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Characterisation of the Deep Aquifers of South Africa – the Karoo Supergroup and Table Mountain Group

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Characterisation of the Deep Aquifers of South Africa – the Karoo Supergroup and Table Mountain Group CHARACTERISATION OF THE DEEP AQUIFERS OF SOUTH AFRICA – THE KAROO SUPERGROUP AND TABLE MOUNTAIN GROUP NWABISA MAKIWANE Submitted in fulfilment of the requirements for the degree Magister Scientiae in Geohydrology in the Faculty of Natural and Agricultural Sciences (Institute for Groundwater Studies) at the University of the Free State Supervisor: FD Fourie Co-supervisor: A Allwright June 2019 DECLARATION I, NWABISA MAKIWANE, hereby declare that the dissertation submitted by me to the Institute for Groundwater Studies in the Faculty of Natural and Agricultural Sciences at the University of the Free State in fulfilment of the degree of Magister Scientiae, is my own independent work. It has not previously been submitted by me to any other institution of higher education. In addition, I declare that all sources cited have been acknowledged by means of a list of references. I furthermore cede copyright of the dissertation and its contents in favour of the University of the Free State. Nwabisa Makiwane June 2019 - ii - ACKNOWLEDGEMENTS I would hereby like to express my sincere gratitude to all who have motivated and helped me in the completion of this dissertation: God for the strength bestowed upon me throughout this project. My mother (also mentor, best friend and motivator) for the amazing support and encouragement. Thank you for all the sacrifices you have made for me to be where I am today. My supervisor, Dr Francois Fourie, and co-supervisor, Ms Amy Allwright, who motivated and helped me in the completion of this dissertation. Your support, encouragement and valuable advice in this study was appreciated. The Water Research Commission for funding the research project and for the opportunity to be a part of it. A special thanks to Sinethemba Nyalukana for being such a wonderful partner. Thank you for your love and support. The laughter and memories we shared will always be treasured. My dear sister Ayanda Makiwane, thank you for the constant inspiration, prayers and guidance. My sincere gratitude to my friends and colleagues for all their support and love (Vuyi Tumana, Masego Luncwane, Palesa Myeko and Bonelwa Mabovu). And lastly thank you to Chané Swarts for your assistance, it is highly appreciated. - iii - TABLE OF CONTENTS LIST OF FIGURES VIII LIST OF TABLES XI CHAPTER 1 : INTRODUCTION 1 1.1 BACKGROUND 1 1.2 AIMS AND OBJECTIVES 2 1.3 RESEARCH METHODOLOGY 2 1.4 STRUCTURE OF DISSERTATION 3 CHAPTER 2 : LITERATURE REVIEW 5 2.1 INTRODUCTION 5 2.2 DEFINING DEEP 5 2.2.1 Various definitions of “deep” aquifers 5 2.2.2 The various perspectives on deep groundwater according to related disciplines 7 2.2.2.1 Geothermal industry 7 2.2.2.2 Carbon capture and storage industry 7 2.2.2.3 Petroleum industry 7 2.2.3 Revision of the term “deep” with technological advancements 8 2.2.4 Depth-independent definitions of “deep groundwater” 10 2.2.5 Definition of “deep groundwater” for South African aquifers 10 2.2.5.1 Depth to current groundwater exploitation 10 2.2.5.2 Groundwater quality (chemical determinands) 11 2.2.5.3 Unconfined vs confined 12 2.2.5.4 Deep groundwater as groundwater below alluvial/weathered aquifers 13 2.2.5.5 Unexplored depths 13 2.3 DEEP GROUNDWATER QUALITY AND CIRCULATION DEPTHS 13 2.4 DEEP GROUNDWATER DATA 14 2.5 GEOPHYSICAL METHODS FOR DEEP AQUIFER DELINEATION 14 2.6 HISTORICAL EVIDENCE FOR DEEP AQUIFERS IN SOUTH AFRICA 16 2.7 INTERNATIONAL CASE STUDIES ON DEEP AQUIFERS 18 2.7.1 Introduction 18 2.7.2 The deep aquifer system of the Monterey County 18 2.7.3 The deep geohydrology of the Salinas Valley 19 2.7.3.1 Investigation approach 21 2.7.3.2 Hydrostratigraphy of the DMW1 site 21 2.8 NATIONAL CASE STUDIES ON DEEP AQUIFERS 24 - iv - 2.8.1 Introduction 24 2.8.2 The Deep Artesian Groundwater Exploration for Oudtshoorn Supply (DAGEOS) project 25 2.8.2.1 Local Geology and Hydrogeology 25 2.8.3 The Blikhuis Experimental Deep Drilling (BEDD) project 28 2.8.4 Deep carbon storage in South Africa 30 2.8.4.1 Carbon storage in South Africa 32 2.8.5 The Agulhas-Karoo geophysical transect 33 CHAPTER 3 : POTENTIAL DEEP AQUIFERS IN THE KAROO SUPERGROUP AND TABLE MOUNTAIN GROUP 38 3.1 INTRODUCTION 38 3.2 THE KAROO SUPERGROUP 39 3.2.1 Location and extent 40 3.2.2 Geology 40 3.2.3 Geohydrology 46 3.2.4 Karoo dolerites and their relation to deep aquifer systems 46 3.3 THE TABLE MOUNTAIN GROUP 48 3.3.1 Location and extent 48 3.3.2 Geology 49 3.3.3 Geomorphology of the TMG 52 3.3.4 Geohydrology 52 3.4 POTENTIAL DEEP AQUIFERS 54 3.4.1 Potential deep aquifers in the TMG 54 3.4.2 Potential deep aquifers in the Main Karoo Basin 55 3.4.3 Thermal springs as indicators of deep groundwater flow 56 3.4.3.1 Thermal springs of volcanic origin 56 3.4.3.2 Thermal springs of meteoric origin 56 3.4.3.3 Distribution of thermal springs in South Africa 57 CHAPTER 4 : DATA SOURCES FOR DEEP AQUIFERS IN SOUTH AFRICA 59 4.1 INTRODUCTION 59 4.1.1 Boreholes in the National Groundwater Archive 59 4.1.2 The SOEKOR boreholes 61 4.1.3 Boreholes in the database of the IHFC and Pangaea 64 4.1.4 Boreholes in the database of the Council for Geoscience (CGS) 67 4.1.5 The KARIN boreholes 68 4.1.6 Boreholes in the database of the Petroleum Agency of South Africa 69 - v - 4.1.7 Thermal springs 73 4.1.8 Deep mining 74 4.1.8.1 Exploration drilling 74 4.1.8.2 Borehole logs 75 4.1.8.3 Ground and airborne geophysics 75 4.1.8.4 Deep opencast mining 76 4.1.8.5 Underground coal mining 76 4.1.8.6 Mine dewatering 76 CHAPTER 5 : CHARACTERISATION OF THE DEEP AQUIFERS OF THE KAROO SUPERGROUP AND TABLE MOUNTAIN GROUP 78 5.1 INTRODUCTION 78 5.2 THE KAROO SUPERGROUP CHARACTERISATION 79 5.2.1 Introduction 79 5.2.2 Description of the Karoo Supergroup deep aquifer systems 81 5.3 THE CHARACTERISATION OF DEEP AQUIFERS IN THE TABLE MOUNTAIN GROUP 86 5.3.1 Introduction 86 5.3.1 Characteristics of the deep TMG aquifers 88 5.4 CHARACTERISTICS OF DEEP AQUIFERS DERIVED FROM THERMAL SPRINGS 90 5.4.1 Location and type 90 5.4.2 Chemical indictors of deep groundwater 92 5.4.3 Circulation depths of deep groundwater 93 5.4.4 Characteristics of water from thermal springs 93 CHAPTER 6 : ACTIVITIES THAT MAY HAVE AN IMPACT ON DEEP AQUIFERS 95 6.1 INTRODUCTION 95 6.2 DEEP MINING 96 6.2.1 Potential impacts of mining on deep-aquifer systems 98 6.2.2 Impacts on groundwater quality 98 6.3 DEEP OIL AND GAS PRODUCTION 99 6.3.1 Potential impacts of conventional oil and gas production on deep aquifer systems 99 6.3.1.1 Approaches to Protect Deep Aquifers 100 6.4 UNCONVENTIONAL OIL AND GAS PRODUCTION 101 6.4.1 Coalbed methane 101 6.4.1.1 Potential impacts of coalbed methane extraction on deep aquifers 102 6.4.2 Shale gas 102 6.4.2.1 Potential impacts of shale gas extraction on deep aquifer systems 103 - vi - CHAPTER 7 : CONCLUSIONS AND RECOMMENDATIONS 104 7.1 CONCLUSIONS 104 7.2 RECOMMENDATIONS 109 REFERENCES 111 - vii - LIST OF FIGURES Figure 2. 1 A relative representation of the depth of oil wells in feet ............................................ 9 Figure 2. 2 Location of deep aquifer system monitoring-well site in the Salinas Valley at Marina, California (US Geological Survey, 2002) .................................................... 20 Figure 2. 3 Location of deep aquifer system monitoring-well site and selected water-supply wells, Marina, California (US Geological Survey, 2002) ......................................... 22 Figure 2. 4 Lithology and geophysical logs for the deep aquifer system monitoring-well site, Marina, California ...................................................................................................... 23 Figure 2. 5 Locality map for the DAGEOS project (Umvoto, 2005) ........................................... 26 Figure 2. 6 Preliminary geological cross-section through the BEDD project study area (Hartnady & Hay, 2002a) ........................................................................................... 29 Figure 2. 7 Schematic showing the different regions of influence related to CO2 storage (Birkholzer et al., 2009) ............................................................................................... 31 Figure 2. 8 Vertical profiles of pressure, salt mass fraction, temperature and saline density from top of aquifer to storage formation (Birkholzer et al., 2009) ......................... 31 Figure 2. 9 Total field free-air aeromagnetic map showing the western and eastern lines of the Agulhas-Karoo Geophysical Transect (AKGT), the Beattie Magnetic Anomaly (BMA) and the 100 km section used for this study (Lindeque et al., 2011) ........... 35 Figure 2. 10 New crustal tectonic model derived from the integration of seismic reflection data, wide-angle refraction data, magnetotelluric measurements, aeromagnetic data, receiver function analyses and existing boreholes as discussed in the text (Lindeque et al., 2011) ................................................................................................. 36 Figure 2. 11 Comparing models of the Cape and Karoo Basins in the upper crust (< 15 km). (a) Hälbich et al. (1993) model, (b) Chevallier et al. (2004) model, (c) Johnson et al. (2006) model, and (d) current model (Lindeque et al., 2011) .................................. 37 Figure 3. 1 Location of the Karoo basins in South Africa, with the location of a cross-section line through the basin (Viljoen et al., 2010) .............................................................. 40 Figure 3. 2 Schematic areal distribution of the lithostratigraphic units of the Karoo Supergroup and location of sections A-E and 1-3 (Johnson et al., 2006) ............... 43 - viii - Figure 3.
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