1. Professor Chris Kendall
GEOL 553: Marine Sediments University of South Carolina Fall 2005
The Tools of Subsurface Analysis
Professor Chris Kendall
EWS 304
GEOL 553 Lecture 3; Subsurface Analysis

2. 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

3. Well Logs Versus Seismic
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

4. 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

5. 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

6. GEOL 553 Lecture 3; Subsurface Analysis
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

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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

10. GEOL 553 Lecture 3; Subsurface Analysis

11. 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

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13. GEOL 553 Lecture 3; Subsurface Analysis
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

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After Harris & Saller 1999

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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

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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

19. GEOL 553 Lecture 3; Subsurface Analysis
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

20. GEOL 553 Lecture 3; Subsurface Analysis

21. GEOL 553 Lecture 3; Subsurface Analysis

22. 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

23. GEOL 553 Lecture 3; Subsurface Analysis
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

24. GEOL 553 Lecture 3; Subsurface Analysis
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

25. GEOL 553 Lecture 3; Subsurface Analysis
Seismic Boundaries
Below Boundary - Toplap termination
GEOL 553 Lecture 3; Subsurface Analysis

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Seismic Boundaries
Below Boundary - Truncation of surface
GEOL 553 Lecture 3; Subsurface Analysis

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Seismic Boundaries
Channeled
Surface
– Below Boundary
GEOL 553 Lecture 3; Subsurface Analysis

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Seismic Boundaries
Over Boundary - Onlap onto surface
GEOL 553 Lecture 3; Subsurface Analysis

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Seismic Boundaries
Over Boundary- Downlap onto surface
GEOL 553 Lecture 3; Subsurface Analysis

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34. 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

35. 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

36. 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

37. GEOL 553 Lecture 3; Subsurface Analysis

38. 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

39. GEOL 553 Lecture 3; Subsurface Analysis

40. 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

41. GEOL 553 Lecture 3; Subsurface Analysis

42. 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

43. GEOL 553 Lecture 3; Subsurface Analysis

44. 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

45. GEOL 553 Lecture 3; Subsurface Analysis
Ebb Ooid Delta - UAE
GEOL 553 Lecture 3; Subsurface Analysis

46. Delta Mouth Bar - Kentucky
Note Incised Surface
GEOL 553 Lecture 3; Subsurface Analysis

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Channel – Gulf Coast
Note Incised Surface
GEOL 553 Lecture 3; Subsurface Analysis

48. Flood Deltas & Channels - Kty
GEOL 553 Lecture 3; Subsurface Analysis

49. Tidal Channels Khor al Bazam - UAE
GEOL 553 Lecture 3; Subsurface Analysis

50. Tidal, Storm or Tsunami Channel
Note Incised Surface
GEOL 553 Lecture 3; Subsurface Analysis

51. Tsunami Load & Drape - Kty
Note Uniform Thickness of Layer
GEOL 553 Lecture 3; Subsurface Analysis

52. Clastic Sequence Stratigraphic Hierarchies
GEOL 553 Lecture 3; Subsurface Analysis

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Channels & Shelves
Channel
Shelf
Both have unique processes & structures that can be used to identify their setting
GEOL 553 Lecture 3; Subsurface Analysis

54. 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

55. Sequence Stratigraphic Analysis
GEOL 553 Lecture 3; Subsurface Analysis

56. End of the Lecture
Can it be supper time?

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59. 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