Carbon capture and storage is one of the technologies that could help reduce CO2 concentration in the atmosphere while contributing to cutback of Greenhouse Gas emissions. Depleted oil and gas fields are favorable targets for CO2 storage because existing wells can be readily used as injection wells. However, a number of abandoned wells also serve as gateway to the reservoir which should be considered in the context of effective Carbon capture and storage. Wellbore cement is a very essential element in wellbore systems that serve as a barrier between different zones in the subsurface. The fractures inside wellbore cement sheath, one of the possible pathways for CO2 leakage to surface and/or fresh water aquifers, impair the effective sealing of the wellbore cement. Hence, the existence of microfractures poses a risk for Carbon capture and storage.
The purpose of this experimental study is to gain understanding about the effect of acidic brine on the behavior of cement fracture and porosity. Two experiments were conducted, one under atmospheric and one under high pressure conditions, using CO2 saturated brine. Fracture widening was observed in CT images of the low pressure experiment and was verified with pressure drop calculations. The low pressure experiment resulted in the reduction of porosity whereas the high pressure experiment resulted in a slight increase in porosity. The porosity reduction was caused by calcite deposition which was confirmed by mineralogical analysis, ESEM images and effluent brine analysis. There were 2 mechanisms working simultaneously: leaching and precipitation (carbonation). It appeared that leaching took place first and drove the carbonation process. Leaching resulted in an increase in porosity whereas carbonation resulted in a reduction of porosity. In a possible leakage scenario, acidic brine exposure may result in a reduced fracture aperture due to carbonation coupled with confining stress around cement sheath.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-11172010-123224 |
| Date | 17 November 2010 |
| Creators | Yalcinkaya, Tevfik |
| Contributors | Sears, Stephen O., Hughes, Richard G., Radonjic, Mileva |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-11172010-123224/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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