Paragenetic History of the Ordovician Trenton Group Carbonates, Southwestern Ontario

Paragenetic History of the Ordovician Trenton Group Carbonates, Southwestern Ontario by Ian M. Colquhoun, B.Sc. A Thesis submitted to the Department of Geological Sciences in partial fulfillment of the requirements for the degree of Master of Science January 1991 Brock University St. Catharines, Ontario © Ian Colquhoun, 1991 The author has agreed that the Department of Geological Sciences, Brock University, may make this thesis freely available for inspection. Moreover, that permission for extensive copying of the thesis for scholarly purposes may be granted by the Chair of the Department of Geological Sciences. It is understood that due recognition will be given to the author of this thesis and to Brock University in any use of material in this thesis. Copying or duplication or any use of the thesis for financial gain without approval by Brock University (or the author's written permission) is prohibited. Requests for permIssIOn to copy or to make other use of material in this thesis in whole or in part should be addressed to: Chair, Department of Geological Sciences, Brock University, S1. Catharines, Ontario, Canada. L2S 3Al 1 Abstract Geochemical examination of the rock matrix and cements from core material extracted from four oil wells within southwestern Ontario suggest various stages of diagenetic alteration and preservation of the Trenton Group carbonates. The geochemical compositions of Middle Ordovician (LMC) brachiopods reflect the physicochemical water conditions of the ambient depositional environment. The sediments appear to have been altered in the presence of mixed waters during burial in a relatively open diagenetic microenvironment. Conodont CAl determination suggests that the maturation levels of the Trenton Group carbonates are low and proceeded at temperatures of about 30 - 50°C within the shallow burial environment. The Trenton Group carbonates are characterized by two distinct stages of dolomitization which proceeded at elevated temperatures. Pre existing fracture patterns, and block faulting controlled the initial dolomitization of the precursor carbonate matrix. Dolomitization progressed In the presence of warm fluids (60 75°C) with physicochemical conditions characteristic of a progressively depleted basinal water. The matrix is mostly Idiotopic-S and Idiotopic-E dolomite, with Xenotopic-A dolomite dominating the matrix where fractures occur. The second stage of dolomitization involved hydrothermal basinal fluid(s) with temperatures of about 60 - 70°C. These are the postulated source for the saddle dolomite and blocky calcite cements occurring in pore space and fractures. Rock porosity was partly occluded by Idiotopic-E type dolomite. Late stage saddle dolomite, calcite, anhydrite, pyrite, marcasite and minor sphalerite and celestite cements effectively fill any remaining porosity within specific horizons. Based on cathode luminescence, precipitation of the different diagenetic phases probably proceeded in open diagenetic systems from chemically homogeneous fluids. Ultraviolet fluorescence of 11 the matrix and cements demonstrated that hydrocarbons were present during the earliest formation of saddle dolomite. Oxygen isotope values of -7.6 to -8.5 %0 (PDB), and carbon isotope values of - 0.5 and -3.0 %0 (PDB) from the latest stage dog-tooth calcite cement suggest that meteoric water was introduced into the system during their formation. This is estimated to have occurred at temperatures of about 25 - 40°C. Specific facies associations within the Trenton Group carbonates exhibit good hydrocarbon generating potential based on organic carbon preservation (1-3.5%). Thermal maturation and Lopatin burial-history evaluations suggest that hydrocarbons were generated within the Trenton Group carbonates some time after 300 Ma . Progressively depleted vanadium trends measured from hydrocarbon samples within southwestern Ontario suggests its potential use as a hydrocarbon migration indicator on local (within an oilfield) and on regional scales. 111 Acknowledgements I am indebted to Telesis Oil and Gas Ltd. for funding this research, through a grant to Professor Uwe Brand, and for kindly making information relative to this research freely available. I also wish to acknowledge funding of part of this thesis through equipment grants, from NSERC (0043282) and URIF ( BRll-OOl) and NSERC Operating grant A7961 to Dr. Uwe Brand. I am especially grateful to my supervisor, Professor Uwe Brand, for his professional contributions to this thesis. I would also like to thank him for the thorough education that he has provided. I would like to extend gratitude to Allan R. Phillips (Kerr-McGee Corporation) and Steven A. Colquhoun (Telesis Oil and Gas Ltd.) for the experience of working with them on the preparation of the B. A. Liberty Memorial Core Workshop, Cores of the Trenton-Black River, for the Ontario Petroleum Institute Annual Meeting held in November of 1989. This professional co-operation led to the development of the subsurface facies analysis presented in this thesis. I also appreciate the help given me by the staff, and the interest In my work expressed by the management, of Telesis Oil and Gas Ltd. Thanks is extended to the Ministry of Natural Resources in London Ontario, particularly Terry Carter, for the co-operation and use of their facilities, and to Professor Anita Harris (Case Western University) for providing the type-Ordovician conodont samples. At Brock University, Professor M. Manocha of the Department of Biological Sciences generously allowed me use of the ultraviolet fluorescence microscope. From the Department of Geological Sciences, special thanks to William Parkins for help and advice with the conodont extractions, and Professor J aan Terasmae for use of the facilities in the Palynology Laboratory. Departmental technicians Candace Kramer and lV Mike Lozon are thanked for special efforts and assistance above their normal duties. I also acknowledge my parents who have supported me both morally and financially over the years. Finally, the most important of all the people in my life to date has been the friendship and love given to me from Maria Goulbourne. We have come a long way together. I thank you for being there for me time after time and for the unselfish love that has grown over the last two years. v Table of Contents Page No. Abstract 1 Acknowledgements 111 Table of Contents v List of Figures IX List of Tables Xl List of Plates X11 Introduction 1 History of Oil and Gas Discovery Pre-Hillman Discoveries 4 Essex County/Hillman Discoveries 6 Background-General Geology 8 Paleoenvironments of the Trenton-Black River sediments 8 Structural review of the Michigan Basin within southwestern Ontario 13 Structural similarities recognized m Michigan Basin Hydrocarbon Reservoirs 1 8 Theoretical Background: Carbonate Geochemistry 20 Stable Isotope Geochemistry 22 Isotopic variations of Geological Relevance Carbon isotopic variations 22 Oxygen isotopic variations 23 Use of stable isotopes in the analysis of ancient carbonates 24 Dolomitization 25 Burial Compaction Model 26 VI Table of Contents Page No. Sabhka and Coorong Models 27 Mixed Water Model 27 Pressure Solution Model 28 Hydrothermal or Saddle Dolomite 29 Dedolomite 3 1 Thermal Maturation Conodont Colour Alteration Studies 32 Limitations with the CAl determination 33 Host rock maturation 33 Evaluation of Hydrocarbon Potential 34 Geoporph yrin s 36 Application to Hydrocarbon Geochemistry 39 Analytical Techniques: Part 1: Petrographic Analyses Light Microscopy 41 Cathodoluminescence 41 Ultraviolet Fluorescence 42 Part 2: Geochemical Analyses Rock and Cement Trace Element Determination 42 Shale Trace Element Determination 44 Brine and Oil Trace Element Determination 44 Organic Carbon and Leco Sulphur Determination 46 Part 3: Stable Isotope Analyses Rock and Cement Stable Isotope Determination 47 Oxygen and Deuterium Determination of the Brines 47 Part 4: Thermal Maturation Analysis 48 Petrographic Analyses: Results and Discussion Part 1: Light Microscopy: Discussion of Dolomite Textures 49 Dolomite Matrix 49 vii Table of Contents Page No. Idiotopic-S Dolomite Texture 52 Idiotopic-E Dolomite Texture 54 Xenotopic-A Dolomite Texture 56 Saddle Dolomite 57 Dedolomite 57 Silica 57 Stylolites 60 Pyrite and Anhydrite 60 Calcite, Sphalerite, and Celestite 62 Porosity and Permeability 66 Part 2: Cathodoluminescence 68 Part 3: Ultraviolet Fluorescence 72 Geochemical Results and Discussion Calcium and Magnesium 75 Strontium 75 Sodium 76 Covarient Trace Element Trends Strontium and Sodium 77 Strontium and Manganese 77 Limestone Diagenesis Trace Element Trends 78 Stable Isotope Trends 8 1 Dolomitization Trace Element Trends 84 Stable Isotope Trends 86 Saddle Dolomite and Calcite Cements Trace Element Trends 88 Stable Isotope Trends 93 Evidence for Dolomitization and Cement formation during burial at elevated temperatures 9 9 Estimate temperature of diagenetic pore fluids using a18 0 100 VI11 Table of Contents Page No. Geochemistry of Formation Waters Trace Element Trends 102 Stable Isotope Trends 111 Thermal Maturation Analysis: Results and Discussion 114 Reconstruction of the Ancient Geothermal Gradient 119 Thermal Maturation and Lopatin Basin Modeling 122 Evaluation of Hydrocarbon Potential: Results and Discussion 126 Hydrocarbon Geochemistry: Results and Discussion 136 Dolomitization Model and Reservoir Development Early Burial History 147 Dolomitization Model 147 Evidence for Mississippi Valley-type processes In the Michigan Basin 149 Summary of Results Evolution

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