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Formation evaluation and well log correlation
This document provides an overview of well log formation evaluation and interpretation. It discusses the basic well log tools used to measure parameters like gamma ray, resistivity, density, and neutron porosity. It describes qualitative log interpretation to identify reservoir zones, hydrocarbon-bearing zones, and fluid types. The document also covers quantitative interpretation, including calculating porosity, water saturation, and estimating hydrocarbon reserves. In conclusion, well logs provide key information for establishing the existence of producible oil and gas reservoirs, including reservoir type, thickness, porosity, permeability, and fluid saturation.
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Formation evaluation and well log correlation
- 1. Formation evaluation and welllog correlation SWAPNIL PAL IMT GEOLOGICAL TECHNOLOGY INDIAN INSTITUTE OF TECHNOLOGY ROORKEE
- 2. Overview Well log definitionand its importance Fundamentals of qualitative and quantitative log interpretation Formation evaluation with well logs Processing and interpretation of well log data Conclusion
- 3. Well log The continuousrecording of a geophysical parameter along a borehole produces a geophysical well log. The value of the measurement is plotted continuously against depth in the well.
- 4. Basic Logs Toolsand their Measurements Gamma Ray log
- 5. Basic Logs Toolsand their Measurements Calliper log
- 6. Basic Logs Toolsand their Measurements Electrical log
- 7. Basic Logs Toolsand their Measurements Density log
- 8. Basic Logs Toolsand their Measurements Neutron log
- 9. Petrophysical Interpretation Qualitative assessmentQuantitative assessment Assessment of reservoir properties, fluid type form log pattern. Numerical estimation of reservoir properties viz. % of oil, water etc.
- 10. Basic steps forquick look evaluation ROCK Reservoir Non-Reservoir Hydrocarbon bearing Water bearing Gas bearing Oil bearing
- 11. Qualitative Interpretation Identification ofReservoir or Non-reservoir Low gamma ray (Reservoir rock)
- 12. Identification of hydrocarbonor water bearing zone Qualitative Interpretation Low gamma ray + High Resistivity value
- 13. Qualitative Interpretation Low gammaray + High Resistivity value + Large deviation in RHOB and NPHI value (cross-over region) Identification of oil or gas bearing zone
- 14. Qualitative Interpretation Gas bearingzone Oil bearing zone Water bearing zone
- 15. Quantitative Interpretation Estimationof effective porosity & permeability. Estimation of volume of clay fraction. Estimation of hydrocarbon saturation. Determination of the depth and thickness of net pay. Estimation of reserves of hydrocarbon.
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- 17. Quantitative Interpretation Estimation ofporosity Depth (m) Vsh PHID PHIdc PHIN PHInc effective (Gas) 1940 0.710526 0.278788 0.106539 0.46 0.175789 0.145349 1945 0.078947 0.418182 0.399043 0.09 0.058421 0.285174 1948 0.052632 0.381818 0.369059 0.07 0.048947 0.263249 1950 0.039474 0.424242 0.414673 0.06 0.044211 0.29488 1953 0.039474 0.484848 0.475279 0.14 0.124211 0.34736 1957 0.697368 0.327273 0.158214 0.33 0.051053 0.117554 1958 0.644737 0.266667 0.110367 0.41 0.152105 0.132885 gas bearing zone
- 18. Quantitative Interpretation Estimation ofporosity Depth (m) Vsh PHID PHIdc PHIN PHInc effective (Gas) 1970 0.657895 0.236364 0.076874 0.36 0.096842 0.086858 1972 0.644737 0.218182 0.061882 0.325 0.067105 0.064494 1974 0.118421 0.272727 0.244019 0.19 0.142632 0.193325 1976 0.460526 0.272727 0.161085 0.34 0.155789 0.158437 1978 0.276316 0.254545 0.18756 0.22 0.109474 0.148517 1980 0.434211 0.272727 0.167464 0.275 0.101316 0.13439 1982 0.263158 0.284848 0.221053 0.24 0.134737 0.177895 1984 0.723684 0.254545 0.079107 0.43 0.140526 0.109817 oil bearing zone
- 19. Quantitative Interpretation Estimation ofporosity Depth (m) Vsh PHID PHIdc 2025 0.236842 0.278788 0.212759 2028 0.565789 0.230303 0.1 2029 0.328947 0.212121 0.142344 2030 0.276316 0.260606 0.188596 2031 0.342105 0.242424 0.15949 2034 0.394737 0.278788 0.16874 2035 0.223684 0.260606 0.202313 2036 0.223684 0.260606 0.202313 2037 0.197368 0.236364 0.189713 water bearing zone
- 20. Quantitative Interpretation Estimation ofhydrocarbon saturation Can not be measured directly but inferred from determination of WATER SATURATION (Sw) from RESISTIVITY and POROSITY logs. • Sw – Fraction of pore space occupied by water. • Sh – Fraction of pore space occupied by hydrocarbon. Sh + Sw = 1 Oil Water
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- 22. Quantitative Interpretation Calculation offormation water resistivity : Rw Using Inverse Archie’s equation Rt 0.95 0.7 0.1 0.8 0.9 0.7 0.7 0.7 0.85 Rw 0.073837 0.037128 0.0045 0.054332 0.052893 0.054406 0.047541 0.047541 0.047488 Depth 2025 2028 2029 2030 2031 2034 2035 2036 2037 Water bearing zone Rw= 0.05, this is used in Archie’s equation to calculate water saturation in oil and gas bearing zone
- 23. Quantitative Interpretation Depth 1940 1945 1948 1950 1953 1957 1958 1970 1972 1974 1976 1978 1980 1982 1984 PHId 0.278788 0.418182 0.381818 0.424242 0.484848 0.327273 0.266667 0.236364 0.212121 0.272727 0.272727 0.254545 0.272727 0.290909 0.254545 Rt 0.65 15 35 48 33 0.9 0.85 1 1.5 2 4 2.9 3 1.2 0.8 Sw (Archie) 0.994843 0.138062 0.098991 0.076076 0.080283 0.720201 0.909509 0.946029 0.860707 0.579751 0.409946 0.515847 0.473365 0.701677 0.982143 Calculationof water saturation in oil and gas zones 0 0.2 0.4 0.6 0.8 1 1.2 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 Sw:watersaturation Depth (m)
- 24. Qualitative Interpretation Gas bearingzone Oil bearing zone Water bearing zone 0 0.2 0.4 0.6 0.8 1 1.2 1930 1940 1950 1960 1970 1980 1990 Sw:watersaturation Depth (m) Hurray! Oil found!! V/s Quantitative Interpretation
- 25. Conclusion Well logs containskey information about the formation drilled in different petro-physical measurements. i.e. Prospective zones of hydrocarbon. Reservoir type and thickness. Estimation of Porosity, permeability. Fluid type present in the pores and saturation level. To economically establish the existence of producible hydrocarbon reservoirs (oil & gas).
- 26. References Archie II: Electricalconduction in hydrocarbon bearing zone. (n.d.). In Rock Physics (Vol. 36). Archie III: Electrical conduction in shaly sand. (n.d.). In Rock Physics (Vol. 1). Archie's law: Electrical conduction in clean, water bearing rock. (n.d.). In Rock physics/History (Vol. 36). Halliburton. (n.d.). Log Interpretation Charts. M H Rider. (1991). The Geological Interpretation of well logs. Glasgow: Whittes Publishing. (1989). Open hole well logging Interpretation. Texas: Schlumberger Wireline & Testing. Serra, O. (1984). Fundamentals of well log interpretation. Amsterdam: Elsevier.
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