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L’énergie dans le développement de la Nouvelle-Calédonie

 | 
Yves Le Bars
, 
Elsa Faugère
, 
Philippe Menanteau
, 
et al.

Emissions and the reduction of greenhouse gas emissions in New Caledonia

How could New Caledonia make the most of its geological position in terms of research and experimentation into CO2 storage technologies?

Full text

1There are three potential options for CO2 storage:

  • The immersion of CO2 (liquid) in the deep ocean: this removes difficulties in terms of efficiency, cost, environmental impact and the durability of storage. Such techniques are still at the research stage.
  • Storage by ex situ mineral sequestration (mineral carbonation using waste): this process, which consists of industrially attaching the CO2 to inorganic carbonates, is currently at the demonstration stage (pilot site) and requires energy for carbonation as well as plants to be constructed where this operation can take place.
  • Storage in geological formations: this option is currently more on track for possible implementation. At a global level, several projects have achieved technical maturity but have not yet – because the cost per tonne of CO2 emitted is not sufficiently high – become economically viable other than to achieve, for example, fuller use of petroleum reserves. Australia is one of the five major global centres conducting research into geological storage.

BRIEF SURVEY OF NEW CALEDONIA’S GEOLOGICAL SITUATION

2The archipelago of New Caledonia is located in the transition zone between the Australian continent and the Pacific ocean plate. The island of New Caledonia (Grande Terre) corresponds pro parte to the revealed northern part of the Norfolk Ridge (figure 10) which is nothing more than a remnant of the eastern margin of the super-continent Gondwana which became separated from Australia around one hundred million years ago. Further to the north, the Loyalty Ridge is made up of submerged ancient volcanic edifices which were then covered with major carbonate reef deposits. Sedimentary basins, whose economic potential is currently being evaluated, run along these two islands.

The presence of peridotite and basalt massifs

3The geological history of New Caledonia, while complex, is relatively well known. Grande Terre resulted from the emergence of an orogenic prism (mountain chain) formed over between 36 and probably 28 millions years and which spread to the west in a geodynamic context of subductionobduction. This obduction manifested itself in a spectacular way with the development of a thrust fault towards the south-west of the oceanic lithosphere in the Loyalty Basin on Grande Terre. The remains of a layer of peridotite settled below the basin of the Loyalty Islands and found in shallow sediments along the eastern coast still bear witness to this thrust fault. This layer of peridotite still covers part of the island of New Caledonia today, forming part of its richness and originality. Peridotite today forms a major mass which makes up one third of Grande Terre (5 500 km2) across the south and along the western coast. The southern mass is the largest in world after that in Oman; it could be 3 000 m thick in parts.

4This exceptional abundance of ultrabasic rock is not only a source of considerable reserves of nickel and cobalt, it may also contribute to the geological storage of CO2 via carbonation.

5On the western coast, the layer of peridotite overlaps with the geological unit of Poya which is a pile of overlapping scales of oceanic crust which is made up of 95 % basalt (the unit is also known as the basalt layer). This basalt extends over a large area, showing on the surface of the northern half of the western coast.

Major but little known sedimentary basins

6The sedimentary basins associated with neo-Caledonian orogenesis along the western edges and to the west of New Caledonia, although well known for their oil potential, remain under-explored. These sedimentary basins represent important potential in terms of CO2 capture since they may contain future oil reserves and saline aquifers.

Figure 10 Geological map of New Caledonia by Pierre Maurizot, BRGM-Dimenc, 2001
The belt of peridotite forms a third of the surface area of Grande Terre which is located close the centre of CO2 emissions. The unit of Poya, which stretches along a large section of the western coast, is made up primarily of basalt (95 %) which also supports CO2 storage.

CO2 STORAGE IN GEOLOGICAL FORMATIONS: BEST PRACTICE

7The most conventional CO2 geological storage solutions found in the sedimentary basins are already commercially developed where they deliver benefits other than CO2 storage. Of these solutions, New Caledonia can immediately eliminate enhanced methane recovery in a bed of coal; indeed, coal reserves her are not large enough to deploy this process.

8On the other hand, we should include in situ mineral sequestration in the basic rocks (basalt) or ultra-basic rocks (peridotite) among the geological storage options which can be envisaged in the Territory. This less conventional option is at the research and demonstration stage (two pilot sites globally) and could prove an excellent area for experimentation in New Caledonia with results which could feed into international research networks.

Geological sequestration in sedimentary basins

9Sedimentary basins currently provide the largest storage potential on a planetary scale. The oil industry has kicked off with some commercial and demonstration projects in recent years in partnership with national and international research networks. These projects have been shared throughout the world to varying degrees.

Hydrocarbon deposits

10Rocks holding oil and gas (porous rocks) have proven that they are impermeable over millions of years; they could therefore be used to store CO2. Natural deposits have also been found during exploratory searches for oil and these have then been used industrially (the Montmirail reserve in Drôme for example). Hydrocarbon deposits currently constitute the simplest method of geological storage to implement, and the most economic.

CO2 storage in an oil field using enhanced recovery

11CO2 injection technology is already familiar to the oil industry which has been practising enhanced oil recovery since the 1970s. CO2 is injected into the deposits during extraction in order to reduce the viscosity of the oil. At the end of the energy recovery cycle, the CO2 can be captured rather than released into the atmosphere. Of the currently operational storage sites, one of the largest is the commercial project at Weyburn in Canada – an international project which commenced in 2000 under the aegis of the IEA – where 3 000 to 5 000 tonnes of CO2 are injected each day. This project, in which the European Union and Total are also participants, is set to last 15 years and will enable 20 million tonnes of CO2 to be stored permanently at the same time as 130 million barrels of oil are recovered.

CO2 storage in old exhausted or depleted gas fields

12Old exhausted or declining (depleted) oil and gas reserves also provide highly economically interesting storage sites. Several experimental pilot projects are underway at a global level with a view to testing and demonstrating the reliability and durability of this form of geological storage over the long-term. In France, the first plot project has just commenced at the former gas reserves in Lacq (Pyrenees) where 15 000 t of CO2 are to be injected into a depleted reserve over a two-year period. The project is being driven by Total which has the French scientific community around it (IFP, BRGM, Cregu, CNRS, universities). On the same scale of size, Australia in 2008 began its Otway pilot project (CO2CRC Otway Project) which the IEA considers to be one of the most illustrative in the world in terms of monitoring (100 000 t of CO2 will be injected there over a period of two years). Elsewhere, the IEA is evaluating the storage capacity of exhausted or depleted hydrocarbon reserves for up to 920 Gt of CO2.

13Ongoing research, funded by the oil companies and the public purse, focus on tools and techniques to monitor the impermeability of storage sites (leaks while drilling, cover seals). Currently, it is felt that leaks should not exceed 1 % of the total CO2 stored over 1 000 years.

Saline aquifers

14Like oil deposits, deep saline aquifers are found in sedimentary basins in the sea and on land, but they are far more common and not as deep down. The CO2 injected into the deposit remains sequestrated by means of hydrodynamic capture, solubility of the fluids on site and by mineralisation. Aquifers must be located at a depth of greater than 1 000 m to allow storage of CO2 in its supercritical state.

15Research programmes into aquifers are less advanced than those that relate to hydrocarbon deposits, although several demonstration projects are already underway. In 1996, the Norwegian oil company Statoil launched an initial commercial experiment (the Sleipner European project) to store1 million tonnes of CO2 per annum in the North Sea. The second, better known, commercial project is In-Salah in Algeria (BP, Sonatrach, Statoil) which began in 2004 and under which CO2 from the extraction of natural gas is reinjected (1.2 million t/annum) into the aquifer of the productive gas field making this project unique in the world. In France, the Paris sedimentary basin has been earmarked to carry out an initial evaluation of aquifer storage potential prior to commencing a demonstration project.

16In common with hydrocarbon deposits, research into saline aquifers will focus primarily on how stores behave over the long-term, although concerns regarding how well sealed they are is more important. According to the IEA, deep aquifers offer the largest CO2 storage capacity at a global level (400 and 10 000 Gt).

The sedimentary basins of New Caledonia present enormous potential

17The presence of sedimentary basins on the western cost of New Caledonia is undoubtedly an advantage. These basins are located relatively close to the CO2 emission centres; they inevitably contain saline aquifers but remain little explored. The geological context is relatively well known but we will have to await new oil exploration activities in order to properly evaluate the storage potential.

18If hydrocarbon deposits are discovered during planned short and medium-term exploration, lower cost geological stores of CO2 using enhanced oil recovery could be envisaged initially, followed by storage in depleted deposits. The discovery of hydrocarbon deposits on the western coast of New Caledonia, close to the CO2 emissions centres, is not ruled out. We are already familiar with the Gouaro anticline where a small accumulation of gas was detected in low quality reserves. Other comparable structures are sure to exist on the west coast as new exploration activities will demonstrate. If deposits are found further afield in sedimentary basins yet to be discovered off shore of the economic exclusive zone of New Caledonia, reasonable methods of transporting CO2 in liquid form by sea will need to be found (according to the IPCC, a distance of 300 km between the emissions site and the storage site is reasonable), although costs will increase.

In situ mineral sequestration in basic and ultra-basic rocks

19The idea of converting CO2 by mineralisation is based on observation of how carbonated rocks form in nature over geological timescales. Following interaction between aqueous fluids and fragments of silicate rock, calcium and magnesium first dissolve and then precipitate in the presence of carbon dioxide in the form of carbonates and magnesite. We know how to artificially reproduce these natural reactions which has led to different avenues of research into the mineral sequestration of CO2.

20In situ mineral sequestration thus involves injecting CO2 into basic (basalt) or ultra-basic (peridotite) rocks such that it is captured naturally in a mineral form through carbonation (transformation of the rocks into carbonates). Major experimental studies are underway to quantify the speed of mineralisation and the effectiveness of this process. Research is also being carried out into the potential of micro-organisms living at great depths to improve mineralisation. If it works, this process will have the advantage of being one of the most cost-effective, and will stabilise the sequestration of CO2 over millions of years. In addition, this storage option overcomes the risk of leaks which is the major problem with gas sequestration in oil reserves or saline aquifers.

Sequestration in basalt

21Initial studies into in situ mineral sequestration have focused on basic rocks, and basalt in particular which is the most reactive rock for mineral sequestration of CO2. We know that basalt found on the surface of the planet consumes atmospheric CO2 through a process of alteration. Basalt represents only 5 % of the continental surface. There are currently two pilot sites in the world where CO2 is injected into basalt containing aquifers. The first, the BSCSP Project, is in the United States in the state of Washington – it began in 2008, but is currently encountering operational problems.

22The second project is located in Iceland (90 % basalt), a country that is comparable with New Caledonia in terms of number of inhabitants. This demonstration project, known as the Hellisheidi CO2 Injection Pilot Study, is financed by Reykjavik Energy which provides for a research consortium made up of Icelandic, North American and French (LMTG, Toulouse) laboratories. The CO2 from a geothermal power plant is reinjected, in a form where it is dissolves in cold water, into basalt at a depth of 400 to 800 m reusing exploratory bores. The plan is, starting in August 2009, to inject 32 000 tonnes of CO2 each year into this natural laboratory. If it proves effective, the technology could be exported to other basalt regions in the world.

23The technology could, of course, find application in New Caledonia which has a large area of basalt across the northern half of the west coast. It should be noted that the Koniambo (KNS) project is located very close to areas covered with basalt.

Sequestration in peridotite

24Research conducted here is far less advanced than in the case of basalt, probably because the world’s peridotite masses are much smaller. There is still no pilot project, but recent scientific discoveries by the Lamont–Doherty Earth Observatory at the University of Columbia (New York, United States) into the peridotite masses in Oman demonstrate high potential for mineral sequestration using ultrabasic rocks. Researchers estimate that a carbonation process at a depth of 3 km, which would be highly economic following initialisation, would enable up to 1 Gt of CO2 per annum to be stored in Oman’s peridotite. They also insist that there is potential in the peridotite in New Caledonia and Papua New Guinea which, as in Oman, extends into the sea under a thin layer of sediment and is accessible down to a depth of 3 km. It is clear that this process will require a pilot site to be developed in one of these three regions of the world. We should add that, in comparison with mineral sequestration ex situ, this option requires less energy, does not require the transportation of any equipment (rocks) and could thus prove to be more cost-effective.

25Here too, New Caledonia has certain advantages: after Oman, it has the second biggest mass of peridotite in the world which is accessible down to a depth of 3 km in an area where the process put forward by the University of Columbia could be applied.

HOW CAN NEW CALEDONIA MAKE THE MOST OF ITS GEOLOGICAL POSITION?

Geological sequestration in sedimentary basins

26There is no experience in oil and gas operations in New Caledonia, but there is real potential in storage sites in the sedimentary basins on its west coast and deep off shore economic exclusive zone. It is highly probable that exploratory activities will be carried out in the medium and short-term. These activities will involve drilling which could uncover hydrocarbon reserves or, in the worst case scenario, saline aquifers.

27If reserves are found, CO2 could be stored during enhanced oil recovery and/or in the saline aquifers which touch hydrocarbons. New Caledonia must be prepared to negotiate this geological storage option with the international oil companies as soon as exploratory activities commence in its economic exclusive zone. Storage in saline aquifers will require a demonstration phase and any projects may call on European funding and international labelisation (IEA). Australia’s CO2CRC could be an excellent partner to lead this research, in particular on the Lord Howe ridge which is the target of joint exploration between Australia and New Caledonia.

28Prior to this, New Caledonia can continue to promote the oil potential of its sedimentary basins along with their potential in terms of the geological storage of CO2 which may be of interest to neighbouring countries. New Caledonia’s geological bureau (Dimenc), which has been very successful in exploiting economic interest in its sedimentary basins, should include this added-value in its promotional campaigns. As part of this, it could integrate French (Club CO2), European (CO2GeoNet) and Asia Pacific (Australia’s CO2CRS) international research networks.

29The most attractive sedimentary basis from an economic point of view are the basins on the west coast since these are relatively close to the CO2 emissions sites, and easily accessible. The Gouaro anticline, which has already been drilled, could be an interesting target for storage despite a discouraging evaluation in terms of oil. A lower cost study, in collaboration with the IFP and BRGM which are global specialists in this area, could be considered to revise and summarise the data obtained to-date and develop predictive storage models.

30In the case of off shore storage targets, problems remain in relation to distance and the costs of drilling. According to the IPCC, the distance of the CO2 emissions sites is, however, still reasonable if it does not exceed 300 km. Installations, and methods of transporting CO2 in liquid form by sea, are therefore conceivable.

In situ mineral sequestration in basalt

31In situ mineral sequestration in basalt is feasible in New Caledonia given that a large basalt unit stretches along the northern half of the west coast of Grande Terre. The results from pilot sites in North America (BSCSP Project) and Iceland (Hellisheidi CO2 Injection Pilot Study) will be needed to ascertain whether this process can be exported to New Caledonia. In the meantime, it would be wise to start by evaluating the potential of the basalt on the west coast of Grande Terre by means of laboratory experiments. This type of research is in proportion to funding put forward by the National Research Agency (ANR) “CO2 capture and storage” programme which is soon to reis-sue a call for tenders for CO2 sequestration. This project could involve Dimenc, the University of New Caledonia, BRGM, IFP and French research laboratories such as LMTG (University of Toulouse) which lead in this area. These will have to work with financial support from groups such as Eramet and Xstrata.

32In terms of the maturity of these processes, the “basalt” option falls between the “sedimentary basins” option which is already operational in certain circumstances and the “peridotite” option which is still at the research stage and awaits a pilot site. One of the advantages of sequestration in basalt is that drilling needs to be less deep (400-800 m) than with peridotite sequestration (3 000 m). A second advantage is that the planned Koniambo (project KNS) power plant is very close to the basalt coverage. Given the North Province’s concern with environmental problems, this solution is likely to be of great interest to the planned Koniambo power station which could integrate CO2 capture and storage, as well as to the Xstrata group which holds 49 % of the shares in the Koniambo project, is a partner to Australia’s CO2CRC, and is already involved in research into CO2 storage in the region. Elsewhere, the group has already invested 30 million dollars in the Otway Pilot Project in Australia.

In situ mineral sequestration in peridotite

33In situ mineral sequestration in peridotite is the most appealing storage option at the research and experimentation level. Even though researchers have reached a stage of maturity that is far less advanced than the “sedimentary basins” option, if this process proves to be reliable and effective, New Caledonia will be in a prime position globally to benefit from it. This operation could even prove less costly than the other options. The storage capacity demonstrated by the University of Columbia in the peridotite in Oman is comparable with that in New Caledonia. As the researchers highlight, all that is missing is a natural laboratory to move from the research to the demonstration stage.

34Given its geological position and CO2 emissions sites, New Caledonia has all the conditions in place to develop a collaborative pilot site comparable to the one at Hellisheidi in Iceland. This pilot project needs to take place on the coast of Grande Terre according to specialists at the University of Columbia who recommend drilling at sea to locate storage zones in peridotite at a depth of 3 km. Geophysical marine activities have already demonstrated the existence of peridotite masses along the coast and in Loyalty Basin. Any such project would need to be financed by the government and the industries responsible for CO2 emissions as is the case in Australia. At the European level, electricity companies that produce CO2 have had no hesitation in becoming involved and co-funding work throughout the capture and sequestration chain.

35A CO2 sequestration pilot project in the peridotite on Grande Terre would thus provide an opportunity to again develop New Caledonia’s geological situation and bring a new experimental site (the world’s third for in situ mineral sequestration, and the first in peridotite) to international research networks. The absence of petrophysical and geophysical data regarding these formations currently makes it tricky to estimate the true volume of their CO2 storage capacity. As with basalt, initial studies will need to be undertaken via ANR (National Research Agency) invitations to tender.

INTEREST IN CO2 STORAGE IN AUSTRALIA

36Along with the United States, Canada, Europe and Japan, Australia is one of five major centres conducting research into geological storage. Australia has made CCS (Carbon Capture and Storage) a national priority and created the CO2CRC (The Cooperative Research Centre for Greenhouse Gas Technologies), a joint-venture between industry, government, universities and research centres in Australia and abroad. The aim of this research is the reduce CCS costs and demonstrate its reliability and effectiveness, particularly in Australia and New Zealand. From the various CO2 elimination options, Australia has opted for geological storage in sedimentary basins on land, or close to its coasts. The country hopes to be at the forefront, and to export its expertise in this area.

37Australia has been running an operational pilot project – the CO2CRC Otway Project -since 2008; it is deemed to be one of the most illustrative in the world, and will see 100 000 tonnes of CO2 injected into a depleted gas reserve over two years; it also includes a major monitoring programme. Total has just kicked off with the same type of operation in the French Pyrenees (the Lacq reserve). At the same time, two other geological storage projects which have reached maturity are soon to be launched in Australia. The first Australian “clean coal” project by ZeroGen is a demonstration project on the east coast which will capture the CO2 produced from the gasification of coal and transport it by means of a 220 km pipeline to a geological storage site closer to the interior (project start planned for 2012). On the west coast, an industrial LNG project (the Gorgon Project), planned by Chevron, Shell and Exxon, is to inject 3.3 million tonnes of CO2 annually into a saline aquifer close to Barrow Island, which equates to a total of 125 million tonnes over the entire course of the project; the installation construction phase is to start at the end of 2009 and will last 5 years.

38Australia is thus making considerable investment in research and development projects regarding the geological storage of CO2 in sedimentary basins, and is becoming a global leader in this area. New Caledonia should thus have every interest in joining the CO2CRC network in which New Zealand is also heavily involved. While the level of knowledge is far less advanced, the sedimentary basins on the western coast of New Caledonia are still of certain interest in terms of geological storage in the same way as the Australian basins.

39As part of probable oil-related exploratory activities to be carried out on the Lord Howe Ridge, which extends across Australia’s and New Caledonia’s economic exclusive zone, the CO2CRC will certainly be interested in evaluating the possibilities of CO2 storage.

SHOULD NEW CALEDONIA’S EXPERIENCE IN CO2 MINERAL SEQUESTRATION BE SHARED?

40CCS is a planetary challenge in which France is keen to play a major role in terms of organising research and promoting technological solutions. If New Caledonia develops a pilot site for CO2 sequestration in peridotite, the results of its work will form a point of reference which will benefit the various international and industrial research teams.

41Expertise could be exported to Oman in particular where peridotite could store the CO2 emitted by the new electrical power plants which run on natural gas from the Gulf. The western coast of the United States is also interested in this storage option as demonstrated in work done by the University of Columbia. Papua New Guinea has peridotite massifs comparable with those in Oman and New Caledonia in terms of their surface area and tectonic context (peridotite in the sea below a thin layer of sediment enabling storage areas to be accessed down to a depth of 3 km): the island could, in the same way, consider this sequestration option when the time is right. Finally, other regions of the world such as the Balkans also boast large peridotite massifs.

CONCLUSION

42Given its geological situation, New Caledonia has the option to invest in three avenues of research into CO2 sequestration.

  • The sedimentary basins option: the sedimentary basins on the west coast of Grande Terre probably represent easily accessible storage targets (saline aquifers, undiscovered hydrocarbon deposits) close to CO2 emissions centres. Researchers will need to work with the oil industry and will thus be dependent on exploration into these basins being resumed. Such exploration may be carried out in partnership with the Australian CO2CRC network which specialises in this type of sequestration by establishing demonstration sites and, in the near future, commercial projects in the sedimentary basins along the coast of Australia.
  • The mineral sequestration option in basalt: would be of particular interest for the Koniambo (KNS) project located not far from these basic rock deposits. The results from the two demonstration sites in North America and Iceland will be needed before the reliability of the process can be confirmed. In the meantime, preliminary studies could be conducted to study the potential of the basalt on the west coast (field and laboratory studies).
  • Establishment of a collaborative mineral sequestration in peridotite pilot site is feasible, and would place New Caledonia at the forefront of the international scene. This site would have to be located on the east coast to achieve optimum sequestration conditions (storage in peridotite at a depth of 3 km). This would be the world’s third in situ mineral sequestration demonstration site, and the first in peridotite. If this process proves reliable and effective, the expertise could be exported to several regions throughout the world, and to Oman in particular where the oil industry is establishing natural gas powered electricity generating plants.

List of illustrations

Caption Figure 10 Geological map of New Caledonia by Pierre Maurizot, BRGM-Dimenc, 2001The belt of peridotite forms a third of the surface area of Grande Terre which is located close the centre of CO2 emissions. The unit of Poya, which stretches along a large section of the western coast, is made up primarily of basalt (95 %) which also supports CO2 storage.
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