Case study · Geoscience & subsurface studies

Measuring permeability across 9 orders of magnitude: A custom high-pressure gas permeameter

For a civil engineering research laboratory, IRIAN Mecatronics designed and built a custom gas permeameter. The equipment measures the permeability of rock samples over a 9-decade range, under a confining pressure of 600 bar.

Client: University civil engineering research laboratory
Field: Geoscience
Technique: Intrinsic gas permeability measurement

01 — The research question

How can you measure a physical property over a very wide dynamic range with a single instrument?

Some physical properties, like the permeability of a material, can vary by several orders of magnitude from one sample to another. Standard sensors have a limited measurement range, forcing labs to use multiple instruments or switch sensors mid-test. This makes measurements discontinuous, complex, and expensive.

In this project, a research lab needed to characterize the gas permeability of rock samples ranging from highly porous to nearly impermeable, while simulating deep geological conditions (confining pressure up to 600 bar). Off-the-shelf flow meters, which cannot cover such a broad range, would have made the tests tedious and the results inconsistent.

The challenge: To measure both very high gas flow rates (permeable rocks) and near-zero flow rates (tight rocks) with a single device, without compromising accuracy at either end of the scale.

02 — Our approach

Our approach: From measurement principle to test cell

To solve this challenge, our engineering team made three key design choices that ensure performance across the entire range, fast measurements, and sample integrity.

Using an indirect measurement principle to cover the full range

Since no direct-reading flow meter can span 9 orders of magnitude, we based the measurement on the rate of pressure change in two calibrated volumes. This principle (the transient method), directly related to Darcy's law, is valid across the entire range. The user gets a single, continuous measurement without having to switch sensors.
Designing a specialized circuit to optimize speed and sensitivity

A single circuit would have been too slow for high permeabilities or not sensitive enough for low ones. We therefore designed two switchable circuits: an upstream 'high-pressure' circuit for high flow rates and a downstream 'low-pressure' circuit for minute flows. This optimizes the measurement time for each type of sample.
Securing the sample under high triaxial stress

To apply 600 bar of confining pressure without damaging the rock, we developed a self-compensating mechanical cell. It maintains isostatic pressure and protects the sample's integrity during pressurization cycles. This approach is central to our work in custom HPHT test benches for geoscience and subsurface studies.

03 — Beyond this project

Could this approach apply to your project?

Construction materials

To characterize the air or water permeability of high-performance concrete or geomembranes. The pressure decay measurement principle and dual-circuit architecture would still apply; the cell and test fluids would be adapted.

Food or pharmaceutical packaging

To measure the very low oxygen or water vapor permeability of barrier films. The downstream circuit of our test rig, optimized for infinitesimal flows, could be directly transferred. The cell would be designed for flat films under low differential pressure.

Technical textiles and membranes

To assess the 'breathability' of fabrics from waterproof to highly breathable. The pressure decay method with specialized circuits remains the most suitable approach, but the cell would be designed for flexible samples and low pressures.

04 — Specifications

The values for this project. Every system is custom-built, so they adapt to your requirements.

Show specifications · 10⁻¹² to 10⁻²¹ m² · 60 MPa (600 bar / 8,700 psi) · 50 mm

Technical specifications — Measuring permeability across 9 orders of magnitude: A custom high-pressure gas permeameter
Permeability measurement range	10⁻¹² to 10⁻²¹ m²
Maximum confining pressure	60 MPa (600 bar / 8,700 psi)
Sample diameter	50 mm
Sample height	30 to 100 mm
Test gases	Argon, Nitrogen, Helium compatible

IRIAN Mecatronics designs and builds custom high-pressure, high-temperature equipment for research laboratories, technical centres and industry.

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05 — FAQ

Frequently asked questions

Can this type of permeameter be used to measure permeability to a liquid like water?

No, this measurement principle is specific to compressible fluids (gases). For an incompressible liquid like water, a different method is required, typically based on measuring an injected volume at a constant flow rate. We design such systems using high-precision syringe pumps to set the flow rate and differential pressure sensors to measure the pressure drop.

Can this test rig be adapted for even higher confining pressures, such as 150 MPa?

Yes, absolutely. Designing equipment for extreme environment simulation is our core business. A pressure of 150 MPa (1,500 bar) or higher would require resizing the confining cell and circuits and selecting appropriate materials. The pressure decay measurement principle, however, would remain valid.

How can you measure permeability on non-cylindrical or very fragile samples?

The confining cell is always custom-designed to match the sample's geometry. For cubic shapes, films, or very fragile materials, we adapt the sample holder design and the way stress is applied. For detailed analysis of mechanical behavior, a custom HPHT triaxial cell may be a more suitable solution.

Are circuit switching and data acquisition automated?

Yes, full automation of the measurement cycle is standard practice for our custom test rigs. The control software manages switching between circuits based on the expected permeability range, pressurization cycles, acquisition of pressure vs. time data, and the final permeability calculation. This ensures repeatability and simplifies the operator's work.

Is your permeability, porosity, or diffusion measurement limited by your sensors' dynamic range?

Describe your challenge, no matter how specific. Our engineering team will analyze your project's feasibility and get back to you with a proposed approach.

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