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Topic. Planning Geochemical Evaluation of a Basin. Organic geochemistry in an exploration program. Specific applications depend on stage of exploration. Geochemistry in an exploration program. Combine geochemistry with geology and geophysics.

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  1. Topic Planning Geochemical Evaluation of a Basin

  2. Organic geochemistry in an exploration program Specific applications depend on stage of exploration

  3. Geochemistry in an exploration program Combine geochemistry with geology and geophysics FRONTIER AREA GENERAL PRINCIPLES DEVELOPING PLAY MATURE AREA DETAILED ANALYSIS

  4. Frontier area: before the first wildcat • Surface geology / seismic • Outcrop samples • Surface seeps • Surface microseeps “surface geochemistry” • Tentative thermal modeling

  5. Surface Geochemistry

  6. Outcrop Samples Tie surface units into the subsurface with seismic NEED TO BE AS FRESH AS POSSIBLE: use mines, roadcuts, etc. PROVIDES INFORMATION ON: organic matter content organic matter type maturity

  7. Van Krevelen diagrams for outcrop samples

  8. Developing play: limited subsurface data • Extending and refining quantitative modeling • Source rock richness and maturity • Oil characteristics – and inferred source rock lithology/environment • Correlation to give number of oil families and from this number of source rocks • Oil-versus-gas potential of the area

  9. Mature exploration area: abundant data • Refine maturity modeling to extend exploration to adjacent areas • Extend correlation studies • Improved definition of migration pathways • Define patterns of oil quality (e.g., biodegraded oils)

  10. Reservoirgeochemistry • Recognize reservoir compartments • Document compositional differences that lead to differences in physical properties which could affect flow models • Investigate tar layers that can influence water drive and water flooding

  11. How Do I Initiate and Complete a Geochemical Study? • Consult with a geochemist early to determine: objectives sampling strategy, analytical scheme • Initiate the project: formalize objectives, costs, and timing agree on expected final product • Supply carefully labeled samples, geology • Maintain communication during analysis • Integrate geochemistry and geology with geochemist for final interpretative report

  12. Data Quality Depends on CollectionProcedures and Sample Containers Sample Oil/Seep Source rock(General) Source rock(Outcrop) Comment Any clean, gas-tight container;avoid contact of sample with cap.Metal is best, glass is good if packed not to breakDo not use newspaper to wraprocks or pens to mark directlyon rocks. Avoid waxed cores! Sample unweathered rock; dig toexpose fresh surfaces at roadcuts,river banks, low-dip outcrops Ideal Container Clean metal vessel;gas-tight screw cap Cloth rock bagquality paper OK Cloth rock bag,quality paper OK

  13. Data Quality Depends on CollectionProcedures and Sample Containers Sample Source rock(cuttings) Reservoirrock (core) Gas Gas seep Comment Wash cuttings to remove drillingmud and contaminants Foil wrapped and sealed samplesare best. Avoid waxed cores! Sample at well head if possible Any gas-tight container. Samplesshould be shipped upside-downwith water/bacteriocide Ideal Container Cuttings envelopeor small vial Cloth rock bag,quality paper OK Pressure bomb Sampling bottle

  14. Sampling OILS Produced samples (e.g., DSTs) are best RFTs or SFTs are next best— often contaminated by diesel when oil-based mud is used Core or sidewall core extracts are next best— chose least flushed material by sampling core center Cuttings are the least desirable sample type— Poor vertical resolution — High surface to volume of cuttings causes hydrocarbon flushing by drilling fluid and contamination by drilling additives

  15. Sampling OILS (cont) Collect oil/condensates in glass bottles or metal cans NEVER use plastic bottles (e.g., Cloxox bottles, plastic soda bottles) NEVER use containers with plastic-lined tops Label samples with: date, field, well, depth, formation, section, township & range (or lat. And long.), and country or state Pack glass containers in absorbent material (e.g., Vermiculite)

  16. Sampling GAS/CONDENSATE Gases should be collected in steel cylinders or gas bags Cylinders must be ordered several weeks in advance Cylinders are assembled and evacuated, then shipped to the field location When condensate is collected from a separator, collect near the END of the production test

  17. Sampling Collect samples of organic well additives! — oil-based muds (diesel, pipe dope, etc) — lost circulation material (walnut hulls, fibres, plastics, etc) — gilsonite If samples of additives are collected, then even contaminated oil samples can often be made useful

  18. Classical Geochemistry Books: J. M. Hunt, 1979, Petroleum Geochemistry and Geology B.Tissot and D. H. Welte, 1984, Petroleum Formation and Occurrence D. W. Waples, 1985, Geochemistry in Petroleum Exploration K. E. Peters and J. M. Moldowan, 1993, The Biomarker Guide

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