Geological storage of CO2: Heterogeneity impact on the behavior of pressure

Abstract

The goal of this study is to investigate and control the pressure buildup during CO2 injection into underground aquifers. Herein, we study how heterogeneity variation over 160 geological realizations influences the pressure behavior of a typical CO2 injection operation. Five geological feature variables are considered as inputs for the sensitivity analysis. These features include various degrees of faults, lobosity, flow barriers, aggradation angle, and progradation direction.Two injection scenarios are examined. In the first scenario, CO2 is injected through a single well at a constant rate and the pressure in the well and the domain is allowed to build up without limit. In the second scenario, a pressure constraint is set on the well and the target injection rate is reduced to keep the pressure below the safety limit. Model responses related to pressure buildup and propagation within the system is studied. We conclude by ranking aggradation angle, progradation direction, and faults as the most influential geological parameters. Injection with the fixed rate into some of the studied geological realizations, mostly with low aggradation angle, results in extreme well and aquifer pressures. This limitation may be avoided by reducing the geological uncertainty for site selection operation or lowering the injection rate.The demonstrated workflow is generic and can be used in any extensive pressure study. The relative ranking of which parameters are the most important may, of course, change if one selects a different injection scenario, injection location, number of injector, or set of geological realizations.