Source Rock.pdf

Chapter 7: Source Rock Agenda 1. Source Rock 2. Method to evaluate source rock Criteria to produce good source rock Carbon cycle Fate of OM in Oceans Organic Matter (OM) Requirements for High Organic Productivity Preservation of OM Evolution of the Source Rock Source Rock Evaluatio...

Chapter 7: Source Rock Agenda 1. Source Rock 2. Method to evaluate source rock Criteria to produce good source rock Carbon cycle Fate of OM in Oceans Organic Matter (OM) Requirements for High Organic Productivity Preservation of OM Evolution of the Source Rock Source Rock Evaluation Total Organic Carbon (TOC) Type of OM Microscopic Method Element C/N ratio (marine vs terrestrial) C/N < 8 – Marine C/N: 8-15 Mixed C/N: > 20 Terrestrial Type of OM : C-isotopes vs C/N ratio Elemental Analysis Van Krevelan diagrams based on elemental (H/C and O/C) ratio Algal Kerogen (Mainly aliphatic chains) Liptinic Kerogen (More aromatic naphthenic ring) Humic or vitrinite (terrestrial plant origin mostly aromatic rings) Increasing burial Maturity of Kerogen in source rocks Methods to determine the maturity of Kerogen Chemical methods: 1. Elemental (C/H and C/O) ratios 2. Pyrolysis: Rock – Eval analysis Mineralogical methods: 1. Percentage of illite in illite-smectite mixed-layer clay mineral Biological methods: 1. Vitrinite reflectance Chemical method - elemental H/C and O/C Chemical method - elemental H/C and O/C Chemical methods – Pyrolysis: Rock-Eval analysis Device Pyrolysis Pyrolysis Geochemical Log Mineralogical Methods - % illite in illite/smectite clay Biological Methods Biological Methods Biological Methods Biological Methods Biological Methods Take home points for Source Rocks  Required: - High organic productivity - Preservation (anoxic conditions)  Chain of thermal maturation : Organic Matter  Kerogen types: I algal ---Oil, II sapropelic ---Oil + gas, III humic ---gas  Immature, mature, overmature condition determine remaining generation potential  Pyrolysis and vitrinite reflectance can be used to determined source rock maturity