Analysis
INEOS's September 18 Greensand opening announcement expects up to 400,000 tonnes of CO₂ storage annually in its first commercial phase. That is a planning reference, not measured annual injection. The depleted Nini West reservoir lies about 1,800 metres beneath the seabed; this description is not a measured well depth. The following independent calculations do not estimate Greensand's performance.
For an assumed 400,000 tonnes over 8,760 hours, the calendar-average mass rate is 45.6621 tonnes/hour. At assumed effective operating availability of 70%, 80% and 90%, required aggregate mean rates during operating hours become 65.2316, 57.0776 and 50.7357 tonnes/hour. The 80% case is 25% above the calendar average. Availability represents the shared chain's effective operating hours, without adding separate outage allowances. These are neither per-well rates nor demonstrated injectivity or capacity guarantees.
A separate hypothetical annual fixed cost of USD 10 million divided by assumed delivered volumes of 400,000 or 350,000 tonnes gives USD 25 or 28.5714 per tonne. This illustrates fixed-cost dilution only, excluding variable costs and capital recovery. It is not an INEOS cost, tariff, total storage cost or project valuation.
Accounting must reconcile received mass minus stock increases, exports and losses with injection, using meters and stated uncertainty. Stored CO₂ is not automatically verified net emissions reduction: lifecycle boundaries matter. Reservoir pressure, injectivity and fracture constraints remain unknown here; this arithmetic supplies no operating recommendation or actual forecast.