Potential Benefits of Horizontal Wells for CO[sub.2] Injection to Enhance Storage Security and Reduce Leakage Risks

This work suggests that horizontal injectors are a safe way to keep CO2 trapped in the storage site and reduce/prevent any unexpected event associated with leakage through the caprock since the horizontal well minimizes or avoids CO2 contact with the caprock. This study used numerical simulations of CO[sub.2] storage to identify the benefits of horizontal wells for geological carbon storage, such as enhancing CO[sub.2] trapped in porous media due to relative permeability and capillary hysteresis. Two injection schemes were tested: one using a vertical injector and the other employing a horizontal well. The results revealed two main findings. Firstly, the horizontal injection well effectively prevented or minimized CO[sub.2] penetration into the caprock across various sensitivity scenarios and over a thousand years of CO[sub.2] redistribution. Secondly, horizontal wells provided a safe approach to trapping CO[sub.2], increasing its entrapment as a residual phase by up to 19% within the storage site. This, in turn, reduced or prevented any unexpected events associated with CO[sub.2] leakage through the caprock. Additionally, the paper proposes a practical method for designing the optimal length of a horizontal well. This method considers a combination of two parameters: the additional CO[sub.2] that can be trapped using a horizontal well and the gravity number. In the case of the reservoir model of this study, a horizontal branch with a length of 2000 m was found to be the most effective design in enhancing CO[sub.2] entrapment and reducing CO[sub.2] buoyancy.