# Impact of pressure dissipation on fluid injection into layered aquifers

## TL;DR

This paper investigates how lateral and vertical pressure dissipation influence CO2 injection into layered aquifers, revealing that pressure dissipation reduces plume extent and affects storage security.

## Contribution

It introduces a coupled compressible two-phase model that efficiently captures water migration and pressure dissipation effects in layered aquifers during CO2 injection.

## Key findings

- Pressure dissipation suppresses the formation of an advancing CO2 tongue.
- The properties of seals and number of aquifers influence pressure dissipation effects.
- Pressure dissipation impacts the shape and extent of the CO2 plume.

## Abstract

Carbon dioxide (CO2) capture and subsurface storage is one method for reducing anthropogenic CO2 emissions to mitigate climate change. It is well known that large-scale fluid injection into the subsurface leads to a buildup in pressure that gradually spreads and dissipates through lateral and vertical migration of water. This dissipation can have an important feedback on the shape of the CO2 plume during injection, and the impact of vertical pressure dissipation, in particular, remains poorly understood. Here, we investigate the impact of lateral and vertical pressure dissipation on the injection of CO2 into a layered aquifer system. We develop a compressible, two-phase model that couples pressure dissipation to the propagation of a CO2 gravity current. We show that our vertically integrated, sharp-interface model is capable of efficiently and accurately capturing water migration in a layered aquifer system with an arbitrary number of aquifers. We identify two limiting cases --- `no leakage' and `strong leakage' --- in which we derive analytical expressions for the water pressure field for the corresponding single-phase injection problem. We demonstrate that pressure dissipation acts to suppress the formation of an advancing CO2 tongue during injection, resulting in a plume with a reduced lateral extent. The properties of the seals and the number of aquifers determine the strength of pressure dissipation and subsequent coupling with the CO2 plume. The impact of pressure dissipation on the shape of the CO2 plume is likely to be important for storage efficiency and security.