Aquifer management for CO₂ sequestration /
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| Format: | Thesis eBook |
| Language: | English |
| Published: |
[College Station, Tex.] :
[Texas A&M University],
[2010]
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| Subjects: | |
| Online Access: | Link to OAK Trust copy |
| Abstract: | 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. |
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| Item Description: | "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created 2010-08-20 08:31:34). Electronic resource. |
| Physical Description: | 1 online resource. |
| Bibliography: | Includes bibliographical references. |