spec

Actually, if you are doing initial exploration to see if your sand can be used for hydraulic fracturing, there is no “hard and fast” specification.

Of course, you want a good percentage of your sand to fall out into the common frac sand sizes, but other than that, no hard and fast rule.

If you are already selling sand to be used for fracturing, at least 90% of the tested sample must fall out in your advertised size.

Sphericity and Roundness testing spec

Krumbein and Sloss chart

This is the Krumbein and Sloss chart that is used to determine the roundness and sphericity of frac sand.

The API recommends that all frac sand have sphericity of 0.6 or higher and a roundness of 0.6 or higher.

This sphericity and roundness test is performed by comparing the individual sand particles, viewed under a microscope, to a chart (Krumbein and Sloss).

Sphericity measures how close a particle is to a circle in its overall shape.

Roundness measures how smooth each particle’s corners are.

Acid solubility frac test spec

API recommends that for frac sand sized 6/12 through 30/50, that a maximum of 2.0% of the sand’s weight be soluble in acid.

API recommends that frac sand sized 40/70 through 70/140 have a maximum of 3.0% of the sand’s weight soluble in acid.

Turbidity test spec for frac sand

Turbidity results when clay or silt in the sand get suspended when mixed with water.

API recommends that turbidity of frac sand should be 250 FTU or less.  FTU stands for “Formazin Turbidity Unit.”

FTU is a measure of how much light can pass through a suspension of the sand in water, mixed vigorously together and then allowed to stand for 5 minutes.

Frac Sand Crush Resistance Test Specs

The crush resistance test is performed by crushing a sample of the sand under increasing pressure, and then holding at the target pressure.

After the sand is crushed, a sieve analysis is performed.

The crushed sand particles that make their way into the pan are called “fines.”  The API has a spec for the maximum percentage of fines for each frac sand size.

Mesh size of sand Stress on sand (in PSI) Suggested maximum fines (% by weight)
6/12 2,000 20
8/16 2,000 18
12/20 3,000 16
16/30 3,000 14
20/40 4,000 14
30/50 4,000 10
40/70 5,000 8
70/140 5,000 6