full announcement

IDEAL STRESS REGIME FOR OLYMPIC DAM GEOTHERMAL PROJECT
· CSIRO study supports view that geothermal licences are influenced by an ideal stress
regime
· “Ideal situation for generating an optimal heat exchange reservoir” - CSIRO
· Green Rock Energy to measure actual size and orientation of principal stress directions
with mini-hydro fracc in preparation for deep stimulation program
Green Rock Energy (ASX:GRK), a leading geothermal energy company, today announced that
studies by the CSIRO of data from the Company’s Blanche No. 1 well supports the Company’s
view that its geothermal leases at Olympic Dam are influenced by an ideal stress regime for a
geothermal heat exchange reservoir.
The study by the CSIRO of the in-situ stresses using drill core and drill log data from the hot
granites drilled in Blanche No. 1 (which was drilled to 1.93km depth, by the Company, alongside
the Olympic Dam mine) indicates that the two principal horizontal stress directions from the hot
granites are greater in magnitude than the principal vertical stress direction.
According to the CSIRO study : “the vertical stress being the minimum stress implies that
hydraulic fracture orientation and fluid flow in a stimulated zone are most likely to be in a subhorizontal
direction. This is an ideal situation for generating an optimal heat exchange reservoir
that would allow a maximum distance between injection and production wells.”
Water pumped through fractures that open in a sub-horizontal direction will optimise the recovery
of heat from the granites. Water circulated between injection and production wells essentially
would be travelling horizontally through the granites as it gathers the heat trapped in the granites.
A sub-horizontal pathway through the granites means that the heat exchange process would be
maximised. If the pathways had not been sub-horizontal, the water travelling through the
fractures connecting the wells would pass from hot rocks to cooler rocks at shallower depths,
reducing the effectiveness of the underground heat exchange process.
Green Rock Energy’s next step will be to measure the actual size and orientation of these
principal stress directions in its forthcoming mini-hydrofrac to be carried out this year in its
Blanche No. 1 well under contract with the CSIRO. This should substantially reduce both the
risks and costs of the deep fracture stimulation program by providing the Company with data to
engineer the drilling of the deep wells and to optimise the design of the fracture stimulation
program connecting those wells. The Company is in the process of securing a suitable drilling rig
for this purpose.
About Green Rock Energy
Green Rock Energy is undertaking the evaluation of an engineered geothermal system (EGS) at
its Olympic Dam Project, located within 10 kms of BHP Billiton’s Olympic Dam copper and
uranium mine, in preparation for the construction of a series of EGS reservoirs to provide the
heat energy to power a base load power plant in excess of 400MWe. In Hungary the Company
is working on developing geothermal power from hot geothermal water trapped in sedimentary
rocks.
Adrian Larking
Managing Director
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