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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 Regional Geophysics Labwork on sediments, rocks, fossils, fluids Computer/Office: Mapping, Interpretation & Modelling Measuring a Stratigraphic Section Gayna River near Norman Wells NWT Western Canada Sedimentary Basin 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… Strip Log – Stratigraphic Section Grain Size increases to right = resistance to weathering Sands>> stick out while Shales<< are recessive Castlegate Sandstone: Utah Horizontal Photos & Line Drawing showing bedding, sequence boundaries & paleocurrent directions ~1 week’s work Components of a Modern Exploration Rig on Land Drilling Details: Mud Lubricates, Cools, Prevents Blowouts, Carries Cuttings & Fluids Roller Bits For Various Hole Sizes For Hard Rocks (Sandstones & Limestones) Blade Bits are used for clays, coals and soft shales Core, Core Boxes & Cuttings Description is the major work of most wellsite geologists Core “libraries” at ISPG Calgary & Charlie Lake, NEBC Coring Tools: Full Core & Sidewall Energy Resources Conservation Board: ISPG & University of Calgary Detailed Well Log Formation Symbols at Left, SP & Gamma Logs Lithologic interpretation, Detailed descriptions Table of Petrophysical Logs Fluids vs Rock Brine, Gas, Oil Logs vary w/Diam Low Dens Coal Salts FMS XRF TV Pictures Induced Gamma Ray Fluorescence Sedimentary structures Chemistry/Mineralogy Physical Properties of Formation near a Borehole Drilling Fluids: mud, salts, ions, water move Natural Gamma Measures Shaliness due to 40K in clay minerals Nunavut 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) Petrophysical Logging: SP & Resistivity SP –Sand line to left, +Shale Line to right Resistivity tool has different depths of penetration Petrophysical Logs: Caliper & Resistivity Mudcake Fresh Water Invasion Mudcake Shales are soft so hole cuts to a bigger diameter Petrophysical Logs: Neutron & Density Petrophysical logs: Dipmeter & FMS Channel Sands in Shales Sands L.Cretaceous Jurassic THIS COVERS MOST CONVENTIONAL SEDIMENTARY GEOLOGY FOR RESOURCE EXPLORATION End 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!