Four trapping mechanisms. Thousands of years of security. Proven at Sleipner since 1996.
When CO₂ is injected into a geological formation at depths greater than 800 metres, it enters a supercritical phase — behaving simultaneously like a liquid and a gas — and is lighter than the surrounding saline formation water. Over time, multiple trapping mechanisms work together to progressively immobilise the CO₂ and prevent its return to the surface. This multi-mechanism trapping is why properly selected and characterised geological formations provide secure storage over geological timescales.
The four principal trapping mechanisms are: structural trapping, where CO₂ is trapped beneath a low-permeability cap rock (like a dome or anticline) that prevents upward migration; residual trapping, where CO₂ becomes immobilised in the pore spaces of the rock as capillary forces prevent it from moving; solubility trapping, where CO₂ dissolves into the formation brine and sinks, eventually reaching the bottom of the reservoir; and mineral trapping, where dissolved CO₂ reacts with rock minerals to form stable carbonate solid phases over hundreds to thousands of years.
For onshore India, the geological storage targets are predominantly deep saline aquifers within the major sedimentary basins — formations that have never produced hydrocarbons but that contain porous and permeable sandstone or carbonate rock saturated with saline water at depths of 800–3,000 metres. These formations have not been extensively characterised for CO₂ storage because they have no commercial value for oil and gas exploration — but preliminary analysis of basin-scale geological data suggests storage capacities that vastly exceed India's foreseeable capture volumes.
NCM has conducted preliminary storage potential screening for five onshore sedimentary basins using GSI, ONGC, and published geological data. Each basin is assessed against three criteria: estimated CO₂ storage capacity, quality of geological seal, and proximity to major industrial emission clusters.
Deep saline aquifers are the primary onshore storage target for large-scale Indian CCUS deployment. They are geographically widespread across all of India's major sedimentary basins, have no competing commercial use that creates rights conflicts, and have estimated capacities that dwarf India's foreseeable capture volumes. The challenge with saline aquifers is characterisation — unlike depleted oil and gas reservoirs, saline aquifers have limited exploration borehole data, and significant appraisal investment is required before injection can proceed. NCM is working with the Ministry of Earth Sciences to design a targeted appraisal programme for India's highest-priority saline aquifer formations.
Depleted oil and gas reservoirs are the most immediately developable onshore storage option — because existing production data provides detailed subsurface characterisation, well infrastructure may be reusable for CO₂ injection, and the geological seal has already proved effective by retaining hydrocarbons for millions of years. ONGC's depleted fields in Gujarat (Ankleshwar, Gandhar, Mehsana), Rajasthan (post-EOR Mangala), and Assam (Naharkatiya, Moran) are all candidate storage sites where CO₂-EOR integration makes storage development commercially viable before the dedicated storage framework is in place.
Coal seam storage — injecting CO₂ into deep, unmineable coal seams where it adsorbs onto coal surfaces and displaces methane (Coal Bed Methane + CCS) — is a theoretically attractive option for India given the country's vast coal reserves. However, the low injectivity of Indian coals (high ash content, low permeability) and the predominantly thin seam characteristics of Gondwana coal deposits make coal seam storage significantly more challenging in India than in Australia or the US. NCM's current assessment is that coal seam storage is unlikely to be a major pathway for Indian CCUS in the near term, though niche applications in specific geological settings may be viable.
Estimated Indian saline aquifer CO₂ storage potential — preliminary basin-scale assessment
Estimated depleted reservoir storage capacity across ONGC's onshore field portfolio
Minimum injection depth for supercritical CO₂ — where CO₂ density maximises storage efficiency
Typical maximum economic onshore injection depth — below this, drilling and compression costs escalate
The CO₂CRC Otway Basin project in Victoria, Australia is the world's most comprehensively monitored onshore CO₂ storage research site — providing 15+ years of injection, monitoring, and modelling data that NCM applies directly to Indian onshore storage appraisal methodology. Otway Basin demonstrated that CO₂ can be safely injected and monitored in a depleted gas reservoir at modest depth (approximately 2 km), providing the proof of concept for Australian and international onshore storage development.
The Otway monitoring programme — involving 4D seismic surveys, geochemical sampling of formation water, atmospheric CO₂ monitoring, microseismic monitoring, and wellbore integrity testing — provides the benchmark MVR design that NCM uses for Indian storage permit applications. Regulators and DFI lenders are familiar with the Otway monitoring approach and its verification standards, making Otway-aligned MVR plans significantly more credible in the permitting and financing process than bespoke or theoretically-derived designs.
The CO₂CRC has also developed a storage site selection and ranking methodology — combining geological, engineering, economic, and regulatory criteria into a systematic assessment framework — that NCM is adapting to Indian geological and regulatory conditions for the national CO₂ Storage Atlas. This methodology has been peer-reviewed and published extensively, providing the scientific credibility that India's storage atlas will require to inform government policy decisions and DFI financing.
Whether you are a government body seeking policy advice, an industrial company facing CBAM exposure, or an investor seeking CCUS project opportunities — our team is ready to engage.