4 What controls sediment supply? and Basin Types

Tectonics (need to fill a hole!) and Climate 1. Rift - Stretch therefore rapid subsidence, then decrease profile 2. Passive Margin - Continued extension, creates oceanic crust (constructional and starved passive margins) 3. Strike - Slip - Flower Structures 4. Foreland - Loading causes subsidence eg. south falkland basin

- Hydrophones (offshore) - Geophones (onshore)

4 What does seismic allow us to do?

1. Identify potential targets 2. Understand geological history of region 3. Identify potential hazards 4. Quantify potential resources

- Source - Migration pathway - Reservoir - Seal - Trap

Geology Basins Flashcards by Daniel Milner-Smith

What controls sediment supply?
and Basin Types

Tectonics (need to fill a hole!) and Climate

Rift - Stretch therefore rapid subsidence, then decrease profile
Passive Margin - Continued extension, creates oceanic crust (constructional and starved passive margins)
Strike - Slip - Flower Structures
Foreland - Loading causes subsidence eg. south falkland basin

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What creates the waves for seismic?

Hammer and dynamite (onshore)
Airgun (offshore)

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Seismic Receivers

Hydrophones (offshore)
Geophones (onshore)

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Seismic Recorders

Seismograph

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What does seismic data present?

The measured changes in density through changes in velocity of seismic waves

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What does seismic allow us to do?

Identify potential targets
Understand geological history of region
Identify potential hazards
Quantify potential resources

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Seismic Strat.
How would you identify Onlap/Offlap

Dip less than surface they terminate on

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Seismic Strat
How would you identify Down lap

Dip greater than surface they terminate on

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Seismic Strat
How would you identify Toplap

Dip greater than surface at which they terminate. Mirror of downlap

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Play requirements

Source
Migration pathway
Reservoir
Seal
Trap

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Play Concept
Source

Sed. rock - sufficient organic mats
1st Carbs and proteins, then lipids and ligins
Oil and gas from aqueous - mainly gas from terrestrial
- Sed. decreases therefore increase concentration organic matter
- Anoxic environment therefore lack of circulation

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Main source rock depositional environments

lacustrine eg. green river formation, Utah
Delta eg. Missionary bay Mangroves
Deep Marine eg. Black sea

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What are the key types of well data?

Core, Mud logging, and wireline

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Play Concepts
What is Primary Migration

Flow out of source
Low permeability: fracture in source promote expulsion
Kerogen to petroleum = increase vol. therefore promiotes micro-fracturs and increase pA

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What does Gamma ray show?

Quantities of K, Th, and U within rocks
Low values usually sandstone, high values usually shale
Help to understand depositional environment

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Play Concepts
What is Secondary Migration

Flow from sources
HCs more buoyant that water and decrease solubility
therefore drives migration

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What does Neutron Data show?

Indicates porosity by No. hydrogen atoms
Hydrogen present in water and HCs
Count rate is low in high porosity rocks, and high in low porosity rocks
(where less H, neutrons bounce back therefore high return, where more H, neutrons scatter, therefore less return)

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Play Concepts
Reservoir requirments?

Porous and permeable

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Play Concepts
What can the reservoir be affected by?

Cementation/Compaction

How heterogenous are units? (How dif.?)

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Play Concept
Other Reservoir info?

Dissolution of limestone can create reservoir
Darcy units used to measure perm.
- 1 Darcy = very good res. Nichols 2009

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Play Concepts
What are the best reservoirs?

Well sorted sandy desserts
Shallow seas
Oolittic Grainstones
Boundstones

(Less important)
- Rivers
- Deltas
- Submarine fans

Presence of mud and cementation decreases porosity

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What does Density data show?

Gamma rays emitted
Collide with electrons
Scatter
Returning rays counted
High bulk density = lots of electrons = scattering = low return rate

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Play Concepts
What makes a seal effective?

Low porosity and permeability
Capillary pressure greater than buoyancy pressure
Regionally extensive
Ductile (bends not fracture)

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Play Concepts
What are the best seals?

Fine grained sediments (shales) greater gamma
Evaporates (can move) very low gamma

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Play concepts Structural Traps

1. Anticlinal (no fractures?) 2. Salt dome (future movement?) 3. Fault trap (Clay smearing? Cataclasis?)

Play Concept What is a trap?

Conc. of HCs

Play Concept Stratigraphic traps

1. Pinchout 2. Unconformity 3. Reef

What can be done with Neutron Density Data

-Both used together for accurate evaluation of porosity -Where they track together = Sst -Where they are separate = different lithologies or gas -Where there is gas - density log values are high and neutron log values are low -Use with Gamma rays for better understanding

3 key types of explorations

-buy into existing field -explore other parts of an identified producing region -explore new region

Pros and cons of buying into existing field

Pros: -high success rate -good infrastructure Cons: -high buy in costs -low potential returns

Pros and cons of exploring others parts of identified region

Pros: -good understanding of existing system -lots of potentially cheaper data Cons: -more difficult targets -lower potential returns

Pros and cons of exploring new region

Pros: -potentially high returns Cons: -high risk -limited existing data therefore expensive

How can gravity help search for HCs

-Stage 1 of investigations -Variations in r alters observed g -Underlying densities change observed g -Therefore can identify anomalies -Can make assumptions about subsurface when comparing to observed measurements -Oil can produce a gravity low -Cost effective way of getting regional data -Used IF substantial density contrasts are expected

What has an influence on heat flow

-crustal thinning -mantle upwelling -water circulation -sills and dykes -salt -the rocks themselves -can effect oil window

Features: -Rootlets upper tidal flats -Flaser/lenticular bedding -Ripple cross lamination -Heterolithic Strat. -Bi-directional herringbone

Tidal Estuary - Coastal

Features: -Mouth bar deposits - well sorted -Delta plain = fine grained sand, interbedded with silt -Beach = wave ripples and medium sand -Delta front = mudstone interbedded with sand and bioturbation

Wave dominated delta - Delta

Features: -Bi-directional features, herringbone -Mud drapes during slack water

Tidal Dominated Coast - Coastal

Features: -Inner shelf grain/packstone -Outer shelf pack/whackstone -Slope redeposited limestone -Shelf edge grainstone shoals -Slump deposits -Deep water carbonate

Non-rimmed Carbonate shelf - Shallow Marine Carbonate

Features: Boundstone at top -Forereef slope rudstone and redeposited limestone -Slump deposits -Pelagic and Carbonate mudstone turbidites further out

Carbonate Rimmed Shelf - Shallow Marine Carbonate

Features: -Grain Stones shoals in top -Ooids -Bioclastic Material -Mid-ramp redeposited material -Outer-ramp mud/wackstone

Carbonate Ramp - Shallow Marine

Feautures: -Delta Plain = Fine grained sand and silt with current ripples -Delta channels = medium sand with current ripples -Moth bar = massive medium sand -Delta front = bioturbation, slumping structures, fossils

River Dominated Delta - Delta

Features: -Beach = medium sand -Estuary mouth = cross bedding, fossils and current ripples -Central lagoon = bioturbation and limestone -Bay head delta = cross strat and bioturbation

Wave dominated Estuary - Coastal

Features: -Shoreface = cross strat. and bedded sands -Reworked sands before tidal currents and storms -Offshore transition zone = hummocky cross-strat., interbedded with bioturbated mud -Offshore = bioturbation, mudstone

Tidal Influenced Shelf succession - Shallow Marine

Features: -Cross-strat. -Mud drapes -Bi-directional features, herringbone

Tidal Dominated Delta - Delta

Features: -Shoreface = wave ripples and swale -Offshore transition = thin sheets mud and sst, hummocky cross-strat -Offshore = bioturbation

Storm Dominated Shelf - Shallow Marine

Features: -Grading up into finer grained deposit -Matrix or clast support where cobbles and boulders embedded in fine sediment

Debris Flow - Deep Marine

Features: -Rootlets, muds and sands -Channel fill succession of TxB sands -Fining upwards -Lateral accretion surfaces -Scoured channel base -Finer grain sizes than a Braider River

Meandering River - Fluvial

Features: -Mix of sand, gravel, and mud -Inner fan = thick conglomerate and sst turbidites -Thin levee deposits -Mid fan = coarsening up succession of sandy turbidites -Distal fan = fine grained turbidites

Submarine Fans - Deep Marine

Features: -Rootlets -Fine sand and muds -Trough cross bedding in channels, fining up -Coarsest sediments lower flat laminated -Scoured channel base

Braided River - Fluvial

Features: -Depositional couplets (alternating fine and course material) -Antidunes upstream -Clast imbrication -Poorly sorted silt and clay

Alluvial Sheetflood deposit - Alluvial

Features: -Disc structures -Laminated and cross-bedded sand -Pebbly and water escape structures -Reverse grading at bottom of sequence

Lowe Sequence Turbidite Flow - Deep marine

Features: -Matrix supported -Crude clast imbrication of bigger clasts -Poorly sorted

Debris Flow - Alluvial

Features: -Muds and wave rippled sands -Deeper laminated dark shales -Thin turbiditic sands

Lacustrine Deposit - Lacustrine

Features: -Cross laminated sands and ripples -Parallel laminated sands -Massive sands and granules rapidly deposited under upper flow regime -Scoured erosional base

Bouma Sequence Turbidite Flow - Deep Marine

What is the control on marine sedimentation?

Base level (sea level)

What is progradation (normal)

S>A Level, seaward

What is progradation (forced regression)

S>A where sea level lower Down, seaward

What is retrogradation

A>S where sea level rises Up, Landward

What is aggradation

A=S where sea level rises Up, static

What is Sequence Stratigraphy

"study of stratal stacking patterns and changes thereof in a time framework" (Catuneanu et al. 2009)

What is a Sequence Boundary (SB)

-The surface in which the first signs of erosion occur due to sea level fall -From aggradation to progradation (forced)

Highstand System Tract (HST)

-Sea level rising -Steep curve steadying out Therefore aggradation (where steep), then progradation (where levels out)

Falling Stage System Tract (FSST)

-Fluvial systems incise and transport sediment basinwards -Downward shift in facies (foreshore lies on offshore transition with SB between)

Lowstand System Tract (LST)

-Relative sea level at min -Sea level begins to rise (limited) - therefore Accom. -Progradational to Aggradational -Onlapping, clinoforms that thicken updip

Transgressive Surface (TS)

-A>S (where Supply is constant) -Sedimentation migrates landward -TS marks sea level rise

Transgressive System Tract (TST)

-Sea level rise increases -A>S (supply is constant) -Retrogradational -Onlap, clinoforms thicken landward

Maximum Flooding Surface (MFS)

-Hiatus in deposition occurs -Surface above which is MFS -The most landward region of the marine realm

Allogenic

Basin wide World Wide

Autogenic

within system

Two types of Geothermal systems

-High temp >180C -Low temp <100C

Two Shallow Geothermal Energy Soruces

-Heat pumps - Open loop and closed loops. Open is heat exchange with groundwater. Closed is heat exchange from installed boreholes. Local Scale Heating -Mine water systems - Old mines, storage and pathways for water, heated water extracted, boreholes used. e.g. Heerleen, Netherlands. Midland Valley, Scotland (Glasgow. Adams et al. 2009)

Geothermal Energy facts

-Volcanic activity -Water pumped to hot granites -Requires permeability (fractures) -Can be natural fractures or fracking

Three components to Geothermal Energy

Heat, Water, Permiability

Geothermal Potential UK

-26C/Km gradient -3000m depth would be 88C -Post carboniferous sed basins best Eden Project - hot granite under Cornwall

Where is hydrogen found

Water, HCs (most effective), organic matter

What is hydrogen used for

burned as combustible fuel, or fuel cells

Hydrogen Storage

-reservoir -cap (ductile and high capillary pA) -Trap structure -Salt caverns can be used -seal needs to be better quality than for HCs as higher buoyancy pA/>leak ability

Where is CO2 critical at?

31C and 7.38MPa

What is needed for CCS

Reservoir, Seal, Trap

What infrastructure is in place after HCs

Rigs, Wells, Pipelines

UK CCS example

Teeside, South Wales, Grangemouth, Acorn Project in North Sea

Requirements for Nuclear Waste Storage

Space, no migration, stable groundwater, no protected areas, wont be affected by future climates

Three types of Nuclear Storage Rock Types

-Salt as impermeable -Low strength - low permeability clays and mudstone -High strength - low permeability granites/slates

Other nuclear storage requirements

Depth of 200-1000m Thickness of 10s of metres Several kms wide

Geology Basins Flashcards

UofG Basins elective 2023