Impacts of injection pressure of a dip‐angle sloping strata reservoir with low porosity and permeability on CO 2 injection amount

Sloping strata reservoirs with low porosity and permeability are widely distributed in China. The first CO 2 capture and geological storage (CCS) demonstration project in China that has been constructed in the Ordos Basin is a representative. In this paper, a 3D numerical model was constructed to evaluate the influence of injection pressure and strata dip angle on the CO 2 injection amount in a sloping strata reservoir during CO 2 injection period. We reached the following conclusions: (i) There is a ‘balance time point (BTP)’ for the total CO 2 injection amount between a horizontal reservoir and a sloping one, and the BTP will decrease with the injection pressure increase. (ii) The influence of the dip angle of a sloping reservoir on the total injection amount is non‐monotonicity. For a fixed injection pressure, before the BTP, the greater the dip angle, the greater the CO 2 injection amount, but after the BTP, the change rule is reversed. (iii) The injection pressure significantly affected the total injected CO 2 amount, but the influence of the dip angle (in the range of 0° to 15°) on the total injection amount was not significant during injection. (iv) To a sloping reservoir, for long time injection (i.e., injection time is longer than the BTP), the bigger the dip angle, the greater the distance of the CO 2 upward migration, and the smaller the total injected amount compared to the horizontal reservoir. So, in actual site selection of a CCS project, the small dip angle reservoir was beneficial. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.