School of Earth Sciences - Theses

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Author: Ali, Syed Anas × End date: 2018 × Type: PhD thesis ×

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    Determining the effective surface area of minerals and the implications for near wellbore geochemical reservoir stimulation
    Ali, Syed Anas ( 2018)
    Sufficient CO2 injection capacity is a key criteria for a prospective CO2 storage site and has proven to be a technical impediment for the development of a CO2 storage operation, for example, in case of the ZeroGen project. This study develops and applies geochemical reservoir stimulation procedures involving pH-controlled solutions to promote mineral dissolution and increase permeability of a siliciclastic reservoir to enhance CO2 injectivity. Effective deployment of a geochemical stimulation technique at field scale requires site-specific data and an understanding of the underlying geochemical reactions coupled to fluid flow within a reservoir. Thus, laboratory scale experiments are developed, and experimental results are used in reactive transport simulations using the TOUGHREACT code to assess the degree of mineral dissolution and possible associated increase in porosity and permeability under variable conditions. The surface area of minerals is often one of the least well-constrained variables in porous rocks, and therefore introduces a large uncertainty in reactive-transport modelling results. Weathering reaction rates in natural systems have been shown to be orders of magnitude lower than predicted using models involving assumptions regarding mineral surface area-to-mass ratios. The discrepancy has been explained by several reasons including mineral overgrowth, poor pore-to pore connectivity and heterogeneous flow fields. Therefore, a new methodology has been developed to determine the effective surface area of minerals using core flood experiments and applied to Catherine Sandstone samples. The derived mineral effective surface areas are incorporated into near-wellbore reactive transport models evaluating the feasibility of enhancing permeability through geochemical stimulation.