Abstract:

In order to meet the need of evaluatoin of CO₂ geo-sequestration in deep aquifer, CO₂ sequestration mechanisms and capacity evaluation in deep aquifer is proposed. The CO₂ sequestration mechanism includes four main ways: (a)hydrodynamic trapping means a CO₂ migration upwards to the barrier layer and gathered in geologic masses, forming a CO₂ gas phase sequestration; (b)residual gas trapping results from relative permeability hysteresis; (c)solubility trapping means CO₂ dissolves in the formation water and (d)mineral trapping is CO₂ sequestration through geochemical reactions with the aquifer fluids and rocks. Mechanisms for sequestration of CO₂ operate on different time scales and have different degrees of permanency. The ultimate CO₂ sequestration capacity in an aquifer can be defined as the total amount of CO₂ that can trap in solubility and residual gas. On the base of mechanism analysis, the formula on sequestration capacity can be deduced to evaluate sequestration capacity. Sequestration evaluation for a target site can be made based on mechanism and capacity formula.

Key words: greenhouse emission reduction, deep aquifer, CO₂ sequestration, sequestration mechanism, sequestration capacity