Safe storage and effective monitoring of CO 2 in depleted gas fields
Carbon capture and storage (CCS) is vital to reduce CO 2 emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely availab...
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| creator | Jenkins, Charles R. Cook, Peter J. Ennis-King, Jonathan Undershultz, James Boreham, Chris Dance, Tess de Caritat, Patrice Etheridge, David M. Freifeld, Barry M. Hortle, Allison Kirste, Dirk Paterson, Lincoln Pevzner, Roman Schacht, Ulrike Sharma, Sandeep Stalker, Linda Urosevic, Milovan |
| description | Carbon capture and storage (CCS) is vital to reduce CO
2
emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely available helps to reduce public concerns, which may otherwise block this technology. The Otway Project has provided verification of the underlying science of CO
2
storage in a depleted gas field, and shows that the support of all stakeholders can be earned and retained. Quantitative verification of long-term storage has been demonstrated. A direct measurement of storage efficiency has been made, confirming that CO
2
storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of CO
2
.
Recent public opposition has caused setbacks to high-profile onshore CCS projects in Europe, such as Shell’s Barendrecht project, and Vatenfell’s in the Altmark. However, the Otway Project demonstrates that this opposition is not inevitable. As a range of our results are published, they reemphasize that geological carbon storage is sufficiently well-understood, scientifically and technically, to be scaled up to its key role in combating global warming. It is particularly important to have demonstrated that monitoring techniques are practical and quantitatively adequate to ensure safety, protect financial and physical assets, and guarantee climate abatement. No single project can answer all questions or remove all doubts, but our measurement of capacity is an empirical finding that shows previous estimates to be well-founded: There is large, useful capacity, worldwide, in depleted gas reservoirs. Obstacles to using this capacity are more social and political than scientific or technical.
It is important to know the capacity of subsurface storage for CO
2
. The global volumetric pore space is large, but the realistic storage capacity is diminished by many practical factors such as depth, the presence of suitable sealing rocks, or distance from sources. In the case of depleted gas fields, an important factor is the ability of injected CO
2
to reoccupy the pore space formerly containing natural gas. The potential capacity in depleted gas fields has been estimated to be significant on a global scale (
5
). By monitoring the rate of filling as we injected CO
2
into the Naylor field, we made an initial direct measurement of this i |
| doi_str_mv | 10.1073/pnas.1107255108 |
| format | Article |
| fullrecord | <record><control><sourceid>crossref</sourceid><recordid>TN_cdi_crossref_primary_10_1073_pnas_1107255108</recordid><sourceformat>XML</sourceformat><sourcesystem>PC</sourcesystem><sourcerecordid>10_1073_pnas_1107255108</sourcerecordid><originalsourceid>FETCH-LOGICAL-c1278-b8a6be89151c6ab15955a92509c3dba1952035db09823ab8e6c6d75b8a3e314d3</originalsourceid><addsrcrecordid>eNpFkEtLxDAUhYMoWEfXbvMHOnNv0rTJUuoTBmahrkseN6XSaUtTBP-9HRRmdQ4cvrP4GLtH2CJUcjcNNm1xrUIpBH3BMgSDeVkYuGQZgKhyXYjimt2k9AUARmnI2OO7jcTTMs62JW6HwClG8kv3Tfw4Dt06dEPLx8jrAxe8G3igqaeFAm9t4rGjPqRbdhVtn-juPzfs8_npo37N94eXt_phn3sUlc6dtqUjbVChL61DZZSyRigwXgZn0SgBUgUHRgtpnabSl6FSKyZJYhHkhu3-fv08pjRTbKa5O9r5p0FoThKak4TmLEH-Apl6Twg</addsrcrecordid><sourcetype>Aggregation Database</sourcetype><iscdi>true</iscdi><recordtype>article</recordtype></control><display><type>article</type><title>Safe storage and effective monitoring of CO 2 in depleted gas fields</title><source>Jstor Complete Legacy</source><source>PubMed Central</source><source>Alma/SFX Local Collection</source><source>Free Full-Text Journals in Chemistry</source><creator>Jenkins, Charles R. ; Cook, Peter J. ; Ennis-King, Jonathan ; Undershultz, James ; Boreham, Chris ; Dance, Tess ; de Caritat, Patrice ; Etheridge, David M. ; Freifeld, Barry M. ; Hortle, Allison ; Kirste, Dirk ; Paterson, Lincoln ; Pevzner, Roman ; Schacht, Ulrike ; Sharma, Sandeep ; Stalker, Linda ; Urosevic, Milovan</creator><creatorcontrib>Jenkins, Charles R. ; Cook, Peter J. ; Ennis-King, Jonathan ; Undershultz, James ; Boreham, Chris ; Dance, Tess ; de Caritat, Patrice ; Etheridge, David M. ; Freifeld, Barry M. ; Hortle, Allison ; Kirste, Dirk ; Paterson, Lincoln ; Pevzner, Roman ; Schacht, Ulrike ; Sharma, Sandeep ; Stalker, Linda ; Urosevic, Milovan</creatorcontrib><description>Carbon capture and storage (CCS) is vital to reduce CO
2
emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely available helps to reduce public concerns, which may otherwise block this technology. The Otway Project has provided verification of the underlying science of CO
2
storage in a depleted gas field, and shows that the support of all stakeholders can be earned and retained. Quantitative verification of long-term storage has been demonstrated. A direct measurement of storage efficiency has been made, confirming that CO
2
storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of CO
2
.
Recent public opposition has caused setbacks to high-profile onshore CCS projects in Europe, such as Shell’s Barendrecht project, and Vatenfell’s in the Altmark. However, the Otway Project demonstrates that this opposition is not inevitable. As a range of our results are published, they reemphasize that geological carbon storage is sufficiently well-understood, scientifically and technically, to be scaled up to its key role in combating global warming. It is particularly important to have demonstrated that monitoring techniques are practical and quantitatively adequate to ensure safety, protect financial and physical assets, and guarantee climate abatement. No single project can answer all questions or remove all doubts, but our measurement of capacity is an empirical finding that shows previous estimates to be well-founded: There is large, useful capacity, worldwide, in depleted gas reservoirs. Obstacles to using this capacity are more social and political than scientific or technical.
It is important to know the capacity of subsurface storage for CO
2
. The global volumetric pore space is large, but the realistic storage capacity is diminished by many practical factors such as depth, the presence of suitable sealing rocks, or distance from sources. In the case of depleted gas fields, an important factor is the ability of injected CO
2
to reoccupy the pore space formerly containing natural gas. The potential capacity in depleted gas fields has been estimated to be significant on a global scale (
5
). By monitoring the rate of filling as we injected CO
2
into the Naylor field, we made an initial direct measurement of this important parameter in CO
2
storage. Although dependent on detailed circumstances, for example, rock type or when storage begins after production ceases, our data adds weight to the conclusion that depleted gas fields have enough storage capacity to make a significant contribution to reducing global emissions.
Repeated seismic surveys attained a sensitivity that would have detected small leakages into deep aquifers just above the storage reservoir. Atmospheric monitoring demonstrated sensitivity at usefully small rates. Direct fluid sampling at the Naylor well showed good agreement between the predicted and observed CO
2
concentrations as the injected gas accumulated at the apex of the reservoir. A sustained program of monitoring of shallow potable aquifers and of soil gas content over the injection zone showed no anomalies. Although it is not logically possible to demonstrate no leakage, we showed how to quantify our nondetection of anomalies, thus demonstrating that undesirable levels of leakage could be detected in large-scale storage projects.
The monitoring of storage is a unique aspect of CCS that requires multidisciplinary skills. Clearly, there are basic safety issues associated with large volumes of CO
2
, but monitoring for immediately hazardous leakage is unproblematic. However, large-scale CCS deployment depends on associated financial rewards that will require monitoring over longer periods. Slow leakages into potable aquifers or the root zone are also concerns. Finally, CCS will be worse than useless if the stored CO
2
escapes back into the atmosphere, even very slowly, and leakage rates of less than 10% per thousand years are required for long-lasting climate benefits (
4
). The Otway Project explored a comprehensive suite of monitoring techniques and showed that the necessary degree of quantification is within reach.
Ultimately, key performance indicators were agreed upon with the state Environmental Protection Agency, and the injection well was drilled, surface and downhole equipment was installed, and injection of naturally occurring CO
2
/CH
4
from the nearby Buttress field commenced on March 18, 2008. Between March 2008 and August 2009, 65,445 t were stored, after which injection ceased. The storage site was the 2-km deep Naylor reservoir, from which natural gas had been commercially produced from 2002 to 2003. The CO
2
was injected about 300 m from the apex of the Naylor structure, and migrated under buoyancy over 4 mo to pool under the remaining natural gas. The original extraction well was reinstrumented to observe this process and recover samples of fluids as the CO
2
arrived, displacing water and natural gas.
Most aspects of this process are well-known in the oil and gas industry, but experience with CO
2
is relatively limited, and political sensitivities mandate caution. Consequently, our modeling and risk assessments dealt explicitly with probabilities, which in turn had to be communicated to stakeholders so that permissions and associated regulation could be established. A sustained and structured program of engagement with the local community was pursued throughout this phase of the project (
3
).
To demonstrate storage on a significant scale, public consent must be secured: The lesson learned from other international projects is that public opposition can easily escalate and be fatal to the project, and has cumulative effects on the vulnerability of other projects. The regulatory environment must be clearly understood, and if not comprehensive, additional permits may have to be negotiated. The best possible model of the relevant geology must be assembled, and the eventual fate of the injected CO
2
must be simulated. Knowledge of the deep subsurface is always incomplete, so it is crucial to consider a range of cases that bound possibilities. Risk assessment can commence once models are developed, based partly on empirical information and partly on expert judgment; if the risks are low or manageable, construction of the infrastructure to inject the CO
2
can begin.
The Otway Project is located in the state of Victoria, Australia, about 200 km west of Melbourne in the Otway Basin. The project’s objective was to be a pathfinder for CCS in Australia, developing a range of techniques for monitoring storage and setting an international example of transparency and accountability. The choice of a depleted gas field was partly motivated by the significant global capacity that was thought to be available in these structures. The project area is fairly prosperous dairy farming country, with good rainfall and dense settlement by Australian rural standards (
Fig. P1
).
Fig. P1.
The Otway Project’s injection well CRC-1, pictured in spring amongst the numerous small fields of the surrounding dairy farming area. This view is looking north toward the Buttress source well and the atmospheric monitoring towers, about 1 km distant.
Although increasing atmospheric CO
2
levels will cause climate changes that pose serious risks to humanity, fossil fuels will evidently continue to be used for decades (
1
). Large-scale carbon capture and storage (CCS) will be needed to meet this challenge (
2
). Despite the success of several industrial CCS projects, this technology (particularly storage) is controversial and seen as risky by some of the public. Open and transparent demonstration storage projects are critical both because they test scientific understanding and expectations, and also place processes, procedures, and regulations within the space of public discussion. The Otway Project successfully demonstrated midscale storage within a depleted gas field. Our measurement of its storage efficiency provides important physical confirmation of theoretical estimates that depleted gas fields could safely and effectively store many decades worth of CO
2
from the world’s largest point sources.</description><identifier>ISSN: 0027-8424</identifier><identifier>EISSN: 1091-6490</identifier><identifier>DOI: 10.1073/pnas.1107255108</identifier><language>eng</language><ispartof>Proceedings of the National Academy of Sciences - PNAS, 2012-01, Vol.109 (2)</ispartof><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c1278-b8a6be89151c6ab15955a92509c3dba1952035db09823ab8e6c6d75b8a3e314d3</citedby><cites>FETCH-LOGICAL-c1278-b8a6be89151c6ab15955a92509c3dba1952035db09823ab8e6c6d75b8a3e314d3</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,776,780,27903,27904</link.rule.ids></links><search><creatorcontrib>Jenkins, Charles R.</creatorcontrib><creatorcontrib>Cook, Peter J.</creatorcontrib><creatorcontrib>Ennis-King, Jonathan</creatorcontrib><creatorcontrib>Undershultz, James</creatorcontrib><creatorcontrib>Boreham, Chris</creatorcontrib><creatorcontrib>Dance, Tess</creatorcontrib><creatorcontrib>de Caritat, Patrice</creatorcontrib><creatorcontrib>Etheridge, David M.</creatorcontrib><creatorcontrib>Freifeld, Barry M.</creatorcontrib><creatorcontrib>Hortle, Allison</creatorcontrib><creatorcontrib>Kirste, Dirk</creatorcontrib><creatorcontrib>Paterson, Lincoln</creatorcontrib><creatorcontrib>Pevzner, Roman</creatorcontrib><creatorcontrib>Schacht, Ulrike</creatorcontrib><creatorcontrib>Sharma, Sandeep</creatorcontrib><creatorcontrib>Stalker, Linda</creatorcontrib><creatorcontrib>Urosevic, Milovan</creatorcontrib><title>Safe storage and effective monitoring of CO 2 in depleted gas fields</title><title>Proceedings of the National Academy of Sciences - PNAS</title><description>Carbon capture and storage (CCS) is vital to reduce CO
2
emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely available helps to reduce public concerns, which may otherwise block this technology. The Otway Project has provided verification of the underlying science of CO
2
storage in a depleted gas field, and shows that the support of all stakeholders can be earned and retained. Quantitative verification of long-term storage has been demonstrated. A direct measurement of storage efficiency has been made, confirming that CO
2
storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of CO
2
.
Recent public opposition has caused setbacks to high-profile onshore CCS projects in Europe, such as Shell’s Barendrecht project, and Vatenfell’s in the Altmark. However, the Otway Project demonstrates that this opposition is not inevitable. As a range of our results are published, they reemphasize that geological carbon storage is sufficiently well-understood, scientifically and technically, to be scaled up to its key role in combating global warming. It is particularly important to have demonstrated that monitoring techniques are practical and quantitatively adequate to ensure safety, protect financial and physical assets, and guarantee climate abatement. No single project can answer all questions or remove all doubts, but our measurement of capacity is an empirical finding that shows previous estimates to be well-founded: There is large, useful capacity, worldwide, in depleted gas reservoirs. Obstacles to using this capacity are more social and political than scientific or technical.
It is important to know the capacity of subsurface storage for CO
2
. The global volumetric pore space is large, but the realistic storage capacity is diminished by many practical factors such as depth, the presence of suitable sealing rocks, or distance from sources. In the case of depleted gas fields, an important factor is the ability of injected CO
2
to reoccupy the pore space formerly containing natural gas. The potential capacity in depleted gas fields has been estimated to be significant on a global scale (
5
). By monitoring the rate of filling as we injected CO
2
into the Naylor field, we made an initial direct measurement of this important parameter in CO
2
storage. Although dependent on detailed circumstances, for example, rock type or when storage begins after production ceases, our data adds weight to the conclusion that depleted gas fields have enough storage capacity to make a significant contribution to reducing global emissions.
Repeated seismic surveys attained a sensitivity that would have detected small leakages into deep aquifers just above the storage reservoir. Atmospheric monitoring demonstrated sensitivity at usefully small rates. Direct fluid sampling at the Naylor well showed good agreement between the predicted and observed CO
2
concentrations as the injected gas accumulated at the apex of the reservoir. A sustained program of monitoring of shallow potable aquifers and of soil gas content over the injection zone showed no anomalies. Although it is not logically possible to demonstrate no leakage, we showed how to quantify our nondetection of anomalies, thus demonstrating that undesirable levels of leakage could be detected in large-scale storage projects.
The monitoring of storage is a unique aspect of CCS that requires multidisciplinary skills. Clearly, there are basic safety issues associated with large volumes of CO
2
, but monitoring for immediately hazardous leakage is unproblematic. However, large-scale CCS deployment depends on associated financial rewards that will require monitoring over longer periods. Slow leakages into potable aquifers or the root zone are also concerns. Finally, CCS will be worse than useless if the stored CO
2
escapes back into the atmosphere, even very slowly, and leakage rates of less than 10% per thousand years are required for long-lasting climate benefits (
4
). The Otway Project explored a comprehensive suite of monitoring techniques and showed that the necessary degree of quantification is within reach.
Ultimately, key performance indicators were agreed upon with the state Environmental Protection Agency, and the injection well was drilled, surface and downhole equipment was installed, and injection of naturally occurring CO
2
/CH
4
from the nearby Buttress field commenced on March 18, 2008. Between March 2008 and August 2009, 65,445 t were stored, after which injection ceased. The storage site was the 2-km deep Naylor reservoir, from which natural gas had been commercially produced from 2002 to 2003. The CO
2
was injected about 300 m from the apex of the Naylor structure, and migrated under buoyancy over 4 mo to pool under the remaining natural gas. The original extraction well was reinstrumented to observe this process and recover samples of fluids as the CO
2
arrived, displacing water and natural gas.
Most aspects of this process are well-known in the oil and gas industry, but experience with CO
2
is relatively limited, and political sensitivities mandate caution. Consequently, our modeling and risk assessments dealt explicitly with probabilities, which in turn had to be communicated to stakeholders so that permissions and associated regulation could be established. A sustained and structured program of engagement with the local community was pursued throughout this phase of the project (
3
).
To demonstrate storage on a significant scale, public consent must be secured: The lesson learned from other international projects is that public opposition can easily escalate and be fatal to the project, and has cumulative effects on the vulnerability of other projects. The regulatory environment must be clearly understood, and if not comprehensive, additional permits may have to be negotiated. The best possible model of the relevant geology must be assembled, and the eventual fate of the injected CO
2
must be simulated. Knowledge of the deep subsurface is always incomplete, so it is crucial to consider a range of cases that bound possibilities. Risk assessment can commence once models are developed, based partly on empirical information and partly on expert judgment; if the risks are low or manageable, construction of the infrastructure to inject the CO
2
can begin.
The Otway Project is located in the state of Victoria, Australia, about 200 km west of Melbourne in the Otway Basin. The project’s objective was to be a pathfinder for CCS in Australia, developing a range of techniques for monitoring storage and setting an international example of transparency and accountability. The choice of a depleted gas field was partly motivated by the significant global capacity that was thought to be available in these structures. The project area is fairly prosperous dairy farming country, with good rainfall and dense settlement by Australian rural standards (
Fig. P1
).
Fig. P1.
The Otway Project’s injection well CRC-1, pictured in spring amongst the numerous small fields of the surrounding dairy farming area. This view is looking north toward the Buttress source well and the atmospheric monitoring towers, about 1 km distant.
Although increasing atmospheric CO
2
levels will cause climate changes that pose serious risks to humanity, fossil fuels will evidently continue to be used for decades (
1
). Large-scale carbon capture and storage (CCS) will be needed to meet this challenge (
2
). Despite the success of several industrial CCS projects, this technology (particularly storage) is controversial and seen as risky by some of the public. Open and transparent demonstration storage projects are critical both because they test scientific understanding and expectations, and also place processes, procedures, and regulations within the space of public discussion. The Otway Project successfully demonstrated midscale storage within a depleted gas field. Our measurement of its storage efficiency provides important physical confirmation of theoretical estimates that depleted gas fields could safely and effectively store many decades worth of CO
2
from the world’s largest point sources.</description><issn>0027-8424</issn><issn>1091-6490</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2012</creationdate><recordtype>article</recordtype><recordid>eNpFkEtLxDAUhYMoWEfXbvMHOnNv0rTJUuoTBmahrkseN6XSaUtTBP-9HRRmdQ4cvrP4GLtH2CJUcjcNNm1xrUIpBH3BMgSDeVkYuGQZgKhyXYjimt2k9AUARmnI2OO7jcTTMs62JW6HwClG8kv3Tfw4Dt06dEPLx8jrAxe8G3igqaeFAm9t4rGjPqRbdhVtn-juPzfs8_npo37N94eXt_phn3sUlc6dtqUjbVChL61DZZSyRigwXgZn0SgBUgUHRgtpnabSl6FSKyZJYhHkhu3-fv08pjRTbKa5O9r5p0FoThKak4TmLEH-Apl6Twg</recordid><startdate>20120110</startdate><enddate>20120110</enddate><creator>Jenkins, Charles R.</creator><creator>Cook, Peter J.</creator><creator>Ennis-King, Jonathan</creator><creator>Undershultz, James</creator><creator>Boreham, Chris</creator><creator>Dance, Tess</creator><creator>de Caritat, Patrice</creator><creator>Etheridge, David M.</creator><creator>Freifeld, Barry M.</creator><creator>Hortle, Allison</creator><creator>Kirste, Dirk</creator><creator>Paterson, Lincoln</creator><creator>Pevzner, Roman</creator><creator>Schacht, Ulrike</creator><creator>Sharma, Sandeep</creator><creator>Stalker, Linda</creator><creator>Urosevic, Milovan</creator><scope>AAYXX</scope><scope>CITATION</scope></search><sort><creationdate>20120110</creationdate><title>Safe storage and effective monitoring of CO 2 in depleted gas fields</title><author>Jenkins, Charles R. ; Cook, Peter J. ; Ennis-King, Jonathan ; Undershultz, James ; Boreham, Chris ; Dance, Tess ; de Caritat, Patrice ; Etheridge, David M. ; Freifeld, Barry M. ; Hortle, Allison ; Kirste, Dirk ; Paterson, Lincoln ; Pevzner, Roman ; Schacht, Ulrike ; Sharma, Sandeep ; Stalker, Linda ; Urosevic, Milovan</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c1278-b8a6be89151c6ab15955a92509c3dba1952035db09823ab8e6c6d75b8a3e314d3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2012</creationdate><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Jenkins, Charles R.</creatorcontrib><creatorcontrib>Cook, Peter J.</creatorcontrib><creatorcontrib>Ennis-King, Jonathan</creatorcontrib><creatorcontrib>Undershultz, James</creatorcontrib><creatorcontrib>Boreham, Chris</creatorcontrib><creatorcontrib>Dance, Tess</creatorcontrib><creatorcontrib>de Caritat, Patrice</creatorcontrib><creatorcontrib>Etheridge, David M.</creatorcontrib><creatorcontrib>Freifeld, Barry M.</creatorcontrib><creatorcontrib>Hortle, Allison</creatorcontrib><creatorcontrib>Kirste, Dirk</creatorcontrib><creatorcontrib>Paterson, Lincoln</creatorcontrib><creatorcontrib>Pevzner, Roman</creatorcontrib><creatorcontrib>Schacht, Ulrike</creatorcontrib><creatorcontrib>Sharma, Sandeep</creatorcontrib><creatorcontrib>Stalker, Linda</creatorcontrib><creatorcontrib>Urosevic, Milovan</creatorcontrib><collection>CrossRef</collection><jtitle>Proceedings of the National Academy of Sciences - PNAS</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Jenkins, Charles R.</au><au>Cook, Peter J.</au><au>Ennis-King, Jonathan</au><au>Undershultz, James</au><au>Boreham, Chris</au><au>Dance, Tess</au><au>de Caritat, Patrice</au><au>Etheridge, David M.</au><au>Freifeld, Barry M.</au><au>Hortle, Allison</au><au>Kirste, Dirk</au><au>Paterson, Lincoln</au><au>Pevzner, Roman</au><au>Schacht, Ulrike</au><au>Sharma, Sandeep</au><au>Stalker, Linda</au><au>Urosevic, Milovan</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Safe storage and effective monitoring of CO 2 in depleted gas fields</atitle><jtitle>Proceedings of the National Academy of Sciences - PNAS</jtitle><date>2012-01-10</date><risdate>2012</risdate><volume>109</volume><issue>2</issue><issn>0027-8424</issn><eissn>1091-6490</eissn><abstract>Carbon capture and storage (CCS) is vital to reduce CO
2
emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely available helps to reduce public concerns, which may otherwise block this technology. The Otway Project has provided verification of the underlying science of CO
2
storage in a depleted gas field, and shows that the support of all stakeholders can be earned and retained. Quantitative verification of long-term storage has been demonstrated. A direct measurement of storage efficiency has been made, confirming that CO
2
storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of CO
2
.
Recent public opposition has caused setbacks to high-profile onshore CCS projects in Europe, such as Shell’s Barendrecht project, and Vatenfell’s in the Altmark. However, the Otway Project demonstrates that this opposition is not inevitable. As a range of our results are published, they reemphasize that geological carbon storage is sufficiently well-understood, scientifically and technically, to be scaled up to its key role in combating global warming. It is particularly important to have demonstrated that monitoring techniques are practical and quantitatively adequate to ensure safety, protect financial and physical assets, and guarantee climate abatement. No single project can answer all questions or remove all doubts, but our measurement of capacity is an empirical finding that shows previous estimates to be well-founded: There is large, useful capacity, worldwide, in depleted gas reservoirs. Obstacles to using this capacity are more social and political than scientific or technical.
It is important to know the capacity of subsurface storage for CO
2
. The global volumetric pore space is large, but the realistic storage capacity is diminished by many practical factors such as depth, the presence of suitable sealing rocks, or distance from sources. In the case of depleted gas fields, an important factor is the ability of injected CO
2
to reoccupy the pore space formerly containing natural gas. The potential capacity in depleted gas fields has been estimated to be significant on a global scale (
5
). By monitoring the rate of filling as we injected CO
2
into the Naylor field, we made an initial direct measurement of this important parameter in CO
2
storage. Although dependent on detailed circumstances, for example, rock type or when storage begins after production ceases, our data adds weight to the conclusion that depleted gas fields have enough storage capacity to make a significant contribution to reducing global emissions.
Repeated seismic surveys attained a sensitivity that would have detected small leakages into deep aquifers just above the storage reservoir. Atmospheric monitoring demonstrated sensitivity at usefully small rates. Direct fluid sampling at the Naylor well showed good agreement between the predicted and observed CO
2
concentrations as the injected gas accumulated at the apex of the reservoir. A sustained program of monitoring of shallow potable aquifers and of soil gas content over the injection zone showed no anomalies. Although it is not logically possible to demonstrate no leakage, we showed how to quantify our nondetection of anomalies, thus demonstrating that undesirable levels of leakage could be detected in large-scale storage projects.
The monitoring of storage is a unique aspect of CCS that requires multidisciplinary skills. Clearly, there are basic safety issues associated with large volumes of CO
2
, but monitoring for immediately hazardous leakage is unproblematic. However, large-scale CCS deployment depends on associated financial rewards that will require monitoring over longer periods. Slow leakages into potable aquifers or the root zone are also concerns. Finally, CCS will be worse than useless if the stored CO
2
escapes back into the atmosphere, even very slowly, and leakage rates of less than 10% per thousand years are required for long-lasting climate benefits (
4
). The Otway Project explored a comprehensive suite of monitoring techniques and showed that the necessary degree of quantification is within reach.
Ultimately, key performance indicators were agreed upon with the state Environmental Protection Agency, and the injection well was drilled, surface and downhole equipment was installed, and injection of naturally occurring CO
2
/CH
4
from the nearby Buttress field commenced on March 18, 2008. Between March 2008 and August 2009, 65,445 t were stored, after which injection ceased. The storage site was the 2-km deep Naylor reservoir, from which natural gas had been commercially produced from 2002 to 2003. The CO
2
was injected about 300 m from the apex of the Naylor structure, and migrated under buoyancy over 4 mo to pool under the remaining natural gas. The original extraction well was reinstrumented to observe this process and recover samples of fluids as the CO
2
arrived, displacing water and natural gas.
Most aspects of this process are well-known in the oil and gas industry, but experience with CO
2
is relatively limited, and political sensitivities mandate caution. Consequently, our modeling and risk assessments dealt explicitly with probabilities, which in turn had to be communicated to stakeholders so that permissions and associated regulation could be established. A sustained and structured program of engagement with the local community was pursued throughout this phase of the project (
3
).
To demonstrate storage on a significant scale, public consent must be secured: The lesson learned from other international projects is that public opposition can easily escalate and be fatal to the project, and has cumulative effects on the vulnerability of other projects. The regulatory environment must be clearly understood, and if not comprehensive, additional permits may have to be negotiated. The best possible model of the relevant geology must be assembled, and the eventual fate of the injected CO
2
must be simulated. Knowledge of the deep subsurface is always incomplete, so it is crucial to consider a range of cases that bound possibilities. Risk assessment can commence once models are developed, based partly on empirical information and partly on expert judgment; if the risks are low or manageable, construction of the infrastructure to inject the CO
2
can begin.
The Otway Project is located in the state of Victoria, Australia, about 200 km west of Melbourne in the Otway Basin. The project’s objective was to be a pathfinder for CCS in Australia, developing a range of techniques for monitoring storage and setting an international example of transparency and accountability. The choice of a depleted gas field was partly motivated by the significant global capacity that was thought to be available in these structures. The project area is fairly prosperous dairy farming country, with good rainfall and dense settlement by Australian rural standards (
Fig. P1
).
Fig. P1.
The Otway Project’s injection well CRC-1, pictured in spring amongst the numerous small fields of the surrounding dairy farming area. This view is looking north toward the Buttress source well and the atmospheric monitoring towers, about 1 km distant.
Although increasing atmospheric CO
2
levels will cause climate changes that pose serious risks to humanity, fossil fuels will evidently continue to be used for decades (
1
). Large-scale carbon capture and storage (CCS) will be needed to meet this challenge (
2
). Despite the success of several industrial CCS projects, this technology (particularly storage) is controversial and seen as risky by some of the public. Open and transparent demonstration storage projects are critical both because they test scientific understanding and expectations, and also place processes, procedures, and regulations within the space of public discussion. The Otway Project successfully demonstrated midscale storage within a depleted gas field. Our measurement of its storage efficiency provides important physical confirmation of theoretical estimates that depleted gas fields could safely and effectively store many decades worth of CO
2
from the world’s largest point sources.</abstract><doi>10.1073/pnas.1107255108</doi><oa>free_for_read</oa></addata></record> |
| fulltext | fulltext |
| identifier | ISSN: 0027-8424 |
| ispartof | Proceedings of the National Academy of Sciences - PNAS, 2012-01, Vol.109 (2) |
| issn | 0027-8424 1091-6490 |
| language | eng |
| recordid | cdi_crossref_primary_10_1073_pnas_1107255108 |
| source | Jstor Complete Legacy; PubMed Central; Alma/SFX Local Collection; Free Full-Text Journals in Chemistry |
| title | Safe storage and effective monitoring of CO 2 in depleted gas fields |
| url | https://sfx.bib-bvb.de/sfx_tum?ctx_ver=Z39.88-2004&ctx_enc=info:ofi/enc:UTF-8&ctx_tim=2025-01-25T02%3A42%3A18IST&url_ver=Z39.88-2004&url_ctx_fmt=infofi/fmt:kev:mtx:ctx&rfr_id=info:sid/primo.exlibrisgroup.com:primo3-Article-crossref&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.genre=article&rft.atitle=Safe%20storage%20and%20effective%20monitoring%20of%20CO%202%20in%20depleted%20gas%20fields&rft.jtitle=Proceedings%20of%20the%20National%20Academy%20of%20Sciences%20-%20PNAS&rft.au=Jenkins,%20Charles%20R.&rft.date=2012-01-10&rft.volume=109&rft.issue=2&rft.issn=0027-8424&rft.eissn=1091-6490&rft_id=info:doi/10.1073/pnas.1107255108&rft_dat=%3Ccrossref%3E10_1073_pnas_1107255108%3C/crossref%3E%3Curl%3E%3C/url%3E&disable_directlink=true&sfx.directlink=off&sfx.report_link=0&rft_id=info:oai/&rft_id=info:pmid/&rfr_iscdi=true |