CMI Annual Report 2022

Research Highlight
India is the third largest and fastest growing emitter of CO 2
globally. India’s energy mix includes a large fleet of coal-fired
power plants whose operational lifetimes extend decades into
the future. As a result, proposed pathways to net-zero include
carbon capture and storage at a rate of hundreds of millions of
tonnes of CO 2
(MtCO 2
) per year by 2035. This will require large
amounts of accessible storage capacity in subsurface rock
formations. The sedimentary formations usually relied upon
to provide that capacity are severely limited in India, where
the geology is characterized by ancient granitic basement rock
and the Deccan Traps, a large deposit of flood basalt (Figure
4.1a). A growing body of research on rapid carbon
mineralization in basalt formations has suggested that the
Deccan Traps may be able to provide significant storage
capacity for CCS.
To assess whether the Deccan Traps are likely to be able to
accommodate large-scale CCS, the Celia lab, led by graduate
student Tom Postma, (1) mapped the area in three spatial
dimensions; (2) considered necessary constraints on injection
depth; and (3) analyzed the geology of the rock volume
residing at suitable depths to gauge the likelihood of finding
viable injection targets.
In the absence of basin-wide three-dimensional geological
datasets, Postma and Celia combined data from many different
sources to obtain a large, internally consistent dataset that
covers the whole region of interest (Figure 4.1b). After mapping
the surfaces that mark the top and base of the Deccan Traps,
they estimated the total basalt thickness at every location
(Figure 4.1c). The resulting volume of basalt was around
300,000 km 3 , which is consistent with estimates found in the
literature.
Virtually all proposed implementations of CCS involve
injection of separate-phase, supercritical CO 2
, which has a
much higher density than CO 2
in the gas phase. To inject and
store CO 2
as a supercritical fluid, the pressure and temperature
in the target formation must exceed the critical pressure and
temperature for CO 2
: 7.4 MPa and 31.1°C, respectively. In
practice, this imposes a minimum injection depth of around
750 m. Because the top of the Deccan Traps largely coincides
with the ground surface, the depth requirement implies that
the top 750 m of basalt are not suitable for CO 2
storage. Only
28% of the total rock volume found at depths greater than 750
m remains viable. This deeper basalt is found only in limited
areas, imposing significant geographical constraints on
available injection locations (Figure 4.1d).
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Carbon Mitigation Initiative Twenty-second Year Report 2022