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Chemostratigraphy Concepts Carbonate Applications

Chemostratigraphy Concepts Carbonate Applications. Overview. What is Chemostratigraphy? Position within Reef System High Resolution Correlation Identification of Karst zones Hydrothermal Modification Oil Water Boundaries. Stratigraphy is the study of layered rocks

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Chemostratigraphy Concepts Carbonate Applications

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  1. Chemostratigraphy ConceptsCarbonate Applications

  2. Overview • What is Chemostratigraphy? • Position within Reef System • High Resolution Correlation • Identification of Karst zones • Hydrothermal Modification • Oil Water Boundaries

  3. Stratigraphy is the study of layered rocks Rock Based - Lithostratigraphy Fossil Based - Biostratigraphy Time Based - Chronostratigraphy Chemistry Based - Chemostratigraphy

  4. What is chemostratigraphy? A tool to sub-divide and correlate Chemostratigraphy utilises changes in bulk inorganic geochemical (elemental) data The mineralogy of sediments is highly variable and should be reflected through in the inorganic geochemistry; Source area composition Weathering or diagenesis Palaeo-environment

  5. Integrated Approach Chemostratigraphy is characterisation – NOT DATING Biostratigraphy provides stratigraphic calibration to enable the construction of a chemostratigraphic composite type section that can used to interpret the data from wells with limited stratigraphic penetration PLUS RETEST THE BIOSTRATIGRAPHY

  6. In all some 50 elements are analysed for which can yield information on; • Provenance changes • Climatic changes • Palaeo environment • Lithology What is chemostratigraphy? Chemostratigraphy can be regarded as an extension to the way you use Gamma data. Clay mineral identification Gamma data is essentially the expression of K, Th and U data. Lithological variations Provenance changes especially heavy minerals and feldspars Sandstone Mg = Chlorite K = Illite Shale Zr = zirconCr = Cr spinelNa = Plagioclase feldspar Correlationpurposes Palaeo environmental reconstruction Redox conditions can be identified by elements such as Mo, As and Zn which have an affinity to organic material What more information could be gained if more elements analysed for?

  7. Chemostratigraphic rationale 3c 3b 3 3a 2 2 1c 1b 1 1a Package level = broadest definable geochemical grouping Unit level = definable geochemical grouping within each package

  8. Lithology Selection

  9. Analytical Techniques Inductively coupled plasma spectrometry Remains the most effective all round tool for analysis, but in recent years several other viable options have appeared X-Ray Fluorescence These instruments are now capable of producing high quality data comparable to ICP, but with sample quality limitations Bench-top X-Ray Fluorescence Small compact instruments that are now capable of producing good data in remote locations Laser Induced Breakdown spectroscopy Small compact instruments that are now capable of producing good data in remote locations

  10. Areas of Application Chemostrat Office and Laboratory Facilities Areas of Experience

  11. Analysis of Reef Systems

  12. Reef Cross Section

  13. Facies Differentiation

  14. Conclusion • The position of a well within a reef system can be determined from simple elemental proportions • The elemental contents provided can be independent of lithology

  15. Chemostratigraphic correlation:Emborê Formation

  16. Chemostratigraphic Correlation: – Emborê Fm.

  17. Chemostratigraphic correlation:Emborê Formation (Packages 1 & 2 Units)

  18. Lithostratigraphic correlation

  19. Chemostratigraphic correlation

  20. Conclusion • Chemostratigraphy can be used to determine package level correlations which can be confirmed by statistical analysis • Using a range of elemental proportions a high resolution unit level correlation can be provided in what appear to be homogeneous limestone facies • Compared with lithostratigraphic correlation chemostratigraphic correlation can provide improved resolution

  21. Karst Zones

  22. Karst Zones

  23. Conclusion • Chemostratigraphy can be used to identify zones aerial and sub-aerial exposure events • Exposure and sub-aerial events can be correlated

  24. Hydrothermal Zones

  25. Sweet Zone Identification

  26. Conclusion • Hydrothermal zones can be identified and characterised • By using a comparison of different elemental proportions it is possible to identify ‘sweet zones’

  27. Oil Distribution

  28. Conclusion • Elements associated with oil can be used to model oil distribution within carbonate systems • Elements associated with formation waters can be used in association with organic indicators to model position of oil water boundaries within carbonate systems

  29. Questions?

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