Fractures are mechanical ruptures in rocks, form by stress (lithostatic, tectonic, and thermal stresses and high fluid pressures) concentrations around flaws, heterogeneities, and physical discontinuities at a variety of scales. In groundwater reservoirs, mainly in those formed within relatively less permeable or hard rocks, connected fractures may form privileged conduits for fluid flow and solute through the rock, and therefore needs to be located and quantitatively (geometry, permeability, and ability to transport solute) appreciated for a better understanding of water flow and mass transport processes in the subsurface. Many techniques have been adapted from petroleum applications to address these issues and are reviewed in the present study with after an overview on geological and geo-mechanical features that evolve fracturing.
Very few existing tools are cost-effective and easy to be performed on the field. The FEC (Fluid Electrical Conductivity) based techniques; mainly the single borehole based ones involve often, relatively cost effective equipments and are simple. The present study focus also on the applicability of âFlowing Fluid Electrical conductivity loggingâ (Tsang et al., 1990; Doughty et al., 2005) and the FEC based dilution test (well dilution) for fracture characterization in the Karoo aquifer. The FFEC is found to be a promising technique for local fracture characterization, mainly in contamination studies (investigation and scenario testing), like in mine environments; and is recommended to be experienced in South-Africa, particularly in the meta-sediments of the Karoo environment. The FEC based dilution test (well dilution) is gaining interest in fracture characterization in South Africa (Mohr Samuel and van Biljon Willem., 2009; Lasher Candice et al., 2009) and has been assessed on two experimental fields in the Karoo Aquifer. The technique is found to constitute a powerful tool for detection of flowing fractures and for qualitative interpretation. The Drost et al (1968) analytical solution suggested for the analysis of the test data (Cook et al., 2001a; Love et al., 2002) have been applied and yielded semi-quantitative values that can be used as first estimation of the groundwater velocity from flowing points into the studied boreholes. However, due to non ideal condition, refinements are still needed mainly for the field procedure and for the consideration of the mass circulation that may be associated with density gradient along the borehole.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-05272013-104519 |
| Date | 27 May 2013 |
| Creators | Pacome, Ahokpossi Dehouegnon |
| Contributors | Dr SR Rainier Dennis |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-05272013-104519/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto 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 University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, 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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