Max Watson

PhD student - Geo

Biography

Max completed a BSc. in Geology at James Cook University, Queensland in 1998. He worked with BHP Minerals as a geologist at the Cannington Silver Lead Zinc Mine in West Queensland in 1999. He then completed a BSc. (Hons) in Petroleum Geology at the ASP in 2000. Max is currently studying towards an MSc at the ASP researching mineralogical and physical changes in reservoir systems due to carbon dioxide infiltration.

PhD Research Project:

Characterisation of naturally occurring carbon dioxide - siliciclastic geological systems in Australia: Implications for long term CO2 storage

Supervisors: Dr Peter Tingate, Dr Geoff O'Brien

Funding support: CO2CRC

Scholarship support: CO2CRC

Project Description

This project focuses on the diagenetic reactions of reservoir and seal rock in the presence of high concentrations of carbon dioxide (CO2). Petrological examination of reservoir rock from the Pretty Hill Formation and the Waarre Sandstone in the Otway Basin reveals major mineralogical alteration due to CO2. Petrological techniques including optical analyses of thin sections, fractionated XRD, XRF, microprobe analysis, isotopic analysis and SEM taken from the reservoir intervals reveal that dissolution of lithic and felsic phases within the rock are dependant on CO2 concentrations, reactive surface area and water-rock ratios. Precipitation of new minerals, stable in the presence of CO2, has also taken place, including carbonate mineralogy permeantly trapping this greenhouse gas. CO2 accumulations within fractures of the Belfast Mudstone in the western Otway Basin also enables a petrological examination of the effects of CO2 on seal rock. Techniques including mercury injection capillary pressure tests (MICP) reveal the change in sealing capacity of mudstone affected by CO2.

Synthetic reactions are currently being conducted to gauge the reaction rate of some CO2-water-rock interactions. Pressures and temperatures are artificially created in a small chamber, where core sample is placed in the presence of CO2, at levels similar to what is recorded in natural CO2 accumulations. Water samples, taken weekly, assess the degree of reaction and geochemical models predict the product from the reaction chamber. Pre and post reaction petrological analysis quantifies changes to mineralogy, chemistry, and physical characteristics of the sample. The result of this study will be used to understand the reactions that will occur near the point of injection of CO2 in future sequestration sites.

Leakage of CO2 from these natural accumulations via fault conduits and seepage is also currently being studied. Transects run over known natural CO2 accumulations display maximum CO2 levels in soil directly over the faults. A GIS project over the Penola Trough region of the Otway Basin shows the occurrence of sampled CO2 gases along side features including vegetation, soil type, water analyses, rock type and near surface faulting. Seismic gas-seepage attribute mapping will be used to track the movement of any gases leaking from reservoirs. Areas with abnormal levels of CO2, attributed of leakage from CO2 reservoirs, will be examined for leakage rates, migration pathways and environmental impact.

This study of long-term, sealed accumulations provides proof to the concept underground storage of CO2. Through the study of natural analogues, projections for long-term CO2 reactions with siliciclastic reservoirs, including mineralogical trapping, and short-term CO2 reactions near the point of injection can be made for future storage of CO2.