Sequestration Down Under

Transcription

1 INTERNATIONAL PITTSBURGH COAL CONFERENCE Sequestration Down Under Richard Sakurovs CSIRO Energy Technology, Newcastle PO Box 330 Newcastle 2300, Australia

2 Outline Sequestration: basics Some Demonstration projects in Australia: status Recent findings

3 Scale of the problem The mass of CO 2 produced by human activities (~25Gt/y as CO 2 ; ~7Gt/y carbon) is about the same as the mass of everything else produced by humans (including waste) put together. Total mass of humans is about 0.4Gt. Metabolic activity of all humans generates heat at the rate of 700 GW (120W/person). World human brain activity is about 100GW (metabolic, not electrical). The efficiency of this power is left as an exercise for the reader. The electrical power generated by human brains is not enough to run a Matrix.

4

5 How to reduce CO 2 emissions to the atmosphere. Reduced demand Increased efficiency of power generation Increased use of renewable resources Sequestration of carbon dioxide: collecting it and burying it

6 Sequestration Reducing the amount of anthropogenic CO 2 emitted to the atmosphere is necessary to reduce the increase of atmospheric CO 2 levels. This will require capturing and storing CO 2 from coal- and gas-fired power stations.

7 Some sequestration options Small possibilities (i.e. ~0.1% of total emissions) Cleaned flue gas as carbonation agent (replacing food grade CO 2 which is largely produced from CO 2 wells); CO 2 fertilisation in greenhouses Industrial processes using CO 2 Urea synthesis Aspirin Polycarbonates? CO 2 as an industrial solvent: advertised as green CO 2

8 option Biomass Deep sea Some more sequestration options Technology established Useful products Relatively easy x <100 yr storage Leakage to atmosphere Effective monitoring difficult <1000 yr storage Effect on ocean unknown Mineral carbonation Saline aquifers/ abandoned oil wells Coal seams Long term storage Naturally occurring process Large capacity Potential long term storage Most advanced deep sequestration option Potential large capacity Potential long term storage Difficult to speed up cheaply Injection rates slow

9 Options not mutually exclusive

10 Australia depends on fossil fuels

11 Australian studies: A brief history Australian Petroleum Cooperative Research Centre Project GEODISC for identification of potential sequestration sites in Australia CO2 Cooperative Research Centre Otway basin demonstration project being set up.

12 CO2CRC GEODISC Outcomes

13 Coal fired power stations

14 Sequestration current and planned Table 1. Estimates of total amounts of geologically stored CO 2 in existing and advanced proposed projects to 2015 (Cook, 2006). PROJECT COMMENCED Anticipated amount injected by: Sleipner MT 11MT 13MT 18MT Weyburn MT 9MT 12MT 17MT In Salah MT 5MT 7MT 12MT Snohvit MT 2MT 5MT Gorgon MT Peterhead/Miller MT 8MT California MT FutureGen MT Nagaoka KT 10KT 10KT 10KT Frio KT 4KT 4KT 4KT Ketzin KT 50KT 50KT Otway KT 100KT 100KT TOTALS 17MT 26MT 37MT 96MT

15 Some planned and potential Australian activities Otway Basin (CO2CRC) depleted gas well Gorgon, Western Australia aquifer Latrobe Valley depleted oil wells; coal seams are present Hunter Valley & Queensland (coal seams)

16

17 CO2CRC Otway basin

18 Demonstration project Otway basin Anticipated injection rate: ~50kt/year, 2 years. Source gas: 90% CO2, 10% CH4 Injection starts: Injection depth: 2100m Aims include to develop expertise in the area; demonstrate the feasibility of the program, monitor gas release, get community involvement.

19 Gorgon, Western Australia Planned natural gas project (ChevronTexaco, Australia). Gas has 14 mole % carbon dioxide, which will be reburied nearby. Total amount of CO 2 in reserve ~75Mt Potential sequestration rate: 4Mt/a Sequestration depth: 2.3km Starting 2010, subject to environmental approval* APPEA J *DA currently rejected by WA EPA

20 Australian research areas Sequestration targets Saline aquifers and old oil wells: seen as effective targets because of large capacity and large potential injection rates Coal seams: this option is explored because many major power stations in Australia don t have ready access to suitable aquifers but are located close to unmineable* coal seams * unmineable : most restrictive definition is unsuitable even for underground gasification. These seams are thin, high-ash, deep. * Note that there is more dispersed carbon underground than oxygen available to combust it.

21 Storage in coal Australian context ~ Mt CO 2 storage capacity May be a conservative estimate Relies on estimates of the coal resource Other potential targets not well characterised high-ash coals or coaly sediments Carbonaceous shales Most storage in coal basins located in eastern states areas with large CO 2 sources other potential sequestration targets are not known to exist This is the motivation for considering coal

22 sequestration feasibility for coal Coal adsorption capacity Permeability, diffusibility swelling Adsorption rate onto coal Fractures, cleats In coal Nature of surrounding material Flow rate Into coal Technical feasibility of sequestration Well design

23 Feasibility? Economic feasibility determined by wide range of factors including geology, coal properties, reservoir capacity, gas price Reservoir characteristics determine the operational costs such as injection rates, well spacing. Feasibility will be highly site specific

24 Some research areas Natural Analogue studies Adsorption behaviour at high pressures associated with injection into deep coal seams Coal swelling Improved representation of adsorption in reservoir simulation

25 Long term stability: Natural Analogue Studies. Magmatic CO 2 release into coal seams in New South Wales ~35Ma; isotopically different to in situ generated CO 2. Has been held with little release since that time. Within seam variation shows CO 2 generally enriched towards the higher points of the seam, methane towards lower points. Some has migrated ~ km over that time. Conclusion: there are coal seams in which carbon dioxide can be stored for millions of years.

26 Where s the CO 2 in coal? In the large pores of coal as a gas Adsorbed on the coal surface Possibly dissolved in the coal itself, with or without concomitant swelling

27 Some problems measuring sorption

28 CO2 Sorption by Argonne Premium coals 80 Excess Adsorption (kg t -1 ) Beulah Zap Illinios Pocahontas Gas Density (kg m -3 )

29 Coal swelling Volume swelling of all Australian coals examined to date is about 1.5% and reaches a maximum at about 5 MPa. REPOCOL (Poland) samples swell to about 2.5%. swelling of three coals volume % change Aus 1 Aus 2 REPOCOL Pressure (MPa)

30 Sorption characteristics Some coals can adsorb up to 10% of their weight of CO 2 ; any porosity is an additional storage capacity. However most coals sorption capacity is about 6-8 wt% Different coals have different sorption capacity and the difference at high pressure (15MPa) is not predictable from low pressure (5 MPa) studies Supercritical CO 2 expected to strongly change the physical structure and behaviour of coal CO 2 swells coal (typically ~1-2% volumetric) and will therefore reduce its permeability

31 Enhanced coal bed methane CO 2 is supposed to readily displace methane on a ~2:1 molar ratio. Not supported by mixed gas studies, which appear to show similar affinities by both gases (though mixed gas studies are not straightforward to interpret). How the CO 2 is adsorbed by coal and why methane sorption capacity is apparently so different is not known.

32 Limitation to coal seam sequestration Major limitation is seen to be slow rate of injection: lots of wells would be required. Thus we need to find coal seams that are highly permeable (eg via cleats) or ones closely connected to permeable sandstones.

33 Some future directions Adsorption work CO2 injected into coal seams will probably not be pure. The impact of these other materials on coal needs to be examined. Water affects the sorption, swelling and diffusivity characteristics of coals. Methane/ carbon dioxide mixtures need to be examined as well. Mineral matter influences need to be identified. A good sorption model needs to be developed CO2 injectivity work Characterise the permeability with adsorption behaviour for coals of interest

34 Summary Australia contributes a high level of carbon dioxide on a per capita basis, due to most of its electricity being generated from coal. There are significant sequestration projects planned over the next few years. Research is active in the CO 2 sequestration areas, using saline aquifers and coal to sequester CO 2.