Storage of carbon dioxide is being actively considered for the reduction of green
house gases. To make an impact on the environment CO2 should be put away on the
scale of gigatonnes per annum. The storage capacity of deep saline aquifers is
estimated to be as high as 1,000 gigatonnes of CO2.(IPCC). Published reports on the
potential for sequestration fail to address the necessity of storing CO2 in a closed
system. This work addresses issues related to sequestration of CO2 in closed aquifers
and the risk associated with aquifer pressurization. Through analytical modeling we
show that the required volume for storage and the number of injection wells required
are more than what has been envisioned, which renders geologic sequestration of CO2
a profoundly nonfeasible option for the management of CO2 emissions unless brine is
produced to create voidage and pressure relief. The results from our analytical model
match well with a numerical reservoir simulator including the multiphase physics of
CO2 sequestration.
Rising aquifer pressurization threatens the seal integrity and poses a risk of CO2
leakage. Hence, monitoring the long-term integrity of CO2 storage reservoirs will be a
critical aspect for making geologic sequestration a safe, effective and acceptable
method for greenhouse gas control. Verification of long-term CO2 residence in receptor formations and quantification of possible CO2 leaks are required for
developing a risk assessment framework. Important aspects of pressure falloff tests for
CO2 storage reservoirs are discussed with a focus on reservoir pressure monitoring
and leakage detection. The importance of taking regular pressure falloffs for a
commercial sequestration project and how this can help in diagnosing an aquifer leak
will be discussed.
The primary driver for leakage in bulk phase injection is the buoyancy of CO2 under
typical deep reservoir conditions. Free-phase CO2 below the top seal is prone to leak
if a breach happens in the top seal. Consequently, another objective of this research is
to propose a way to engineer the CO2 injection system in order to accelerate CO2
dissolution and trapping. The engineered system eliminates the buoyancy-driven
accumulation of free gas and avoids aquifer pressurization by producing brine out of
the system. Simulations for 30 years of CO2 injection followed by 1,000 years of
natural gradient show how CO2 can be securely and safely stored in a relatively
smaller closed aquifer volume and with a greater storage potential. The engineered
system increases CO2 dissolution and capillary trapping over what occurs under the
bulk phase injection of CO2.
This thesis revolves around identification, monitoring and mitigation of the risks
associated with geological CO2 sequestration.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-12-7300 |
| Date | 2009 December 1900 |
| Creators | Anchliya, Abhishek |
| Contributors | Ehlig-Economides, Christine |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | application/pdf |
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