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Clastic Sedimentary Rocks
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Robert Gordon University 1
Lecture 3b: Dynamic Earth: Clastic
Sedimentary Rocks
Sedimentary rocks = reservoir rocks, seals and source rocks
ENM200: Dynamic EarthDr Bryan T Cronin ([email protected])
Robert Gordon University 2Sedimentary Rocks
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Clastic sedimentary rocks (e.g. sandstones, mudstones, conglomerates.are made of material eroded from one place then transported to and depositedin another.
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The Rock CycleThe RockCycle
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Mechanical weathering
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Mechanical weathering: frost wedging
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Mechanical weathering:material is eroded (usuallyby frost wedging) then movesprogressively down the drainage system (rivers etc)
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Chemical weathering
Chemical weathering includes dissolution (particularly of limestones) and rusting (oxidation)
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Chemical weathering of these sandstone blocks has attacked the cement between the grains, so that they become loose and fall out. The sandstone is more strongly cemented along closely-spaced beds (sand layers) and the sides of small joints or cracks in the rock. The overall effect is to produce a pock-marked surface which is sometimes called honeycomb weathering.
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Weathering of different materials
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High porosity (x43 on A4)
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Low porosity (x31 on A4)
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Conglomerate:
Dunnottar Castle, Stonehaven,Aberdeenshire
Robert Gordon University 17Polymict Conglomerate
Robert Gordon University 18Litharenite (sandstone)
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Kimmeridge Clay mudstones (grey and limestones (yellow), at Kimmeridge Bay, Dorset, England. This is the main oil-prone source rock of the North Sea
Robert Gordon University 20Mudstone under the microscope
Robert Gordon University 21Biosparite
Robert Gordon University 22Diapric anhydrite
Robert Gordon University 23Triassic Anhydrite
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Sedimentary structures
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Fluvial
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SANDSTONE RESERVOIRS
Introduction to environment section:
Depositional Environments and a simplified classification
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Depositional Environment
ContinentalAeolianAlluvial fanFluvialLacustrineGlacial
MarineMarginal/ParalicShelfSlopeBasin
Controls on the size, shape and production characteristics of reservoir bodies
Major effects on reservoir quality distribution: Porosity Permeability Net to Gross Ratio Connectivity/Compartmentalisation
Identification in the subsurface, use of well logs, cores and cuttings
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Sedimentary Environments
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Sandstone Reservoirs Alluvial Fan
Schematic model
Modern Example
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Sandstone Reservoirs - FluvialBraided River Meandering River
Outcrop
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Braided River log response (subsurface)
Sandstone Reservoirs - Fluvial
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Sandstone Reservoirs - Lacustrine
Schematic
Pyramid Lake, Nevada
We will examine lacustrine environmentsprimarily in association with alluvialfans and fluvial sandstone reservoirs
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Sandstone Reservoirs - Lacustrine
Eocene Green River Fm., Utah, USA
SOURCE ROCKS
Lacustrine algal carbonate
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Sandstone Reservoirs Aeolian Modern
Analogue for Southern North Sea Rotliegend (Permian) Gas Fields
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Sandstone Reservoirs Aeolian subsurface: Leman Field, southern North Sea
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Sandstone Reservoirs - DeltaicSchematic Delta Components
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Sandstone Reservoirs Littoral
Barrier Island
Galveston Island, Texas, USA
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Sandstone Reservoirs
Littoral
Map of Aux Vases foreshore and tidal channel sands, Carboniferous, Illinois, USA
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Idealised Turbidite Depositional Sequences
Sandstone Reservoirs Deep Marine
Retrogradational fans Progradational fans
Turbidite:Bouma Sequence
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Reservoirs: A Simplified Classification
Aeolian
FluvialLacustrineGlacial
shelfslope
basin
Turbidites, Talus, Gravitydeposits
littoral
deltaAlluvial Fan
5 PRINCIPAL TYPES OF RESERVOIR
5 PRINCIPAL TYPES OF DEPOSITIONAL ENVIRONMENT
Sandstone, Limestone, Chalk, Dolomite, Others
Continental, Marine Littoral Deltaic, marine Littoral non-Deltaic, Marine Shelf,Deep-marine
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Lecture 3b: Dynamic Earth: Clastic Sedimentary RocksThe Rock CycleMechanical weatheringMechanical weathering: frost wedgingChemical weatheringWeathering of different materialsHigh porosity (x43 on A4)Low porosity (x31 on A4)Sedimentary structuresFluvialSANDSTONE RESERVOIRSDepositional EnvironmentSedimentary EnvironmentsSandstone Reservoirs Alluvial FanSandstone Reservoirs - FluvialSandstone Reservoirs - LacustrineSandstone Reservoirs - LacustrineSandstone Reservoirs Aeolian ModernSandstone Reservoirs Aeolian subsurface: Leman Field, southern North SeaSandstone Reservoirs - DeltaicSandstone Reservoirs LittoralSandstone Reservoirs LittoralSandstone Reservoirs Deep MarineReservoirs: A Simplified Classification