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Downloads/Allshaleoverviewfinal.Pdf, Pp Stratigraphic characterisation of the Collingham Formation in the context of shale gas from a borehole (SFT 2) near Jansenville, Eastern Cape, South Africa By Dawn Ebony Black Submitted in fulfilment of the requirements for the degree of Magister Scientiae in the Faculty of Science of the Nelson Mandela Metropolitan University, Port Elizabeth Supervisor: Prof P.W.K. Booth (Geosciences - Nelson Mandela Metropolitan University) Co-supervisor: Professor M. de Wit (AEON – African Earth Observatory Network/ Nelson Mandela Metropolitan University) Declaration of own work: I, Dawn Black, student number 199217157, hereby declare that this MSc dissertation “Stratigraphic characterisation of the Collingham Formation in the context of shale gas from a borehole (SFT 2) near Jansenville, Eastern Cape, South Africa” is my own work. This dissertation has not previously been submitted for assessment or completion of any other postgraduate qualification at any other university. Sign and date ………………………………………………………………………….. i Acknowledgments I would like to express a special appreciation and thanks to my mentor and supervisor Professor P.W.K. Booth. Your patience, guidance and kindness truly knew no bounds. I would like to thank Professor M. de Wit for allowing me to realise this MSc. The support, encouragement and financial aid that you provide your students is phenomenal; you were truly instrumental in the completion of this dissertation. Thanks to all in the geology department at the Nelson Mandela Metropolitan University, a special thanks to Callum Anderson for your guidance through the world of geochemistry. I would like to thank Inkaba yeAfrika and the Africa Earth Observatory Network for the financial assistance. I would like to thank the British Geological Survey for carrying out all the mercury porosimetry measurements; the Applied Petroleum Technology AS for all T.O.C. measurements; the Council for Geoscience for all XRF and XRD analyses and the time allowed to work on the dissertation; Professor Mike Lee in the Department of Physics and Centre for HRTEM for allowing me to use SEM; and the NMMU Geology Department for the preparation of thin sections and the use of an optical microscope. I would like to thank my parents, Errol Black (“BSc.hons.assis”) and Carol Black for the unending support, unfailing love and interest they show in all my endeavours. Like everything in life, I could not have done this without you. I am excited and relieved that we have reached the end of our MSc journey and I am so excited to see what the future holds for us. Thank you to my beloved husband and favourite dive buddy Robert (Robsy) Francis for all your patience and encouragement, you were ‘rock’ steady when I needed it most. The world is our oyster. Miss Pee and Miss Claire, your support was unending and your strict scoldings and encouragements helped me achieve my goal. To my colleague and friend Debbie, you saw me through the highs and lows of this MSc with positivity and a huge amount of patience. Special thanks to Marilyn, you are such a dear and your motivational skills are extraordinary. Thank you Taufeeq, your kindness and willingness to help at any hour is so appreciated. Thank you to my special friends Gideon Brunsdon and Jean-Luc Mondon, the support you have given me through the completion of this dissertation has been truly amazing and I am so appreciative. Pietie and Jesse, your patience was at times tried – but you managed to begrudgingly wait to play. You are mammas favourite little beloveds’. Budgie your sweet songs lifted my spirits many an evening and weekend. ii Abstract This study is an extensive lithological, petrographical, mineralogical and geochemical description of fresh Collingham Formation core samples collected from borehole SFT 2, located on the farm Slangfontein, south of Jansenville in the Eastern Cape, South Africa. The borehole, drilled to 295 m on the northerly limb of a shallow westerly plunging syncline, intersected the lower Ecca Group rocks of the Ripon, Collingham, Whitehill and Prince Albert Formations and terminated in the upper Dwyka Group. A comprehensive log and stratigraphic column were compiled for the Collingham Formation and fresh core samples were analysed using X-Ray Diffraction (“XRD”), X-Ray Fluorescence (“XRF”), mercury porosimetry, and Total Organic Carbon (“TOC”). Thin section microscopy and Scanning Electron Microscopy (“SEM”) analyses were carried out on selected samples of core from borehole SFT 2. The matrix supported, massive to laminated lithological units of the Collingham Formation are interpreted as detrital, terrigenous sediments. These sediments are composed of intercalated fine-grained, poorly sorted, non-fissile mudstone; fine- to very fine-grained, predominantly pyroclastic airfall tephra; and less common fine-grained sandstones. Sediments of the Collingham Formation are considered to be immature, composed primarily of clay and aluminosilicates. The predominance of a clay fraction and aluminosilicates in mudstone samples is indicated by elevated K 2O/Al 2O3 ratio values, and the relationship of Zr, Al 2O3 and TiO 2. The presence of glauconite within the Collingham Formation indicates deposition in a mildly alkaline, slightly reducing marine environment. Rb/K ratio values (1.9 – 2.3 x 10 -3) indicate brackish to slightly marine conditions, while low Zr/Rb ratio values indicate a low hydro-energy environment, with stable bottom water conditions. Hf and Nb concentrations indicate that detrital input was greatest during the deposition of tuffaceous units; while stable mineral assemblages and a low Fe 2O3/K 2O ratio values indicate deposition close to the source. A variation in Si/Ca values indicate times when sediments were affected by turbidity, interspersed with times of relative quiescence. The predominance of K 2O over Na 2O indicates that the Collingham Formation is alkali-rich, while SiO 2/Al 2O3 ratio values and the relationship of Zr, Al 2O3 and TiO 2 indicate that sediments are immature. In the lower portion of the formation, non-sulphidic, anoxic conditions are indicated by Mn/Al, V/(V+Ni), V/Cr ratio values, the Fe-Mn- V content, and the correlation between V and TOC. The upper portion of the formation is considered dysoxic, due to the presence and distribution of pyrite framboids, which indicate a fluctuating O 2 level, likely indicating deposition at the interface between anoxic and slightly more oxic conditions. V/Cr ratio values indicate that the O 2 regime was lowest during the deposition of the mudstones. The Chemical Index of Alteration (“CIA”) indicates a consistent weathering regime throughout the deposition of the Collingham Formation, associated with a temperate climate on the interface between glacial and tropical conditions. Although an anoxic and low hydro-energy environment is generally favourable for hydrocarbon accumulation, the Collingham Formation contains low levels of Total Organic Carbon (well below 0.9 %) and low porosities (ranging from 0.35 % to a maximum of 2.22 %), both of which are characteristic of a poor source for gas accumulation. Due to the laminate nature, permeability and fracturability of the Collingham Formation, there is the potential that the formation may form a good sealing sequence to the potentially gas-rich Whitehill Formation below. The metamorphic impact related to the Cape Orogeny ( ± 250 Ma), and reflected in the textures of the minerals making up the sediments of the Collingham Formation, suggests the enhancement in the sealing efficiency of this formation. iii Table of contents Chapter 1- Introduction ......................................................................................... 1 1.1.1 Project Aims and Objectives ....................................................................... 1 1.1.2 Project Outline ............................................................................................ 2 1.1.3 Shale gas ...................................................................................................... 3 1.1.4 Natural gas reservoirs and extraction ......................................................... 4 1.1.5 The history of natural gas ............................................................................ 8 1.1.6 Shale gas as an unconventional energy source .......................................... 8 1.1.7 Shale gas in South Africa: the potential Karoo shale gas play .................. 12 1.1.8 Potential threats related to shale gas exploitation ................................... 14 Chapter 2- Geological Setting of the Karoo Basin ................................................. 16 2.1 Geodynamic Setting of the Karoo Basin ......................................................... 16 2.1.1 Karoo Basin Development (retro-arc foreland basin) ............................... 21 2.1.2 Karoo Basin Development (early continental extension) ......................... 26 2.2 Karoo Supergroup ........................................................................................... 31 2.2.1 Lithostratigraphy of the lower Ecca Group in the Eastern Cape, South Africa ................................................................................................................... 36 Chapter 3- Material and Methods ........................................................................ 50 3.1 Borehole SFT 2 ................................................................................................. 50 3.1.1 Locality of Borehole SFT 2 ........................................................................
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