Date of Award

Spring 2021

Document Type

Open Access Dissertation

Department

Earth and Ocean Sciences

First Advisor

Venkataraman Lakshmi

Second Advisor

Michael Bizimis

Abstract

Over the past few decades, measured levels of atmospheric carbon dioxide have substantially increased. One way to limit the adverse impacts of increased carbon dioxide concentrations is to capture and store it inside Earth's subsurface, a process known as CO2 sequestration. This method's success is critically dependent on the ability to confine injected CO2 for up to thousands of years. Establishing effective maintenance of sealing systems of reservoirs is of importance to prevent CO2 leakage. Understanding the nature and rate of potential CO2 leakage related to this injection process is essential to evaluating seal effectiveness and ultimately mitigating global warming.

This study evaluated the impact of familiar chemical reactions between CO2 and in situ subsurface materials and the relationship between CO2 plume distribution and the CO2 leakage within the seal zone. Using subsurface seismic data and well log information, a three-dimensional model consisting of a reservoir and seal zones were created and evaluated for the South Georgia Rift (SGR) basin in the southeastern U.S. The Computer Modeling Group (CMG) package software (GEM 2017) was used to model the effect of CO2 mineralization on the optimal values of fault permeability. The model simulated the chemical reactions between carbon dioxide and mafic minerals to produce stable carbonate rock minerals that form in the fault. Preliminary results show that CO2 migration can be controlled effectively for fault permeability values between 0.1-1 m D. Within this range, mineralization effectively reduced CO2 leakage within the seal zone.

Sequestration of carbon dioxide is an essential method to address carbon dioxide emissions resulting from anthropogenic activities. When this method is implemented, a potential location for CO2 injection must meet the storage capacity demand for commercial CO2 sequestration. This is because the large-scale injection can result in leakage, which undermines the efforts to combat global warming. Tensile failure and mineralization are among many expected issues that need to be studied for such large-scale storage. This study evaluated the relationship between the tensile failure of a reservoir seal and mineralization to maintain sufficient CO2 storage. CO2 injection in a reservoir at high rates rapidly increases pore pressure around the injection well. If this happens under constant total stress, the effective normal stress begins to decrease due to the increased hydraulic injection pressure. When the hydraulic pressure exceeded the effective normal stress, tensile failure occurred. This created various tiny channels. Their resulting conductivity allowed the CO2 plume, particularly the portion in the gas phase, to pass through these channels into the seal's upper part. The tensile failure then temporarily increased the permeability values until mineralization fixed the increase in permeability. The Barton-Bandis fracture permeability model was applied to study the tensile failure in the seal. Through this model, mineralization combined with tension failure caused changes in the porosity network upon CO2 plume migration

Included in

Geology Commons

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