Accessing the extent of kerogen/bitumen interactions on source rock maturation and hydrocarbon generation Mohammad Hazwan Azri, BEng, MSc. Thesis submitted to the University of Nottingham for the degree of Doctor of Philosophy December 2013 Department of Chemical and Environmental Engineering University of Nottingham Abstract In order to ascertain whether kerogen and the heavy oil or bitumen generated during the initial stages of source rock maturation then go on to produce similar gas yields compared to the natural situation when they are present in source rocks, a study has been conducted on an immature type II Kimmeridge Clay Formation (KCF) source rock (Dorset, United Kingdom) with different total organic carbon contents (14, 25 and 30 % TOC), and all having an initial vitrinite reflectance (VR) of approx. 0.4 % Ro. Anhydrous and hydrous pyrolysis experiments were conducted on the whole immature source rock, the isolated partially matured bitumen-extracted source rock and the isolated bitumen (bitumen generated and extracted from the initial source rock) and mixtures of the isolated partially matured source rock and bitumen using two types of Hastalloy vessels (22 and 25 ml) at 320-420 °C for 7-48 h over a pressure range of 115- 900 bar. Hydrocarbon gas yields and the increase in VR were greater from the whole rock experiments compared to the experiments on the isolated partially matured source rock and isolated bitumen (no mineral matter present), as well as the experiments on mixtures of the isolated partially matured isolated source rock and bitumen combined. The effect of particle size were also found to be of significance as higher gas yields were obtained from recombined mixture experiments using powdered samples (14 % TOC source rocks) compared to using rock chips (30 % TOC source rocks). Hydrocarbon gas yields, pyrobitumen yields, and VR values were found to decrease as pressure increases towards 500 and 900 bar compared to 180 bar at 350 °C where the effects of pressure retardation were found to be much more significant from the partially matured source rock maturation and bitumen in isolation than from the whole source rock. At 420 °C, gas generation, bitumen plus oil and coke yields were not affected by pressure, but VR decreases going from 310 bar to 500 and 900 bar. The results obtained demonstrate that the interplay of inherent mineral matter, reactant phase, source rock/kerogen, bitumen and pressure are key factors in determining the extent of hydrocarbon generation and source rock maturation in geological basins. I Publication Uguna, C.N., Azri, M.H., Snape, C.E., Meredith, W., and Carr, A.D. (2013) „A hydrous pyrolysis study to ascertain how gas yields and the extent of maturation for a partially matured source rock and bitumen in isolation compared to their whole source rock‟, Journal of Analytical and Applied Pyrolysis, 103, 268-277 II Acknowledgements First and foremost, I would like to express my deepest gratitude to my supervisor Professor Colin Snape for his supervision and guidance during my PhD course and Dr. Clement Uguna for his support and advice throughout my research and writing of this thesis. My appreciation also goes to Dr. Andrew Carr and Dr. Will Meredith for their help on the vitrinite reflectance measurements and contributions towards the paper submitted to the Journal of Analytical and Applied Pyrolysis, and Mr. David Clift for his help on preparing the block samples utilized for the vitrinite reflectance measurements. I would also like to extend my gratitude to all members of the University of Nottingham‟s technical staff who gave me their time and assistance in the laboratory and to all my friends and colleagues who have given their support and shared their knowledge with me. I would also like to thank the Government of His Majesty the Sultan and Yang Di- Pertuan of Brunei Darussalam for their generosity in financially supporting my PhD program and my entire undergraduate and postgraduate studies in the United Kingdom. Last but not the least; I would like to thank my beloved family: my father Azri Nawi, mother Dk. Mariam Hj. Tajudin, my brothers Hadi Hilmi and Hadi Azmi, my youngest sister Khairunnisa and my fiancé Ili Adnan for their unconditional love, encouragement and continuous support. III List of Contents Chapter 1: Introduction and scope of study .................................................................. 1 Chapter 2: Literature review .......................................................................................... 3 2.1. Kerogen. .................................................................................................................. 3 2.1.1. Type I kerogen. ................................................................................................ 3 2.1.2. Type II kerogen. ............................................................................................... 4 2.1.3. Type III kerogen. .............................................................................................. 5 2.1.4. Type IV kerogen. ............................................................................................. 5 2.2. Organic matter maturation. ..................................................................................... 6 2.2.1. Diagenesis. ....................................................................................................... 6 2.2.2. Catagenesis. ...................................................................................................... 6 2.2.3. Metagenesis. ..................................................................................................... 7 2.3. Reaction path of kerogen during hydrocarbon generation. ..................................... 8 2.4. Constituents in petroleum. .................................................................................... 10 2.4.1. Bitumen. ......................................................................................................... 12 2.4.2. Pyrobitumen. .................................................................................................. 13 2.5. Petroleum alterations in geological basins. ........................................................... 14 2.6. Maturity indicators for source rocks. .................................................................... 16 2.7. Biological markers. ............................................................................................... 18 2.7.1. Acyclic Isoprenoids. ....................................................................................... 19 2.7.2. Hopanes. ......................................................................................................... 20 2.7.3. Steranes. ......................................................................................................... 21 2.8. Pyrolysis. ............................................................................................................... 23 2.8.1. Anhydrous pyrolysis. ..................................................................................... 24 2.8.2. Hydrous pyrolysis. ......................................................................................... 25 2.8.3. High pressure pyrolysis. ................................................................................. 26 2.9. The effects of water on hydrocarbon generation and source rock maturation. ..... 27 2.10. The effects of pressure on hydrocarbon generation and source rock maturation. ...................................................................................................................................... 30 2.11. The effects of minerals on hydrocarbon generation and source rock maturation. ...................................................................................................................................... 35 Chapter 3: Experimental techniques and methodology. ............................................ 38 3.1. Experimental techniques. ...................................................................................... 38 IV 3.1.1. Gas chromatography. ..................................................................................... 38 3.1.2. Gas chromatography-mass spectrometry. ...................................................... 40 3.2. Methodology. ........................................................................................................ 42 3.2.1. Sample description. ........................................................................................ 42 3.2.2. Pyrolysis equipment and experimental procedures. ....................................... 42 3.2.3. Pyrolysis configurations and experiments. .................................................... 47 3.2.3.1. Bitumen generation. ............................................................................... 47 3.2.3.2. Pyrolysis of partially matured source rock in isolation. ......................... 49 3.2.3.3. Pyrolysis of bitumen in isolation. .......................................................... 50 3.2.3.4. Pyrolysis of mixtures of partially matured source rock and bitumen (Recombined Mixture). ............................................................................................ 52 3.2.3.5. Whole rock pyrolysis. ............................................................................ 53 3.3. Gas analysis. .......................................................................................................... 55 3.4. Recovery of bitumen plus oil, partially matured source rock and coke.