FEASIBILITY OF CO₂ SEQUESTRATION IN ABANDONED COAL MINES IN BELGIUM

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Abstract

The concept of storing gas in abandoned coal mines is proven technology (Anderlues, Péronnes). However, this was done for seasonal storage of natural gas in underpressured reservoirs, whereas CO₂ sequestration preferably requires overpressured reservoir conditions for long-term storage. Marl and chalk apparently form a sufficiently tight seal in a number of coal mines, but this will need verification. Safety risks involved with the storage of CO₂ in mines are low. Natural faults and induced fractures need detailed evaluation, especially with respect to changes in the stress-regime. Standard techniques to inject CO₂into reservoirs involve the injection of liquid CO₂. Excessive cooling of the reservoir and injection equipment can be avoided by depressurising CO₂ and injecting it as a gas or, when the reservoir becomes partly fluid-filled, to apply custom-designed injection schemes for injection of liquid CO₂. When CO₂ is injected into a coal mine, it may be stored in free space, in solution in the formation water, or adsorbed in coal. These amounts can be calculated, but not all parameters are sufficiently known to produce reliable results. Therefore, the amounts are split into an ascertained capacity that can be calculated with a known accuracy, and an additional capacity, which is an estimated surplus that cannot be calculated accurately. CO₂ sequestration in coal mines seems to be technically feasible and may be a useful option for Belgium to reduce the industrial emission of greenhouse gases into the atmosphere. A case study for the Beringen-Zolder-Houthalen collieries shows that sequestration is a viable option, even for the ascertained capacity alone. At an injection rate of 300 000 tons/y, sequestration can be operational for about 25 years. This is a conservative estimate, and it may prove possible to inject at 500 000 tons/y for 25 years. This could be a considerable contribution, approximately 3 to 6% of the mitigation required to reach the Kyoto target for Belgium. Petrochemical plants that produce nearly pure CO₂ streams are prime candidates for early opportunity projects in abandoned coal mines.

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A propos de : Kris PIESSENS

A propos de : Michiel DUSAR