Absolute Permeability

Permeability is a measure of the ability of a rock to transmit a single fluid phase through its pore structure.

Unlike the bulk density and sonic travel time, it is difficult to measure permeability directly in a well. It is traditionally measured in the laboratory on regularly shaped rock samples by forcing a fluid through the rock and recording the resulting fluid flux and pressure drops.

Ingrain complements and vastly expands laboratory permeability data sets by numerically simulating fluid flow through a direct digital representation of a real pore space obtained by high-resolution 3D imaging. Such imaging and simulations can be rapidly and massively conducted on physical samples of irregular shapes and sizes that are impossible to handle in the physical laboratory.

 The slow viscous flow needed for such permeability estimates is simulated using the lattice Boltzmann method (LBM). LBM mathematically mimics the Navier-Stokes equations of viscous flow by treating the fluid as a set of particles with certain interaction rules. Its great advantage over directly solving the equations of flow is that it directly handles the boundary conditions on a complex realistic pore surface. The outcomes are consistent datasets of permeability versus porosity correlations and pore geometries for various rock types, including tight gas sandstone, carbonates, and friable tar sands.
Computational set-up for permeability determination
The absolute permeability is computed in a manner analogous to a laboratory measurement: a pressure head or body force is directly applied to a digital sample. The resulting fluid flux is then computed and permeability is calculated according to the Darcy's equation.