Publication Name: PESA's Eastern Australasian Basin Symposium II
Authors: D.M. Kirste, M.N. Watson and P.R. Tingate
Date Published: December 2004
Number of Pages: 26
Reference Type: Book Section
Abstract:
Petrological and geochemical studies of a natural analogue for geological storage of C02 have highlighted thepotential of the Pretty Hill Formation from the Katnook area in the Otway Basin for gas-water-rock interaction
experiments and geochemical modelling. In this study a P-T-X experimental procedure was applied to a sample
representative of the reservoir prior to recent natural C02 influx, in order to develop geochemical models and so better understand geological storage of C02.
During the P-T-X experiments a core plug from the CO,-poor Katnook Field was subjected to an elevated C02 partial pressure and temperature in the presence of artificial brine. The evolution of the water composition and the mineralogy of the reservoir facies were then used to constrain equilibrium thermodynamic and kinetic reaction path computer modelling. The results predicted by the geochemical models and the P-T-X experiments fit the petrological observations and interpreted diagenetic evolution in the COrrich Ladbroke Grove Field.
Kinetics-based, reaction path models provide insight into the amount of potential mineral storage and time frames of this storage system. The experiments and modelling demonstrate the sensitivity of the formation water composition to reactions of C02 and the mineral phases. The predicted changes in composition and storage potential are strongly dependent on the initial mineral phases present. Local equilibrium may significantly influence the development of minor phases and the pH buffering capacity of the minerals ultimately controls the form of C02 storage (solubility, ionic, mineral).
The kinetics-based modelling of the Katnook reservoir rock indicates that the relatively fast reacting chlorite, containing Fe and Mg provides a suitable mineral sink of C02, greatly enhancing the ability of the system to store carbon. Model predictions after 20 years give values for mineral storage of C02 of 12 kg per cubic metre and after 1,000 years, 100 kg C02 per cubic metre.