7. Lithology Interpretation from Logs.pptx

GEOPYSICS

1. Lithology from Basic log

2. Lithology Gamma Ray, Spontaneous Potential, PEF Porosity Sonic, Density, Neutron, NMR Permeability Micro Resistivity, Sonic, NMR Hydrocarbon Saturation Resistivity Hydrocarbon Type Density-Neutron, NMR Objectives of Petrophysics Why We Log?

3. Well Logging

4. Lithology Interpretation from Basic Logs

5. In gauge Key seat Wash out Breakout Different types of boreholes shapes

6. SP Log Interpretation

7. Logs: Gamma Ray The  SGR (Sum GR)  records the total gamma ray count from all sources, while the  CGR (Computed GR)  results from the subtraction of the uranium contribution from the  SGR . Because the  CGR  is the summation of thorium and potassium sources, this curve is an improved log to estimate clay content, free of perturbations by uranium

8. Shale evaluation Sand Line 200 API units Shale Line ~50% shale line Depth control correlation form one run to another Correlation More sand Less Sand Gamma Log Application  

9. Lithology Estimation from Gamma General Gamma Ray Log Responses to Lithology Lithology API Integrate with other logs *Sandstone <30 Neutron-density, resistively, sonic, PEF Limestone <20 Neutron-density, resistively, sonic, PEF Dolomite <30 Neutron-density, resistively, sonic, PEF Shale 80-300 Neutron-density, resistively, sonic, PEF Coal <20 Neutron-density, resistively, sonic, PEF Salt <10 Neutron-density, resistively, sonic, PEF Anhydrite <10 Neutron-density, resistively, sonic, PEF *High Gamma Sandstones occur due to high mica, feldspar, or heavy radioactive minerals such zircon and apatite etc – Need NGT to resolve

10. Depositional Environment

11. Depositional Environment

12. Logs: Resistivity Presence of clays reduces the Resistivity values of Sandstone Response of deep resistivity on some minerals and typical distinctive lithologies

13. Logs: Sonic Compaction with depth

14. Logs: Neutron-Density

15. PEF Uses MATRIX IDENTIFICATION WITH THE Pe Limestone Pe = 5- 6 sandstone Pe = 3 (higher than text-book value) Normally PEF is plotted with the density curves

16. Logs: Photo-Electric Factor MATRIX IDENTIFICATION WITH THE Pe

17. Lithology identification From Gr, N-D

18. Formation Pressure on Fluid contact

19. Volume of shale (Vsh) from Gamma log Porosity (Phit) from Density log where ρ ma =2.65 gm/cc, ρ f =1 gm/cc Water saturation (Sw) using Archie Equation Possible fluid contacts from logs or pressure Petrophysical zone average reservoir/pay properties Quick-Look Interpretation Workflow Sw n = (1/ phit m )x( Rw /Rt) where m=1.8, n=1.8 & Rw =0.30 ohmm @ FT