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GEOL 553: Marine Sediments University of South Carolina Fall 2005. The Tools of Subsurface Analysis. Professor Chris Kendall EWS 304 kendall@sc.edu 777.2410. The Tools of Subsurface Analysis.

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GEOL 553: Marine Sediments University of South Carolina Fall 2005


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GEOL 553: Marine SedimentsUniversity of South CarolinaFall 2005

The Tools of Subsurface Analysis

Professor Chris Kendall

EWS 304

kendall@sc.edu

777.2410

GEOL 553 Lecture 3; Subsurface Analysis

the tools of subsurface analysis
The Tools of Subsurface Analysis

Facies analysis of subsurface data depends on tools which delimit of surfaces and provide clues as to the sediments they contain:

  • Well logs
  • Cores
  • Seismic
  • Gravity & magnetics

GEOL 553 Lecture 3; Subsurface Analysis

well logs versus seismic
Well Logs Versus Seismic
  • Well logs
    • Great vertical resolution
    • Delimit bounding surfaces
    • Establish lithology of sediments penetrated
  • Seismic
    • Great lateral continuity and resolution
    • Define gross sediment geometry

GEOL 553 Lecture 3; Subsurface Analysis

tools are keys to allostratigraphy sequence stratigraphy
Tools are Keys to Allostratigraphy & Sequence Stratigraphy
  • Allostratigraphy: bounding discontinuities including erosion surfaces, marine flooding surfaces, tuffs, tempestite, and/or turbidite boundaries etc. as time markers
  • Sequence Stratigraphy: higher level allostratigraphic model which interprets depositional origin of sedimentary strata as products of "relative sea level change"

GEOL 553 Lecture 3; Subsurface Analysis

the tools of subsurface analysis1
The Tools of Subsurface Analysis

Facies analysis of subsurface data depends on tools which delimit of surfaces and provide clues as to the sediments they contain:

  • Well logs
  • Seismic

GEOL 553 Lecture 3; Subsurface Analysis

well logs
Well Logs

Delimit of surfaces & identify sediments penetrated

  • Resistivity Logs
  • Spontaneous Potential (SP) Logs
  • Gamma Ray Logs
  • Neutron Logs
  • Density Logs
  • Sonic (acoustic) Logs

GEOL 553 Lecture 3; Subsurface Analysis

resistivity logs
Resistivity Logs

The most commonly used logs:

  • Measures resistance of flow of electric current
  • Is function of porosity & pore fluid in rock
  • Frequently used to identify lithology

GEOL 553 Lecture 3; Subsurface Analysis

spontaneous potential sp logs
Spontaneous Potential (SP) Logs

Next most common log

  • Measures electrical current in well
  • Result of salinity differences between formation water and the borehole mud
  • Separates bed boundaries of permeable sands & impermeable shales.

GEOL 553 Lecture 3; Subsurface Analysis

gamma ray logs
Gamma Ray Logs

Another common log

  • Records radioactivity of a formation
  • Shales have high gamma radioactive response
  • Gamma ray logs infer grain size (and so subsequently inferred depositional energy)
  • Gamma ray logs are most commonly used logs for sequence stratigraphic analysis

GEOL 553 Lecture 3; Subsurface Analysis

slide16
GEOL 553 Lecture 3; Subsurface Analysis

After Harris & Saller 1999

neutron logs
Neutron Logs

Another common log

  • Measures porosity of formation
  • Uses quantity of hydrogen present
  • Measures lithology when used with Density Log

GEOL 553 Lecture 3; Subsurface Analysis

density logs
Density Logs

A common log

  • Measures formation’s bulk density
  • Used as a porosity measure
  • Differentiates lithologies with Neutron Log
  • Used with Sonic Logs to generate synthetic seismic traces to match to seismic lines

GEOL 553 Lecture 3; Subsurface Analysis

sonic acoustic logs
Sonic (Acoustic) Logs

Another common log

  • Measures of speed of sound in formation
  • Tied to porosity and lithology
  • Used with Density Logs to generate Synthetic Seismic traces to match to Seismic lines

GEOL 553 Lecture 3; Subsurface Analysis

the tools of subsurface analysis2
The Tools of Subsurface Analysis

Facies analysis of subsurface data depends on tools which delimit of surfaces and provide clues as to the sediments they contain:

  • Well logs
  • Seismic

GEOL 553 Lecture 3; Subsurface Analysis

seismic
Seismic

Seismic stratigraphic interpretation used to:

  • Define geometries of genetic reflection packages that envelope seismic sequences and systems tracts
  • Identify bounding discontinuities on basis of reflection termination patterns and continuity

GEOL 553 Lecture 3; Subsurface Analysis

seismic boundaries
Seismic Boundaries

Termination below discontinuity, or upper sequence boundary:

  • Toplap termination
  • Truncation of sediment surface
  • Often channel bottom

Above a discontinuity defining lower sequence boundary:

  • Onlap over surface
  • Downlap surface

GEOL 553 Lecture 3; Subsurface Analysis

seismic boundaries1
Seismic Boundaries

Below Boundary - Toplap termination

GEOL 553 Lecture 3; Subsurface Analysis

seismic boundaries2
Seismic Boundaries

Below Boundary -Truncation of surface

GEOL 553 Lecture 3; Subsurface Analysis

seismic boundaries3
Seismic Boundaries

Channeled

Surface

– Below Boundary

GEOL 553 Lecture 3; Subsurface Analysis

seismic boundaries4
Seismic Boundaries

Over Boundary - Onlap onto surface

GEOL 553 Lecture 3; Subsurface Analysis

seismic boundaries5
Seismic Boundaries

Over Boundary- Downlap onto surface

GEOL 553 Lecture 3; Subsurface Analysis

sequence stratigraphy
Sequence Stratigraphy

Subdivision & interpretation of sedimentary record using a framework surfaces seen in outcrops, well logs, & 2-D and 3-D seismic.

Include:

  • Surfaces of erosion & non-deposition (sequence boundaries)
  • Flooding (trangressive surfaces [TS] &/or maximum flooding surfaces [mfs]) & high stand condensed surfaces

This framework used to predict the extent of sedimentary facies geometry, lithologic character, grain size, sorting & reservoir quality

GEOL 553 Lecture 3; Subsurface Analysis

tools define bounding surfaces
Tools Define Bounding Surfaces

These surfaces subdivide sedimentary rock &

provide:-

  • Relative time framework for sedimentary succession
  • Better understanding of inter-relationship of depositional settings & their lateral correlation

Conceptual models follow that link the processes that formed the sediments and enable the prediction of their gross geometries

GEOL 553 Lecture 3; Subsurface Analysis

hierarchy of geometries
Hierarchy of Geometries
  • Sequence geometries are subdivided and defined by
    • Maximum Flooding Surfaces (mfs)
    • Transgressive Surfaces (TS)
    • Sequence Boundaries (SB)
  • Define how vertical succession or stacking patterns of unconfined sheets are arranged
    • Prograde (step seaward)
    • Retrograde (step landward)
    • Aggrade (build vertically)
  • Sheets and unconfined lobes may contain
    • Non-amalgamated bodies
  • Amalgamated, multi-storied bodies
    • Incised topographic fill of valleys
    • Unconfined but localized lobes from point & multiple up dip sources
    • Unconfined but localized build ups (carbonates)

GEOL 553 Lecture 3; Subsurface Analysis

hierarchy of geometries1
Hierarchy of Geometries
  • Sequence geometries are subdivided and defined by
    • Maximum Flooding Surfaces (mfs)
    • Transgressive Surfaces (TS)
    • Sequence Boundaries (SB)
  • Define how vertical succession or stacking patterns of unconfined sheets are arranged
    • Prograde (step seaward)
    • Retrograde (step landward)
    • Aggrade (build vertically)
  • Sheets and unconfined lobes may contain
    • Non-amalgamated bodies
  • Amalgamated, multi-storied bodies
    • Incised topographic fill of valleys
    • Unconfined but localized lobes from point & multiple up dip sources
    • Unconfined but localized build ups (carbonates)

GEOL 553 Lecture 3; Subsurface Analysis

hierarchy of geometries2
Hierarchy of Geometries
  • Sequence geometries are subdivided and defined by
    • Maximum Flooding Surfaces (mfs)
    • Transgressive Surfaces (TS)
    • Sequence Boundaries (SB)
  • Define how vertical succession or stacking patterns of unconfined sheets are arranged
    • Prograde (step seaward)
    • Retrograde (step landward)
    • Aggrade (build vertically)
  • Sheets and unconfined lobes may contain
    • Non-amalgamated bodies
  • Amalgamated, multi-storied bodies
    • Incised topographic fill of valleys
    • Unconfined but localized lobes from point & multiple up dip sources
    • Unconfined but localized build ups (carbonates)

GEOL 553 Lecture 3; Subsurface Analysis

hierarchy of geometries3
Hierarchy of Geometries
  • Sequence geometries are subdivided and defined by
    • Maximum Flooding Surfaces (mfs)
    • Transgressive Surfaces (TS)
    • Sequence Boundaries (SB)
  • Define how vertical succession or stacking patterns of unconfined sheets are arranged
    • Prograde (step seaward)
    • Retrograde (step landward)
    • Aggrade (build vertically)
  • Sheets and unconfined lobes may contain
    • Non-amalgamated bodies
  • Amalgamated, multi-storied bodies
    • Incised topographic fill of valleys
    • Unconfined but localized lobes from point & multiple up dip sources
    • Unconfined but localized build ups (carbonates)

GEOL 553 Lecture 3; Subsurface Analysis

hierarchy of geometries4
Hierarchy of Geometries
  • Sequence geometries are subdivided and defined by
    • Maximum Flooding Surfaces (mfs)
    • Transgressive Surfaces (TS)
    • Sequence Boundaries (SB)
  • Define how vertical succession or stacking patterns of unconfined sheets are arranged
    • Prograde (step seaward)
    • Retrograde (step landward)
    • Aggrade (build vertically)
  • Sheets and unconfined lobes may contain
    • Non-amalgamated bodies
  • Amalgamated, multi-storied bodies
    • Incised topographic fill of valleys
    • Unconfined but localized lobes from point & multiple up dip sources
    • Unconfined but localized build ups (carbonates)

GEOL 553 Lecture 3; Subsurface Analysis

ebb ooid delta uae
Ebb Ooid Delta - UAE

GEOL 553 Lecture 3; Subsurface Analysis

delta mouth bar kentucky
Delta Mouth Bar - Kentucky

Note Incised Surface

GEOL 553 Lecture 3; Subsurface Analysis

channel gulf coast
Channel – Gulf Coast

Note Incised Surface

GEOL 553 Lecture 3; Subsurface Analysis

flood deltas channels kty
Flood Deltas & Channels - Kty

GEOL 553 Lecture 3; Subsurface Analysis

tidal channels khor al bazam uae
TidalChannelsKhor alBazam-UAE

GEOL 553 Lecture 3; Subsurface Analysis

tidal storm or tsunami channel
Tidal, Storm or Tsunami Channel

Note Incised Surface

GEOL 553 Lecture 3; Subsurface Analysis

tsunami load drape kty
Tsunami Load & Drape - Kty

Note Uniform Thickness of Layer

GEOL 553 Lecture 3; Subsurface Analysis

clastic sequence stratigraphic hierarchies
Clastic Sequence Stratigraphic Hierarchies

GEOL 553 Lecture 3; Subsurface Analysis

channels shelves
Channels & Shelves

Channel

Shelf

Both have unique processes & structures that can be used to identify their setting

GEOL 553 Lecture 3; Subsurface Analysis

tools enable sequence stratigraphic analysis
Tools Enable Sequence Stratigraphic Analysis

This analysis involves

  • Subdivision of section into sequences, parasequences and beds.
  • Link conceptual models with mix of components of the individual sequence, parasequence or beds
  • Use these to explain the depositional setting in terms of their lithology, grain size, sedimentary structures, contacts character (gradational, abrupt) etc

GEOL 553 Lecture 3; Subsurface Analysis

sequence stratigraphic analysis
SequenceStratigraphicAnalysis

GEOL 553 Lecture 3; Subsurface Analysis

end of the lecture

End of the Lecture

Can it be supper time?

unconfined flow not in a channel
Unconfined Flow - Not in a Channel
  • Unique Processes
    • Flow is in all directions
    • No lateral boundaries, only upper and lower boundaries
    • Velocity changes: high to low
  • Sediment responses
    • Decrease in grain size: Fining outward (coarse to fine)
    • Erosional/sharp/gradational contacts
    • Accretion: Downstream, upstream and vertical
    • Decrease in sedimentary structures away from source
  • Geometries
    • Sheets
    • Thin in direction of flow

GEOL 553 Lecture 3; Subsurface Analysis