Gauging geological characterisation for CO2 storage: the Australasian experience so far...

Abstract

The techno-economic resource–reserve pyramid for CO2 storage is a concept for expressing the reduction in uncertainty in predicting realisable geological capacity for storing CO2 with diminishing spatial and temporal scales of study. A similar concept is implied regarding reduction in certain storage capacity with increasing density and resolution of usable data. In general, these are determined by the collective scope of characterisation objectives, which dictate the characterisation/modelling tools employed. The relationship between the uncertainty scale (the height) of the techno-economic resource–reserve pyramid and the characterisation requirements for real CO2 storage systems is defined by an increasing number of modelling studies in Australasia and elsewhere. Together, these studies represent a range of both spatial and temporal scales, and resolutions of study, and a range of starting-points in terms of an initial information base. This paper summarises a number of these studies to provide examples that elaborate the nature of different levels of the pyramid and its suitability as a metaphor for scale of study and storage capacity estimation certainty. These examples conclude with the first Australian demonstration of geological storage of CO2, the Otway Project, which sits notionally at the top level of the pyramid despite the absence of full requisite economic conditions. A discussion of the merits and shortcomings to the pyramid analogy follows, revealing some important aspects of the characterisation and modelling process that are not represented properly or conveyed effectively. It is concluded that the traditional techno-economic resource–reserve pyramid should be thought of as an idealised first-order conceptual analogy that has inherent limitations.