Laboratory and computational investigation of dynamics and permeability evolution in clay-smear type fault zones

Practical application of fault seal analysis for reducing risk in hydrocarbon exploration and CO2
storage, and for predicting the dynamics of reservoirs under stress, requires that both small and large
scale processes within and around fault zones are understood and that structural evolution is related
directly to changes in permeability through calibrations with available field and laboratory data.
In 2006 the research organizations CSIRO (Australia) and TNO (Netherlands) came together with
industry sponsors to form a research consortium to investigate the dynamics of permeability evolution
in clay-smear type fault zones in sandstone/mudrock sequences. The plan was rather ambitious,
requiring new developments in laboratory apparatus and in numerical modeling approaches to this
problem. The objectives were:
1. To create in the laboratory some of the largest scale shear zones attempted so far under
reservoir stress conditions, reaching 100 mm of displacement, and with sufficient freedom
of kinematics to allow 3-dimensional fault structures to develop.
2. To conduct the tests at a range of effective stresses reaching up to around 30 MPa faultnormal
stress, equivalent to several kilometers of burial.
3. To implement direct fluid flow and pressure monitoring during the dynamic shearing and
static loading of the model fault zone during its evolution; this required the development of
an entirely new self-sealing system for the fluid cell.
4. To dissect and image the fault zones produced in order to understand the structural
evolution on the fine scale in three dimensions.
5. To use a combination of finite element (FE) and discrete element modeling (DEM) to
recreate the experimental conditions of the laboratory experiments’ kinematics and
geomechanical responses and to extrapolate from the measured parameter sets into wider
and more continuous variations in rock properties and stress conditions.