Carbon Dioxide and Carbonate Cements in the Otway Basin: Implications for Geological Storage of Carbon Dioxide

Abstract

Understanding CO2 source and carbonate cements in natural gas accumulations is important for predicting the behaviour of anthropogenic CO2 in a reservoir system. The Otway Basin offers an excellent opportunity to examine late CO2-derived cements as an analogue for mineralogical storage of CO2. Understanding Otway Basin diagenesis and carbonate cement distribution is also of great significance to petroleum production in the region.Elemental and textural examination of Otway Basin cements has identified five carbonates in reservoir rock from CO2-rich gas accumulations. These carbonates show an overall increase in Fe2+ and Mg2+ relative to the calcites in CO2-free reservoir rock, indicating cation derivation from CO2 interaction with labile minerals.δ13C isotopes of 2.18‰ to -6.7‰ PDB from late carbonate cements in reservoirs containing CO2, confirm an inorganic CO2 origin. 3He/4He gas isotopic ratios of R/Ra > 1 indicate a predominantly mantle input for the CO2-rich accumulations.Degassing of magma associated with Pleistocene to Recent volcanics is suggested as the dominant, CO2 source for the existing CO2 accumulations. CO2 influx from the magmatic source was rapid, and is the most analogous scenario to injection of anthropogenic CO2. Natural influx of CO2 and the opportunity for mineralisation of CO2 is variable, with CO2 dissolving some original carbonate and precipitation dependant on pH, ρCO2, and available cations. Positive mineralogical CO2 storage occurs in the Pretty Hill Formation, due to a higher content of labile lithic minerals, with ~36 kg/m3 of CO2 (~48 kg/m3 carbonate) stored in the Ladbroke Grove Field from the current CO2 phase. The Waarre Sandstone has negative mineralogical storage of CO2, with less carbonate than similar reservoir rock without CO2, and therefore more CO2 being released from dissolution of early carbonates.

The Pretty Hill Formation as a natural analogue for CO2 storage: An investigation of mineralogical and isotopic changes associated with sandstones exposed to low, intermediate and high CO2 concentrations over geological time

“…Gas accumulations within the Pretty Hill Formation have highly variable CO 2 contents from <1 mol% to >90 mol%, making it a very attractive and arguably unique natural analogue. In addition, the formation has been well characterised by numerous earlier petrographic studies (e.g., Alexander, 1992;Little and Phillips, 1995;Martin and Baker, 1993;Phillips, 1991;Watson et al, 2004aWatson et al, , 2004b, and several cores have been recently analysed using Hylogger TM by the Australian Government, thereby opening up a new data source.…”

“…The importance of natural analogues to CCS have been recognised for a long time and several studies have been undertaken (e.g., Baines and Worden, 2004;Golding et al, 2013;Haszeldine et al, 2005;Higgs, 2011;Higgs et al, 2012;Kampman et al, 2013;Moore et al, 2005;Pearce et al, 1996;Stevens et al, 2003;Uysal et al, 2011;Watson et al, 2004aWatson et al, , 2004bWilkinson et al, 2009). …”

Helium in the Australian liquefied natural gas economy

“…Integration of the carbon isotope of carbon dioxide with the 3 He/ CO 2 ratio (Fig. 10) further supports the loss of carbon dioxide through either dissolution within the formation waters or carbonate precipitation associated with fluid-rock interactions and accompanying 13 C depletion in the residual gaseous carbon dioxide (Snyder et al 2001;Watson et al 2004;Tenthorey et al 2011). Such depletions in d 13 C CO 2 (i.e.…”

“…Oceanic rifts tend to have fluids with rather constant, but elevated, R/Ra ratios (7À9 Ra) indicative of MORB-like dominant mantle inputs, while continental rifting zones show the widest range in R/Ra (2À30 Ra), with the highest R/Ra ratios being associated with either plume heads or the most recent volcanic activity (Poreda et al 1986(Poreda et al , 1992Darrah et al 2013). Such is the case in the Otway Basin, where CO 2 -rich natural gases have the highest mantle helium input (Watson et al 2004). Areas above mantle plumes (hot spots) have consistently high R/Ra ratios (up to~40 Ra), with values depending on whether the rising hot fluids tap into either the upper or lower mantle and/or mixes with recycled crustal components (Polyak and Tolstikhin 1985).…”

Basic Research Needs for Geosciences: Facilitating 21st Century Energy Systems

“…These including the CO 2 -bearing domes of the central Rocky Mountains, high CO 2 gas fields, and the carbo-gaseous provinces of Europe Benson and Cook (2005) and Australia (Allis et al 2001;Czernichowski-Lauriol et al 2002;Watson et al 2004). In these regions, accumulations have held large volumes of CO 2 for tens of millions of years.…”