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| | part = Critical elements of the petroleum system | | | part = Critical elements of the petroleum system |
| | chapter = Sedimentary basin analysis | | | chapter = Sedimentary basin analysis |
− | | frompg = 4-1 | + | | frompg = 4-40 |
− | | topg = 4-123 | + | | topg = 4-44 |
| | author = John M. Armentrout | | | author = John M. Armentrout |
| | link = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm | | | link = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm |
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| ==Building regional log cross sections== | | ==Building regional log cross sections== |
− | Regional stratigraphic well-log [[cross section]]s form the foundation for many basin studies. They give a regional view of basin stratigraphy and can be integrated with seismic and biostratigraphic data. The table below outlines the steps for building regional well-log cross sections. | + | Regional stratigraphic well-log [[cross section]]s form the foundation for many basin studies. They give a regional view of basin stratigraphy and can be integrated with seismic and biostratigraphic data. The list below outlines the steps for building regional well-log cross sections. |
| | | |
− | {| class = "wikitable"
| + | # Build a grid of well-log sections that crosses the entire basin, either along depositional [[dip]] or depositional strike. Use as many wells as practical. Where available, add measured sections and [[core description]]s to the grid. |
− | |-
| + | # Correlate cross sections. Look for [[Unconformity|unconformities]] and flooding surfaces. |
− | ! Step
| + | # Tie the correlations from depositional-dip sections to depositional-strike sections. |
− | ! Action
| + | # Confirm correlations on seismic reflection profiles. |
− | |-
| |
− | | 1
| |
− | | Build a grid of well-log sections that crosses the entire basin, either along depositional dip or depositional strike. Use as many wells as practical. Where available, add measured sections and [[core description]]s to the grid.
| |
− | |-
| |
− | | 2
| |
− | | Correlate cross sections. Look for [[Unconformity|unconformities]] and flooding surfaces.
| |
− | |-
| |
− | | 3
| |
− | | Tie the correlations from depositional-dip sections to depositional-strike sections.
| |
− | |-
| |
− | | 4
| |
− | | Confirm correlations on seismic reflection profiles.
| |
− | |}
| |
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| ==Biostratigraphic patterns== | | ==Biostratigraphic patterns== |
− | Using chronostratigraphically significant bioevents as defined by microfossil extinction events and abundance patterns, local cycles of transgression and [[regression]] can be correlated from well to well, providing a high-resolution calibration of depositional cyclicity. Patterns of relative dilution vs. concentration of fossils that correlate over a significant geographic area, such as a large portion of a basin margin, can be interpreted as reflecting cycles of regional transgression and regression rather than local lateral shifting of sediment input points. | + | Using chronostratigraphically significant bioevents as defined by microfossil extinction events and abundance patterns, local cycles of transgression and [[regression]] can be correlated from well to well, providing a high-resolution calibration of depositional cyclicity. Patterns of relative dilution vs. concentration of fossils that correlate over a significant geographic area, such as a large portion of a basin margin, can be interpreted as reflecting cycles of regional transgression and regression rather than local [[lateral]] shifting of sediment input points. |
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− | Stratigraphic intervals rich in calcareous nannoplankton and foraminiferal fossils and having maximum gamma-ray values are interpreted to correlate with condensed depositional intervals deposited during relative sediment starvation related to transgression.<ref name=ch04r59>Loutit, T., S., Hardenbol, J., Vail, P., R., Baum, G., R., 1988, Condensed sections: the key to age determination and correlation of continental margin sequences: SEPM Special Publication 42, p. 183–213.</ref> Intervals devoid of fossils or having low abundance values, often associated with sandy lithofacies, can be interpreted as deposited during relative high rates of accumulation related to [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]] of the sediment supply into the area of the well, marking a phase of regression. Biofacies are interpreted using benthic foraminiferal assemblages indicative of water mass conditions.<ref name=ch04r97>Tipsword, H., L., J., Setzer, F., M., Smith, F., L. Jr., 1966, Interpretation of depositional environment in Gulf Coast exploration from paleoecology and related stratigraphy: Gulf Coast Assoc. of Geological Societies Transactions, vol. 16, p. 119–130.</ref><ref name=ch04r28>Culver, S., J., 1988, New foraminiferal depth zonation of the northwestern Gulf of Mexico: Palaios, vol. 3, p. 69–85., 10., 2307/3514545</ref><ref name=ch04r7>Armentrout, J., M., 1991, Paleontological constraints on depositional [[modeling]]: examples of integration of biostratigraphy and seismic stratigraphy, Pliocene–Pleistocene, Gulf of Mexico, in Weimer, P., Link, M., H., eds., Seismic Facies and Sedimentary Processes of Submarine Fans and Turbidite Systems: New York, Springer-Verlag, p. 137–170.</ref> | + | Stratigraphic intervals rich in calcareous nannoplankton and foraminiferal fossils and having maximum gamma-ray values are interpreted to correlate with condensed depositional intervals deposited during relative sediment starvation related to transgression.<ref name=ch04r59>Loutit, T., S., Hardenbol, J., Vail, P., R., Baum, G., R., 1988, Condensed sections: the key to age determination and correlation of continental margin sequences: SEPM Special Publication 42, p. 183–213.</ref> Intervals devoid of fossils or having low abundance values, often associated with sandy [[lithofacies]], can be interpreted as deposited during relative high rates of accumulation related to [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]] of the sediment supply into the area of the well, marking a phase of regression. Biofacies are interpreted using benthic foraminiferal assemblages indicative of water mass conditions.<ref name=ch04r97>Tipsword, H., L., J., Setzer, F., M., Smith, F., L. Jr., 1966, Interpretation of depositional environment in Gulf Coast exploration from paleoecology and related stratigraphy: Gulf Coast Assoc. of Geological Societies Transactions, vol. 16, p. 119–130.</ref><ref name=ch04r28>Culver, S., J., 1988, New foraminiferal depth zonation of the northwestern Gulf of Mexico: Palaios, vol. 3, p. 69–85., 10., 2307/3514545</ref><ref name=ch04r7>Armentrout, J., M., 1991, Paleontological constraints on depositional [[modeling]]: examples of integration of biostratigraphy and seismic stratigraphy, Pliocene–Pleistocene, Gulf of Mexico, in Weimer, P., Link, M., H., eds., Seismic Facies and Sedimentary Processes of Submarine Fans and Turbidite Systems: New York, Springer-Verlag, p. 137–170.</ref> |
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| ==GOM basin example== | | ==GOM basin example== |
| In the GOM basin, variations in well-log response and [[Fossil assemblage|biofacies]] distribution are analyzed for recognition of stacked depositional sequences. The [[Basic open hole tools#Gamma ray|gamma-ray]] log display provides a measure of sediment type, with curve deflections to the left suggesting increased sand content while high values to the right indicate increases in clay content. Use of multiple logs, especially [[Basic open hole tools#Spontaneous potential|spontaneous potential]], [[Basic open hole tools#Resistivity|resistivity]], density, and velocity logs calibrated by well-cutting descriptions and formation microscanner displays, provides a data set for reliable rock type identification. The figure below illustrates an interpretation template for log motif analysis. | | In the GOM basin, variations in well-log response and [[Fossil assemblage|biofacies]] distribution are analyzed for recognition of stacked depositional sequences. The [[Basic open hole tools#Gamma ray|gamma-ray]] log display provides a measure of sediment type, with curve deflections to the left suggesting increased sand content while high values to the right indicate increases in clay content. Use of multiple logs, especially [[Basic open hole tools#Spontaneous potential|spontaneous potential]], [[Basic open hole tools#Resistivity|resistivity]], density, and velocity logs calibrated by well-cutting descriptions and formation microscanner displays, provides a data set for reliable rock type identification. The figure below illustrates an interpretation template for log motif analysis. |
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− | Patterns of forestepping vs. backstepping log-motif funnels can define transgressive vs. [[regressive]] depositional trends and candidate systems tracts and sequences. Vail and Wornardt<ref name=ch04r101>Vail, P., R., Wornardt, W., W., 1990, Well log seismic stratigraphy: a new tool for exploration in the '90s: Proceedings, Gulf Coast Section SEPM 11th Annual Research conference, p. 379–388.</ref> and Armentrout et al.<ref name=ch04r8>Armentrout, J. M., S. J. Malacek, L. B. Fearn, C. E. Sheppard, P. H. Naylor, A. W. Miles, R. J. Desmarais, and R. E. Dunay, 1993, Log-motive analysis of Paleogene depositional systems tracts, central and northern North Sea: Defined by sequence stratigraphic analysis ''in'' J. R. Parker, ed., Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference, The Geological Society of London, p. 45-57.</ref> detail the process. | + | Patterns of forestepping vs. backstepping log-motif funnels can define transgressive vs. [[Regression|regressive]] depositional trends and candidate systems tracts and sequences. Vail and Wornardt<ref name=ch04r101>Vail, P., R., Wornardt, W., W., 1990, Well log seismic stratigraphy: a new tool for exploration in the '90s: Proceedings, Gulf Coast Section SEPM 11th Annual Research conference, p. 379–388.</ref> and Armentrout et al.<ref name=ch04r8>Armentrout, J. M., S. J. Malacek, L. B. Fearn, C. E. Sheppard, P. H. Naylor, A. W. Miles, R. J. Desmarais, and R. E. Dunay, 1993, Log-motive analysis of Paleogene depositional systems tracts, central and northern North Sea: Defined by sequence stratigraphic analysis ''in'' J. R. Parker, ed., Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference, The Geological Society of London, p. 45-57.</ref> detail the process. |
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| ==GOM basin example chart== | | ==GOM basin example chart== |
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| </gallery> | | </gallery> |
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− | The histogram patterns of foraminiferal and calcareous nannoplankton abundance for the South Galveston Mobil A-158 #3 well are shown in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]]. The histogram is based on a detailed checklist of the relative abundance of each species of fossil in each well-cutting sample.<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref> Display of this data in two-way time facilitates integration with seismic reflection profiles using the [[synthetic seismogram]] to match the well data with the seismic reflection profile at the well site. Patterns of shallow vs. deep [[Fossil assemblage|biofacies]] and fossil abundance (i.e., concentration vs. dilution) can be correlated with [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]] of sandstone vs. mudstone interpreted from wireline log patterns. Bioevents (abbreviated acronyms such as 2B and SG) and faunal discontinuity events (abbreviated FDA-3 and FDA-4) provide correlation horizons between which the abundance patterns provide additional events for correlation.<ref name=ch04r7 /> | + | The histogram patterns of foraminiferal and calcareous nannoplankton abundance for the South Galveston Mobil A-158 #3 well are shown in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]]. The histogram is based on a detailed checklist of the relative abundance of each species of fossil in each well-cutting sample.<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref> Display of this data in two-way time facilitates integration with seismic reflection profiles using the [[synthetic seismogram]] to match the well data with the seismic reflection profile at the well site. Patterns of shallow vs. deep [[Fossil assemblage|biofacies]] and fossil abundance (i.e., concentration vs. dilution) can be correlated with [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]] of sandstone vs. [[mudstone]] interpreted from wireline log patterns. Bioevents (abbreviated acronyms such as 2B and SG) and faunal discontinuity events (abbreviated FDA-3 and FDA-4) provide correlation horizons between which the abundance patterns provide additional events for correlation.<ref name=ch04r7 /> |
| | | |
| In the histogram in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]] (see [[:file:sedimentary-basin-analysis_fig4-17.png|Figure 1]] for well location), the foraminiferal abundance scale is 0-1000 specimens and the nannoplankton abundance scale is 0-800 specimens. Biofacies include inner neritic (IN, 0-50 m), middle neritic (MN, 50-100 m), outer neritic (ON, 100-200 m), upper bathyal (UPPB, 200-500 m), middle bathyal (MDLB, 500-1000 m), and lower bathyal (LOWB, 1000–2000 m). This figure is the leftmost (southern) well panel in [[:file:sedimentary-basin-analysis_fig4-24.png|Figure 4]]. The wireline log (gamma ray) motif patterns ([[:file:sedimentary-basin-analysis_fig4-22.png|Figure 2]]), biostratigraphic abundance events, and extinction datums provide correlation events. | | In the histogram in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]] (see [[:file:sedimentary-basin-analysis_fig4-17.png|Figure 1]] for well location), the foraminiferal abundance scale is 0-1000 specimens and the nannoplankton abundance scale is 0-800 specimens. Biofacies include inner neritic (IN, 0-50 m), middle neritic (MN, 50-100 m), outer neritic (ON, 100-200 m), upper bathyal (UPPB, 200-500 m), middle bathyal (MDLB, 500-1000 m), and lower bathyal (LOWB, 1000–2000 m). This figure is the leftmost (southern) well panel in [[:file:sedimentary-basin-analysis_fig4-24.png|Figure 4]]. The wireline log (gamma ray) motif patterns ([[:file:sedimentary-basin-analysis_fig4-22.png|Figure 2]]), biostratigraphic abundance events, and extinction datums provide correlation events. |
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| ==See also== | | ==See also== |
− | * [[Depositional sequence]] | + | * [[East Breaks depositional sequence]] |
| * [[Definitions of depositional system elements]] | | * [[Definitions of depositional system elements]] |
| * [[Identifying depositional sequences]] | | * [[Identifying depositional sequences]] |
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| [[Category:Critical elements of the petroleum system]] | | [[Category:Critical elements of the petroleum system]] |
| [[Category:Sedimentary basin analysis]] | | [[Category:Sedimentary basin analysis]] |
| + | [[Category:Treatise Handbook 3]] |