ASTM D4525
Full Name
ASTM D4525 – Standard Test Method for Permeability of Rocks by Flowing Air
Scope
ASTM D4525 is a test method that determines the permeability of rocks by measuring the flow of air through them. It’s designed for rocks or well-indurated soils and is suitable for permeability values greater than 9.869 × 10⁻¹⁸ m² (0.01 millidarcy). The method is limited to rocks that are free from oil or any greasy substances.
The process involves flowing dry air through a rock specimen while carefully measuring several parameters:
- Absolute pressure of the air: this refers to the total pressure exerted by the air, including atmospheric pressure.
- Flow rate of the air: this measures the volume of air passing through the specimen per unit of time.
- Pressure differential across the specimen: this is the difference in air pressure between the inlet and outlet faces of the specimen.
Multiple tests (at least three) are conducted on the same specimen at varying mean air pressure values. The resulting permeability values from each test are then plotted against the reciprocal of the mean absolute pressure If these plotted points form a straight line, they are extrapolated to a value corresponding to an infinite mean air pressure. This extrapolated value represents the equivalent permeability of the rock for liquids.
Key aspects of ASTM D4525:
- Scope: this method focuses on determining the coefficient of specific permeability, a crucial parameter for understanding fluid flow through rock formations. It provides representative permeability values for rocks and well-indurated soils.
- Apparatus and procedure: the apparatus typically includes a permeameter, pressure and flow regulators, pressure transducers, and a flow meter. The rock specimen is placed within the permeameter, and dry air is flowed through it at controlled pressures. Accurate measurements of the pressure differential and flow rate are essential for reliable results.
- Limitations: the method is not applicable to rocks with permeability values less than 0.01 millidarcy or those containing oil or greasy substances.
- Units: while SI units are considered standard, reporting results in other units doesn’t signify non-conformance.
- Significance and rounding: observed and calculated values should adhere to the guidelines outlined in ASTM D6026, which addresses significant digits and rounding procedures.
Permeability is a critical factor in various geotechnical and geological applications, including:
- Oil and gas exploration: understanding rock permeability is crucial for predicting reservoir performance and optimizing extraction strategies.
- Groundwater management: permeability influences groundwater flow patterns and contaminant transport.
- Geotechnical engineering: permeability affects the stability of slopes, foundations, and underground structures.
- Geological storage: permeability is a key consideration for the safe and effective storage of carbon dioxide or other fluids in underground formations.
ASTM D4525 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the ASTM D4525 standard.
Contact us today to discuss your testing needs and how we can help you with your project.
Resources
Keywords
permeability; rock; air flow; flow rate; coefficient of permeability; pressure differential; flow; specific permeability; well-indurated soils; air; test method; sample; fluid