Professor Chris Kendall 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 GEOL 553 Lecture 3; 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 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 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 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

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

GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; Subsurface Analysis 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

GEOL 553 Lecture 3; Subsurface Analysis

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

GEOL 553 Lecture 3; Subsurface Analysis

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

GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; Subsurface Analysis

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

GEOL 553 Lecture 3; Subsurface Analysis 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

GEOL 553 Lecture 3; Subsurface Analysis 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

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

GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; 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 Seismic GEOL 553 Lecture 3; Subsurface Analysis

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

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

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

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

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

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

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

GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; Subsurface Analysis

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 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 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

GEOL 553 Lecture 3; Subsurface Analysis

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

GEOL 553 Lecture 3; Subsurface Analysis

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

GEOL 553 Lecture 3; Subsurface Analysis

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

GEOL 553 Lecture 3; Subsurface Analysis

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

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

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

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

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

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

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

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

Clastic Sequence Stratigraphic Hierarchies GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; Subsurface Analysis 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 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 GEOL 553 Lecture 3; Subsurface Analysis

End of the Lecture Can it be supper time?

GEOL 553 Lecture 3; Subsurface Analysis

GEOL 553 Lecture 3; Subsurface Analysis

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