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Dr. Tark Hamilton Camosun College

Sedimentary Geology Geos 240 – Chapter 2 Collecting the Data Part 1 Geological, Stratigraphic & Petrophysical Data. Dr. Tark Hamilton Camosun College. Collecting the Data. Stratigraphic Sections from Surface Outcrops Petrophysical logging of boreholes Well cuttings and cores

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Dr. Tark Hamilton Camosun College

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  1. Sedimentary GeologyGeos 240 – Chapter 2Collecting the DataPart 1 Geological, Stratigraphic & Petrophysical Data Dr. Tark Hamilton Camosun College

  2. Collecting the Data • Stratigraphic Sections from Surface Outcrops • Petrophysical logging of boreholes • Well cuttings and cores • Regional Geophysics • Labwork on sediments, rocks, fossils, fluids • Computer/Office: Mapping, Interpretation & Modelling

  3. Measuring a Stratigraphic Section Gayna River near Norman Wells NWT Western Canada Sedimentary Basin

  4. Measuring with a Jacob’s Staff • Use a 1.5 m stick with a level or dip arrow • Site along to next 1.5 m position in true thickness position and add! • One potato two potato three potato four!, Five potato Six potato…

  5. Strip Log – Stratigraphic Section • Grain Size increases to right = resistance to weathering • Sands>> stick out while Shales<< are recessive

  6. Castlegate Sandstone: Utah • Horizontal Photos & Line Drawing showing bedding, sequence boundaries & paleocurrent directions • ~1 week’s work

  7. Components of a Modern Exploration Rig on Land

  8. Drilling Details:Mud Lubricates, Cools, Prevents Blowouts, Carries Cuttings & Fluids

  9. Roller Bits For Various Hole Sizes • For Hard Rocks (Sandstones & Limestones) • Blade Bits are used for clays, coals and soft shales

  10. Core, Core Boxes & Cuttings • Description is the major work of most wellsite geologists • Core “libraries” at ISPG Calgary & Charlie Lake, NEBC

  11. Coring Tools: Full Core & Sidewall

  12. Energy Resources Conservation Board: ISPG & University of Calgary

  13. Detailed Well Log • Formation Symbols at Left, SP & Gamma Logs • Lithologic interpretation, Detailed descriptions

  14. Table of Petrophysical Logs Fluids vs Rock Brine, Gas, Oil Logs vary w/Diam Low Dens Coal Salts FMS TV Pictures Sedimentary structures XRF Induced Gamma Ray Fluorescence Chemistry/Mineralogy

  15. Physical Properties of Formation near a Borehole • Drilling Fluids: mud, salts, ions, water move

  16. Natural Gamma Measures Shaliness due to 40K in clay minerals Nunavut

  17. Common Petrophysical Logs: SP • Shales have + SP response, high CEC, Na+ moves into mud • Permeable Sands have –SP response. Cl- is more mobile as mineral surfaces are negatively charged (silicates)

  18. Petrophysical Logging: SP & Resistivity • SP –Sand line to left, +Shale Line to right • Resistivity tool has different depths of penetration

  19. Petrophysical Logs: Caliper & Resistivity • Shales are soft so hole cuts to a bigger diameter Mudcake Fresh Water Invasion Mudcake

  20. Petrophysical Logs: Neutron & Density

  21. Petrophysical logs: Dipmeter & FMS

  22. Channel Sands in Shales Sands L.Cretaceous Jurassic

  23. THIS COVERS MOST CONVENTIONAL SEDIMENTARY GEOLOGY FOR RESOURCE EXPLORATIONEnd of Chapter 2 Part 1 (Strata, Sedimentary Rocks & Well Logs) • Mining Exploration, Environmental, Geotechnical, Aquifer, Academic & Archeological studies all do similar things but with smaller tools, areas of interest and way smaller budgets!

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