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Comments on Singh et al. (2022) ‘Marine seismic surveys for hydrocarbon exploration: What’s at stake?’

Authors:
Hayley C Cawthra at Council for Geoscience Western Cape office; Nelson Mandela University
Hayley C Cawthra
  • Council for Geoscience Western Cape office; Nelson Mandela University
Martin B.C. Brandt
Martin B.C. Brandt
Martin B.C. Brandt
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Nigel Hicks at Council for Geoscience
Nigel Hicks
David Khoza
David Khoza
David Khoza
  • This person is not on ResearchGate, or hasn't claimed this research yet.
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Abstract

SIGNIFICANCE: We write this Commentary as a reply to Singh et al.(S Afr J Sci. 118(3/4), Art. #13420). We found that Singh et al.'s article did not adequately cover a rounded viewpoint on the topic, and we highlight a different perspective, calling for a balanced review in this regard. We base our argument on two premises. First, the literature study is incomplete, which creates a misleading perception that nothing is currently being done in South Africa to transition to a low carbon economy. Second, we comment on the statements made on seismic surveys. Herewith, we request that the authors consider a corrigendum that better reflects this research space, and call for more discussion on this topic.
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1Volume 119| Number 3/4
March/April 2023
Commentary
https://doi.org/10.17159/sajs.2023/14514
© 2023. The Author(s). Published
under a Creative Commons
Attribution Licence.
Comments on Singh et al. (2022) ‘Marine seismic
surveys for hydrocarbon exploration: What’s
at stake?’
AUTHORS:
Hayley C. Cawthra1
Martin B.C. Brandt1
Nigel Hicks1
David Khoza1
AFFILIATION:
1Council for Geoscience, Pretoria,
South Africa
CORRESPONDENCE TO:
Hayley Cawthra
EMAIL:
hcawthra@geoscience.org.za
HOW TO CITE:
Cawthra HC, Brandt MBC, Hicks N,
Khoza D. Comments on Singh et al.
(2022) ‘Marine seismic surveys for
hydrocarbon exploration: What’s at
stake?’. S Afr J Sci. 2023;119(3/4),
Art. #14514. https://doi.
org/10.17159/sajs.2023/14514
ARTICLE INCLUDES:
☐ Peer review
☐ Supplementary material
KEYWORDS:
just energy transition, CO2 capture
and storage, seismic surveys, climate
change, marine life
PUBLISHED:
29 March 2023
Significance:
We write this Commentary as a reply to Singh et al.(S Afr J Sci. 118(3/4), Art. #13420). We found that
Singh et al.’s article did not adequately cover a rounded viewpoint on the topic, and we highlight a different
perspective, calling for a balanced review in this regard. We base our argument on two premises. First, the
literature study is incomplete, which creates a misleading perception that nothing is currently being done
in South Africa to transition to a low carbon economy. Second, we comment on the statements made on
seismic surveys. Herewith, we request that the authors consider a corrigendum that better reflects this
research space, and call for more discussion on this topic.
On the first concern, a statement in the paper1 suggests that only one programme aims to transition South Africa’s
economy to a low carbon emission future, and that this is a new initiative. This is not the case. The statement in
Singh et al.1 reads as follows:
In November 2021, the governments of South Africa, France, Germany, the United
Kingdom and the United States of America, along with the European Union, announced
a long-term ‘Just Energy Transition Partnership’ to support South Africa’s decarbonisation
efforts. The partnership will mobilise an initial commitment of USD8.5 billion for the rst
phase of nancing through various mechanisms including grants, concessional loans and
investments and risk sharing instruments. The Partnership aims to prevent up to 1–1.5
gigatonnes of emissions over the next 20 years and support South Africa’s move away
from coal and its accelerated transition to a low emission, climate resilient economy.
Although this is announcing a new project, we are aware of at least four ongoing programmes that focus on this
topic. These are discussed below:
1. Funding is provided by the World Bank for research into carbon sequestration and this builds on more than a
decade of work, thus far. The Council for Geoscience in collaboration with industry partners and government
compiled an atlas in 2010 on the geological storage of carbon dioxide in South Africa2, which identified
possible onshore and offshore repositories within South Africa conforming to the prerequisites for carbon
capture and storage. Since the publication of this atlas, research has expanded on three potential storage
basins, namely the onshore Zululand and Algoa Basins and the offshore Durban Basin3-9, with academic
research into the viability of the offshore Orange Basin currently ongoing. CO2 capture and storage is
globally recognised as one of the key technologies in a suite of emission reduction strategies to combat
anthropogenic climate change.10,11 CO2 capture and storage technologies linked with hydrocarbon exploitation
is not a new practice – companies such as Statoil in Norway have captured and stored 22 Mt of CO2 in
offshore saline aquifers since 199612, largely mitigating the long-term effects of greenhouse gas emissions
alluded to by Singh et al.1 Current research within South Africa8 indicates that individual sedimentary basins
possess multiple storage reservoirs with capacities equivalent to regions of the Rotliegend sandstone in
the North Sea13. This work is already under way and a next phase of study, or economic studies run in
parallel with geological investigations, may investigate the uncertainty surrounding sustainable injection
rates and to what extent storage infrastructure is feasible within a balanced energy mix (see for example
Lane et al.14). The technologies and practices associated with geological CO2 sequestration are all in current
commercial operation, and have been so for a decade to several decades. Such commercial operations
include enhanced oil recovery, acid gas (CO2) injection, natural gas storage and CO2 pipeline transportation.
No major ‘breakthrough’ technological innovations appear to be required for large-scale CO2 transportation
and storage. There are, however, significant policy, legal and regulatory challenges that must be resolved
before CO2 capture and storage is widely implemented.
2. A newly instated World Bank funded project is in progress in Leandra, Mpumalanga, where the feasibility of
injecting between 10 000 and 50 000 metric tons of CO2 (per year) into underground basaltic formations will
be tested in 2023, at a depth of at least 1 km below ground.15,16 As continental flood basalts represent some of
the largest geological structures on the planet, they have the potential to provide large volumes of CO2 storage
capacity to regions such as the Mpumalanga Province in South Africa, where sedimentary storage options are
limited. Due to the extensive nature of such geological substrates and their mineral trapping properties, they
represent important research focus points for meeting global CO2 emissions targets, as has been illustrated
through the Wallulah Project in the USA and Carbfix in Iceland.17,18
3. USAID and Power Africa are building a public–private partnership to improve access to clean electricity
and Internet connectivity at health facilities in sub-Saharan Africa, by supporting the development of 3180
megawatts of electricity generation in South Africa through solar and wind power installations.19
2Volume 119| Number 3/4
March/April 2023
Commentary
https://doi.org/10.17159/sajs.2023/14514
Comment on Singh et al. (2022)
Page 2 of 2
4. South African banks are also invested in this initiative to consider
the just energy transition. Nedbank’s funding for renewable energy
was established in 201520 and Investec’s investment in Green
Bonds since 202221.
Therefore, the message in the Singh et al. article1, namely that this has
not been considered in South Africa, is misleading.
On the matter of seismic surveys, we refer to two recently published
papers. In Kavanagh et al.’s22 ‘Seismic surveys reduce cetacean sightings
across a large marine ecosystem’, they emphasise the importance of
timing of seismic surveys to best mitigate against disturbance. These
authors provide results on localised avoidance in this regard and we
advocate for similar mitigation in planning these surveys in South African
waters, before attempting to halt all exploration activities. Additionally,
Carroll et al.’s23 ‘A critical review of the potential impacts of marine
seismic surveys on fish & invertebrates’ talks to the gap in knowledge
on sound thresholds and recovery of marine fish and invertebrates. They
caution against generalisations about airgun arrays among taxa until
more information is available to ensure scientific validity. We underscore
the importance of conducting a local study on measured harm or impact
that hydrocarbon exploration through seismic surveying imposes on
marine life, as this has not yet been done in South Africa. A rising demand
for minerals, metals and hydrocarbons, in tandem with a rapid depletion
of land-based resources and increasing global population, has led to a
surge of interest in blue economies and South Africa is no exception.
Therefore, finding a suitable balance between resource extraction and
environmental protection is likely a more feasible option than a call for
a moratorium on hydrocarbon exploration at this stage. The renewable
energy space relies on a different suite of metals, and perhaps because
those risks are less well understood, it seems a preferable compromise
but requires further research to better constrain the trade-off.
Through this reply, and the two broad points discussed above, we appeal
to Singh and colleagues1 and the South African science community to
consider a more representative literature study to present a complete
picture of the just transition, and not promote the one specific ‘Just
Energy Transition Partnership’ project. Furthermore, gaining a clearer
understanding of risks associated with alternative energy options is timely.
Competing interests
We have no competing interests to declare.
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ResearchGate has not been able to resolve any citations for this publication.
CO2 storage potential of basaltic rocks, Mpumalanga: Implications for the Just Transition
Article
Full-text available
  • Jul 2022
  • S AFR J SCI
South Africa is the largest CO2 emitter on the African continent. These emissions stem from a heavy reliance on coal as the primary energy fuel and contributor toward socio-economic development. The South African government has targeted reducing CO2 emissions by more than half in the next 10 years. To meet climate change mitigation scenarios, while alleviating continued emissions, South Africa will look to technologies such as carbon capture, utilisation and storage. Initial assessments of South Africa’s potential for CO2 storage have focused on deep saline aquifers within volcano-sedimentary sequences along the near and offshore regions. Sustaining the Just Transition will, however, require additional storage capacity. In this study, we make an initial assessment of possible CO2 storage in basaltic sequences of the Ventersdorp Supergroup. Geological and mineralogical information was ascertained from borehole data. The geological information suggests that the subsurface extent of the Ventersdorp Supergroup is at least 80 000 km² larger than previously mapped, extending beneath major point-source CO2 emitters and active coalfields. Furthermore, petrographic analyses suggest pore space of up to ca 15% with minimal alteration, and preservation of mafic silicate minerals that would enable reactive carbonation of injected CO2. Notable metasomatic and hydrothermal alteration is confined to significant contact horizons, such as the lowermost Ventersdorp Contact Reef. These results suggest that basaltic sequences may exponentially increase South Africa’s CO2 sequestration storage capacity and may have a significant impact on the country’s Just Transition. © 2022. The Author(s). Published under a Creative Commons Attribution Licence.
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Marine seismic surveys for hydrocarbon exploration: What's at stake?
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  • Mar 2022
The immediate, intermediate, and long-term implications of seismic surveys for hydrocarbon exploration merit noting. If seismic surveys detect feasible hydrocarbon deposits, they effectively serve as a precursor to hydrocarbon extraction and consumption. The additional greenhouse gas emissions that will originate from new oil and gas fields in South Africa will push the world closer to the tipping point of breaching the limit of 1.5 °C targeted at the 2021 COP26 UN climate summit, and should thus be avoided at all costs. South Africa’s pursuit of energy self-sufficiency through local fossil fuel extraction should not come at the cost of its unique biodiversity nor planetary health.
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Uncertain storage prospects create a conundrum for carbon capture and storage ambitions
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Grand hopes exist that carbon capture and storage can have a major decarbonization role at global, regional and sectoral scales. Those hopes rest on the narrative that an abundance of geological storage opportunity is available to meet all needs. In this Perspective, we present the contrasting view that deep uncertainty over the sustainable injection rate at any given location will constrain the pace and scale of carbon capture and storage deployment. Although such constraints will probably have implications in most world regions, they may be particularly relevant in major developing Asian economies. To minimize the risk that these constraints pose to the decarbonization imperative, we discuss steps that are urgently needed to evaluate, plan for and reduce the uncertainty over CO2 storage prospects.
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Seismic surveys reduce cetacean sightings across a large marine ecosystem
Article
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  • Dec 2019
Noise pollution is increasing globally, and as oceans are excellent conductors of sound, this is a major concern for marine species reliant on sound for key life functions. Loud, impulsive sounds from seismic surveys have been associated with impacts on many marine taxa including mammals, crustaceans, cephalopods, and fish. However, impacts across large spatial scales or multiple species are rarely considered. We modelled over 8,000 hours of cetacean survey data across a large marine ecosystem covering > 880,000 km2 to investigate the effect of seismic surveys on baleen and toothed whales. We found a significant effect of seismic activity across multiple species and habitats, with an 88% (82–92%) decrease in sightings of baleen whales, and a 53% (41–63%) decrease in sightings of toothed whales during active seismic surveys when compared to control surveys. Significantly fewer sightings of toothed whales also occurred during active versus inactive airgun periods of seismic surveys, although some species-specific response to noise was observed. This study provides strong evidence of multi-species impacts from seismic survey noise on cetaceans. Given the global proliferation of seismic surveys and large propagation distances of airgun noise, our results highlight the large-scale impacts that marine species are currently facing.
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A critical review of the potential impacts of marine seismic surveys on fish & invertebrates
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Marine seismic surveys produce high intensity, low-frequency impulsive sounds at regular intervals, with most sound produced between 10 and 300 Hz. Offshore seismic surveys have long been considered to be disruptive to fisheries, but there are few ecological studies that target commercially important species, particularly invertebrates. This review aims to summarise scientific studies investigating the impacts of low-frequency sound on marine fish and invertebrates, as well as to critically evaluate how such studies may apply to field populations exposed to seismic operations. We focus on marine seismic surveys due to their associated unique sound properties (i.e. acute, low-frequency, mobile source locations), as well as fish and invertebrates due to the commercial value of many species in these groups. The main challenges of seismic impact research are the translation of laboratory results to field populations over a range of sound exposure scenarios and the lack of sound exposure standardisation which hinders the identification of response thresholds. An integrated multidisciplinary approach to manipulative and in situ studies is the most effective way to establish impact thresholds in the context of realistic exposure levels, but if that is not practical the limitations of each approach must be carefully considered.
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Atlas on the geological storage of carbon dioxide in South Africa
Book
Full-text available
  • Jan 2010
In order to mitigate climate change, the world is moving towards ambitious goals for the reduction of carbon dioxide emissions. However, carbon dioxide emissions arise largely through the use of fossil fuels to provide energy that is, in turn, an essential ingredient for achieving economic and social development. Similar to the countries that rely heavily on their fossil fuel resources for energy, South Africa is exploring various ways to 'decarbonise' its energy supplies over the coming decades without compromising energy security. A number of opportunities for decarbonisation have been identified globally. These include improved energy efficiency, implementing cleaner coal technologies and the rapid deployment of renewable and nuclear energy. Each of these opportunities are being investigated in order to determine the extent to which they can contribute towards the mitigation of greenhouse gas emissions in South Africa. These opportunities have their unique challenges and all of the opportunities will need to be harnessed if the joint goals of climate change mitigation and energy security are to be achieved. Within the realm of cleaner coal technologies, the capture and storage of carbon dioxide — known as 'carbon capture and storage', or CCS — is proposed as a technology that has the potential to significantly reduce the carbon footprint of various types of fossil fuel-fired installations. There are a number of variants of this technology, depending on the source of the carbon dioxide and the type of storage available. Full-scale capture technologies for different sources are being investigated internationally; however, the type of storage available will depend mostly on local conditions. South Africa's emissions of carbon dioxide are currently estimated at over 400 Mt per annum, including both point and diffuse sources. It is apparent that South Africa will remain reliant on fossil fuels for the next few decades until other energy sources can gradually replace these high-carbon fuels. CCS is therefore regarded as a transition measure from fossil fuels to renewable/nuclear energies. Storage opportunities may be sought for smaller or shorter-term point sources, but also for larger or longer-term point sources. For example, a project that emits 1 Mt of carbon dioxide per year for 20 years would require proven storage in the order of 20 Mt (0.02 Gt), while a project that emits 30 Mt of carbon dioxide per year for 50 years would require proven storage of the order of 1 500 Mt (1.5 Gt). A previous study into South Africa's potential for storing carbon dioxide was undertaken at the behest of the then Department of Minerals and Energy by the CSIR and released during 2004. At a theoretical level, the study determined that South Africa could have substantial storage capacity in geological formations. This Atlas, funded by multiple stakeholders, was initiated in order to further define the geological storage capacity that can be found in South Africa. In the preparation of the Atlas, the Council for Geoscience and the Petroleum Agency of South Africa have utilised existing information, including seismic and historical drill-core data from the onshore and offshore sedimentary basins, in order to estimate the storage potential of depleted oil and gas reservoirs, deep and unmineable coal seams and deep saline formations. Part 1 of this Atlas provides an introduction to South Africa's energy economy and greenhouse gas emissions. Part 2 elaborates on the geological conditions required for successful storage and methods of estimation. Part 3 provides detailed insights for each of the three storage types that have been investigated. The theoretical potential identified by the earlier study for deep saline formations in the Karoo Supergroup has been confounded by the low permeability and porosity measurements obtained. In addition, the relatively small estimated storage capacities (at less than 1 Gt each) of depleted oil and gas reservoirs and deep, unmineable coal seams have been confirmed. Nonetheless, these areas may provide unique storage opportunities for smaller point sources. This Atlas has expanded on previous studies and identified new storage potential in the onshore and offshore Mesozoic basins that run along the coast of South Africa. In summary, the Atlas identifies approximately 150 Gt of potential storage in the three storage types (deep saline formations, unmineable coal seams and depleted oil and gas reservoirs) of which about 98% is offshore. These investigations also indicate that the Karoo Basin should be considered as non-conventional storage and requires further investigation before it could be considered a potential storage site. The Atlas indicates that a major portion of the storage is distant from current emission sources. Further techno-economic evaluations will be required in order to define the ultimate role of CCS in South Africa's energy mix. While this Atlas represents a significant advance on previous estimates, it is pertinent to draw attention to the question of certainty. Other atlases have developed a variety of indicators in order to reflect the relative confidence that can be placed in the data (and hence the estimated capacity calculations). This Atlas uses an indicator that yields confidence levels for the various estimates that range from 1 (low) to 9 (high). The uncertainty largely reflects the paucity of borehole data and seismic surveys. Significant investments will be required in order to realise the commercialisation of carbon capture and storage technology in South Africa. Investment decisions are likely to follow an iterative process between estimating the costs for matching sources to potential sinks and obtaining further geological information, as well as investing in alternative mitigation options. This last consideration really only applies in the shorter term, if one accepts the earlier assertion that all types of mitigation will be required in order to address both climate change mitigation and energy security. Overall, long time frames are required to characterise potential storage reservoirs, develop the necessary skills and technology base and to consult with the public. This Atlas is a key component of the programme that is intended to develop a full-scale CCS deployment beyond 2025.
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The CCS hub in Norway: some insights from 22 years of saline aquifer storage
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The development of industrial-scale CCS in Norway, starting with the Sleipner project in 1996, gives a uniquely long track record of experience with CCS and provides valuable insights for the projected global growth in CCS. By the end of 2017, the Sleipner and Snøhvit CCS projects had captured and stored 22 Mt of CO2 in saline aquifers offshore Norway. CO2 plume monitoring observations at Sleipner can be used to indicate an overall storage efficiency of around 5% of the pore volume, with approximately one tenth of this volume dissolved in the brine phase. These estimates are consistent with the fluid dynamics of CO2 injection in which a gravity dominated processes are expected to give efficiencies in the range of 1-6%. Future projects may be able to find ways of improving these efficiencies.
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A first assessment of potential stratigraphic traps for geological storage of CO 2 in the Durban Basin, South Africa
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  • Sep 2017
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Within offshore frontier sedimentary basins, legacy data are important tools in basin-scale exploration for potential CO2 storage. We utilise single-channel 2D seismic reflection and well data obtained from the offshore Durban Basin, east coast South Africa, to provide new evidence of reservoir/seal pairs in saline aquifers that may represent potential storage sites for CO2 injection. Multiple, previously undefined and regionally pervasive stratigraphic traps have been mapped through a detailed seismo-sedimentary analysis. These include shelf-bound shallow-marine-sheet and deltaic sandstone packages of Turonian and Maastrichtian age respectively. Coeval with these laterally extensive shelf packages, multiple basin floor fan systems have been identified on the palaeo-slope. We further correlate these systems with analogous hydrocarbon-bearing sequences throughout a large region of the south-east African continental shelf. Using conservative assumptions, we propose that ∼327 Mt CO2 could potentially be stored in two laterally extensive shelf sand sequences, with a further potential for ∼464 Mt CO2 storage in basin floor fan systems in the distal basin.
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