Negatively buoyant CO ₂ solution sequestration in synformal traps

Abstract

Dissolving CO2 into water or brine produces a denser fluid than the CO2-free equivalent at all salinity, temperature and pressure conditions relevant to sedimentary basins. Negative buoyancy of CO2 solutions opens the possibility of utilizing negative relief trapping configurations for CO2 sequestration, as opposed to structural highs conventionally sought for positively buoyant fluids such as hydrocarbons or pure CO2. Exploring sedimentary basins for negative buoyancy traps can readily utilize hydrocarbon exploration datasets and techniques. Some major systemic differences when exploring for negative as opposed to positive buoyancy traps are examined here. Trap spatial scale is a consideration due to the inherent long-wavelength synformal geometry of basins. Antiforms are areally restricted relative to synforms, which may be embedded within larger-scale synformal closure at length scales right up to that of the basin itself. Multiscale synformal structure varies with basin type and may not be fully identified due to truncation effects arising from data coverage limitations. Similar to hydrocarbon exploration, CO2 trap exploration must consider potential sequestration volumes in an uncertainty and risk framework. Charge risk is unnecessary in sequestration projects, however, the multiscale nature of synformal traps should be considered when estimating range of storage volumes.This article is part of the Energy Geoscience Series available at https://www.lyellcollection.org/cc/energy-geoscience-series

APPLICATION OF MUD GAS DATA AND LEAKAGE PHENOMENA TO EVALUATE SEAL INTEGRITY OF POTENTIAL CO2STORAGE SITES: A STUDY OF CHALK STRUCTURES IN THE DANISH CENTRAL GRABEN, NORTH SEA

“…Finally, supercritical CO 2 (scCO 2) ) is a relatively dense fluid phase (with a liquid-like density) although the viscosity is gas-like under the existing reservoir pressure and temperature conditions that exceed the respective critical points. In most sedimentary basins, the pressure and temperature requirements for scCO 2 are reached at depths greater than approximately 750-900 m (Stewart, 2022;Stewart and Riddell, 2022). In the current study, a reservoir burial depth of 800 m is assumed; this agrees with Chadwick et al (2009) who also suggested depths greater than 800 m at pressures >8 MPa for optimizing the storage efficiency.…”