CO2 Sequestration [Buoyancy Trapping]

Buoyant trapping remaining the key process for CO2 storage during the injection and early stage of storage, would it remain feasible to capture the following details @ field-scale – following the injection of CO2 into the base of the reservoir?

(a) The horizontal lateral migration of plumes through least resistive pathways in horizontal direction or through the most permeable beds or channels in horizontal direction – until it finds a least resistive pathway in the vertical direction (which may be, either fault or fracture), through which CO2 would start migrating upwards; and would start accumulating below the base of the cap-rock/seal

(b) The space and time dependent – horizontal and vertical aquifer/reservoir heterogeneities – that essentially dictate the horizontal and vertical migration of CO2; and in turn, the resulting CO2-plume behavior.

(c) The areal/volumetric extent and amount of CO2 buoyant trapping, when CO2 is injected into reservoirs in liquid-phase (say, @ 8 MPa); and when CO2 is injected as a super-critical fluid (say, @ 8 MPa & @ 32 deg C) - pertaining to a depth of 1 km.

(d) Structural trapping of CO2 resulting from a fault intersecting a dipping zone of the reservoir; and its associated details on the location of sealing cap-rock and rock-matrix with reference to the fault structure.

(e) The way the rock deformation (brittle or ductile deformation) progresses with time as a function of aquifer/reservoir temperature, lithostatic pressure & rock characteristics (porosity, permeability, rock-mineral composition, mineral distribution, grain-size, grain-size distribution and the presence of interstitial fluids and their chemical composition).

(f) The way CO2 gets trapped in folds either in anticlines or in domes.

(g) The way the pressure gets accumulated near the injection well (along with the details of peak pressure); and the way, the pressure gets spread over and mitigates with time, following a typical structural trapping.

(h) The way CO2-brine interface gets disrupted – as a function of capillary threshold pressure.

(i) The way, the upward migrating CO2 gets halted by the presence of capillary threshold pressure.

(j) The way, the capillary threshold pressure gets enhanced upon reaching the cap-rock/seal from its high-permeable reservoir unit.

(k) The way, the buoyancy pressure keeps evolving as a function of difference in densities between CO2 & brine; and the height of the trapped CO2 column beneath the cap-rock.

(l) The moment, when buoyancy pressure exceeds the capillary threshold pressure (leading to CO2 escape).

Suresh Kumar Govindarajan

Professor (HAG) IIT-Madras

https://home.iitm.ac.in/gskumar/

https://iitm.irins.org/profile/61643