STRESS-DEPENDENT PERMEABILITY

Tests can be performed in multiple orientations, usually parallel to bedding/foliation and normal to bedding/foliation.

The following permeability tests can be carried out at elevated confining pressure (up to 100 MPa effective) using each of the hydrostatic apparatus:

Pore pressure oscillating method – a low amplitude, sinusoidal pressure signal of fixed-frequency is applied via the upstream pore fluid reservoir. The attenuated and phase-shifted downstream pressure signal is recorded. From this the permeability and sample storativity can be derived.

Pulse transient method – the simplest implementation is to maintain upstream pressure constant and to record the downstream response to the application of a small pressure difference between the upstream and downstream reservoirs.

Use of a simple reservoir model to illustrate the effect of stress-dependence of permeability 

In addition to permeability data, we use a simple reservoir model of a single hydraulic fracture to illustrate the effect of taking into account stress-dependence of permeability for different shales. Whitby mudstone data has been used by way of example. Failure to take into account stress-dependent permeability at the well test stage will likely lead to an overestimation in expected yield over time.

 

Our focus at Reo Tight Rocks (RTR) is on stress-dependent permeability measurements on core plugs. We offer permeability measurements over a range of pressures that will provide the necessary basis for modelling behaviour using suitable software. Please contact us if there is something you require that is not listed, however.

▲ Up to the top