Slides 3b Clastic Sedimentary Rocks 2010

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


Clastic sedimentary rocks (e.g. sandstones, mudstones, conglomerates.are made of material eroded from one place then transported to and depositedin another.


The Rock CycleThe RockCycle


Mechanical weathering


Mechanical weathering: frost wedging

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Mechanical weathering:material is eroded (usuallyby frost wedging) then movesprogressively down the drainage system (rivers etc)


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.


Weathering of different materials


High porosity (x43 on A4)


Low porosity (x31 on A4)


Conglomerate:

Dunnottar Castle, Stonehaven,Aberdeenshire

Robert Gordon University 17Polymict Conglomerate

Robert Gordon University 18Litharenite (sandstone)


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


Sedimentary structures


Fluvial


SANDSTONE RESERVOIRS

Introduction to environment section:

Depositional Environments and a simplified classification


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


Sedimentary Environments


Sandstone Reservoirs Alluvial Fan

Schematic model

Modern Example


Sandstone Reservoirs - FluvialBraided River Meandering River

Outcrop


Braided River log response (subsurface)

Sandstone Reservoirs - Fluvial


Sandstone Reservoirs - Lacustrine

Schematic

Pyramid Lake, Nevada

We will examine lacustrine environmentsprimarily in association with alluvialfans and fluvial sandstone reservoirs


Sandstone Reservoirs - Lacustrine

Eocene Green River Fm., Utah, USA

SOURCE ROCKS

Lacustrine algal carbonate


Sandstone Reservoirs Aeolian Modern

Analogue for Southern North Sea Rotliegend (Permian) Gas Fields


Sandstone Reservoirs Aeolian subsurface: Leman Field, southern North Sea


Sandstone Reservoirs - DeltaicSchematic Delta Components


Sandstone Reservoirs Littoral

Barrier Island

Galveston Island, Texas, USA


Sandstone Reservoirs

Littoral

Map of Aux Vases foreshore and tidal channel sands, Carboniferous, Illinois, USA


Idealised Turbidite Depositional Sequences

Sandstone Reservoirs Deep Marine

Retrogradational fans Progradational fans

Turbidite:Bouma Sequence


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


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

Slides 3b Clastic Sedimentary Rocks 2010

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