GEOL 553: Marine Sediments University of South Carolina Fall 2005

1. 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

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 • 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

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. 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

7. GEOL 553 Lecture 3; Subsurface Analysis

8. GEOL 553 Lecture 3; Subsurface Analysis

9. 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

12. GEOL 553 Lecture 3; Subsurface Analysis

13. 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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15. GEOL 553 Lecture 3; Subsurface Analysis

16. GEOL 553 Lecture 3; Subsurface Analysis After Harris & Saller 1999

17. 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

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

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

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

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

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

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

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

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

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

49. TidalChannelsKhor alBazam-UAE GEOL 553 Lecture 3; Subsurface Analysis

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