The key focus for this study was to examine uncertainties related to numerical simulations of the effect of CO2 injection on shallow groundwater resources and petroleum fields in the near-shore area of the Gippsland Basin.
The Latrobe Group forms a sloping aquifer containing freshwater in the onshore area and becoming increasingly saline towards the offshore where the majority of petroleum fields are located. Assessing how CO2 injection affects the flow of formation water in the transition zone from fresh to saline water is critical for the selection of an appropriate storage site and for determining safe injection rates.
This project aimed to investigate the potential impacts of CO2 geological storage in the near-shore area of the Gippsland Basin. In particular, the study focussed on: the displacement of formation water; any change in the pressure system; the possible effects on both offshore petroleum fields and onshore ground water levels, and the effects on the salinity in the Latrobe aquifer.
- Numerical simulations of storage scenarios based on the basin-scale hydrogeological model.
- Geochemistry of formation waters. A detailed analysis of the major and minor compositions, and their distribution and variation with salinity together with isotopic analyses, will help in understanding the evolution of formation water chemistry and underlying geochemical processes.
Following the simulation of injecting CO2 for 20 years at 1-5Mt/year, the key conclusion were:
- The fluid inclusion data demonstrate that paleo-salinities of formation water in the Latrobe aquifer were generally higher than present-day salinities, suggesting that the low-salinity wedge is younger than the formation of the fluid inclusions and must have formed sometimes during the last 5 million years.
- No potential was shown for significant salinity increase in the onshore parts of the aquifer.
- Changes in formation water salinity occur mainly along the transition between freshwater and higher salinity water.
- CO<sub>2</sub> injection could introduce minor improvements to the production environment by creating a slight pressure increase in the onshore area to counteract the recent trend of under-pressuring due to petroleum production.
- This could provide pressure support to petroleum industry and reduce water level decline rate to the onshore water users
To access the final report from this project, please make a request through the enquiry form.