A procedure for determining the preliminary maximum injection pressure for CO2 sequestration


Injection pressure applied in geological Carbon dioxide (CO2) storage must exceed the existing pore pressure in the reservoir rock to sequestrate supercritical CO2 underground. However, high injection pressure generates new fractures or reactivates existing faults in the rock mass, triggering seismic activities. Therefore, the maximum allowable reservoir rock injection pressure must be assessed as an essential parameter to secure CO2 injection before proceeding with geological CO2 storage. The failure criteria for saturated Yutengping Sandstone, which is a reservoir rock at Tiehchenshan, is investigated in this study using consolidated drained triaxial compression tests. The Mohr circles of in-situ stresses under different coefficients of critical fault friction and various depths are then drawn. The maximum allowable reservoir layer injection pressure was obtained through the relationship between the Mohr circles and failure criteria. The failure criterion for peak strength could be used in evaluating the generation of new fractures in intact rocks. The failure criterion for residual strength could be used in assessing the injection pressure causing slip on existing faults. This assessment method is therefore applicable in the preliminary analysis on the suitability and safety of a geological CO2 storage site.

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