Sigra has a triaxial test rig designed to work with HQ (63.5 mm diameter) or HQ-3 (60.9 mm diameter) core. The axial stress can be loaded independently of the radial stress on the core.
Single phase permeability measurements using gas or water may be made on the core by causing flow in three ways:
- Axially along a solid cylinder
- Transversely across the core
- Radially to or from a central hole in the core.
- This latter process is readily conducted on core from IST stress testing.
Core permeability testing is not recommended for coals as their permeability is dependent on the cleating which is usually at a spacing that is sufficiently large that a statistically representative number of cleats are not contained in the core size tested. The same applies to many shales.