Geology _ Geophysics in Oil Exploration

Greywackeisaheterogeneousmixtureoflithicfragmentsandan

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Unformatted text preview: sitional Sedimentary Structures: • Bedding & Lamination • Current Ripples, Sand dunes, Wind ripples • Post Depositional Sedimentary structures: • Slump Structures & Load Casts • Biogenic Sedimentary Structures Types of Sediments: 1. 2. 3. 4. 5. 6. 7. Terrigenous clastic sediments Carbonate Rocks Evaporites Ironstones Phosphate deposits Siliceous sediments Volcanic Rocks 1‐Terrigenous Clastic Sediments A‐Sandstones: Sandstone (sometimes known as Arenite) is a sedimentary rock composed mainly of sand‐sized minerals or rock grains. Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, gray and white. Cement is Light colored CaCO3 & Red Iron Oxide There are many types of Sandstones such as • Black Sandstone: if Sand contain Tin Oxide • Argillaceous S.S.: if Sand contain Clay • Calcareous S.S.: if Sand contain CaCO3 Grain Supported Sandstones: (Arenite) • Arenite: when Qz > 90% • Arkosic Arenite: Feldspar > 25% & exceeds the rock fragment content • Lith Arenite: Feldspar > 25% but less rock fragment content • Phyll Arenite: is Lith Arenite but rock fragments are Shale or Slate • Calc Lithite: is Lith Arenite but rock fragments are Limestone 6 Geology & Geophysics in Oil Exploration Mahmoud Sroor Groove Marks Flute Marks Geology & Geophysics in Oil Exploration Matrix Supported Sandstones: (Wacke) • Wacke or Dirty Sandstone: when Matrix>30% • Grey Wacke: is a heterogeneous mixture of lithic fragments and angular grains of quartz and feldspar • Arkosic Wacke: Arkose with proportion of Matrix Hybrid Sandstones: (S.S. which contain non clastic components) • Glauconitic S.S.: Glauconite occurs as sand‐sized Pellets • Phosphatic S.S.: Phosphate may be present as a cement, coprolites, or bone fragments • Calcareous S.S.: Terrigenous clastics cemented by Calcite B‐Conglomerates: Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated...
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