Maximum
Sustainable Carbon Dioxide Injection Pressures in the Naylor Field, Otway Basin
Van Ruth, Peter John1, Josh
Qiang Xu2 (1) Adelaide Univerity, Adelaide, Australia (2) Curtin
University of Technology, Perth, Australia
The Naylor field in the onshore Otway Basin, Australia has been chosen by the
Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) for a
geosequestration research and demonstration project. Carbon dioxide (CO2) will
be produced from the Buttress well (drilled into a natural CO2 accumulation)
and injected into an adjacent depleted methane reservoir (the Naylor field) at
a depth of ~2000 m. Methane production from Naylor resulted in a reservoir
pressure reduction of 7 MPa. Pore pressure has since increased by 5.5 MPa and the
CO2 injection is expected to increase reservoir pressure by a further ~ 3 MPa.
The Naylor field is bounded by faults which are optimally oriented for
reactivation in the current stress regime. Maximum sustainable pressures have
been predicted for: • near-borehole failure during injection (i.e. fracture
gradient); • failure of reservoir or cap rock, and; • the reactivation of
faults due to pressure increase in the reservoir. However, such estimates are
typically subject to large errors due, in part, to uncertainties in the stress
response of the reservoir to pore pressure changes (i.e. the reservoir stress
path). Hence, further calibration is required. The nearby Iona natural gas underground
storage facility, initially a methane field, provides an analogy for carbon
dioxide injection and storage in the Naylor Field. The Iona field is bounded by
faults which are also optimally oriented to reactivate in the current stress
field. The Iona structure was initially
depleted and has since undergone multiple periods of gas injection and
production without observable fault reactivation or damage to the structure.
The Iona analogy provides
additional support for the planned activities at Naylor.