formation evaluation and well log correlation
DESCRIPTION
A qualitative and quantitative assessment of the reservoir using well logsTRANSCRIPT
Formation evaluation and well log correlationSWAPNIL PAL
IMT GEOLOGICAL TECHNOLOGY
INDIAN INSTITUTE OF TEC HNOLOGY R OORKEE
Overview Well log definition and its importance
Fundamentals of qualitative and quantitative log interpretation
Formation evaluation with well logs
Processing and interpretation of well log data
Conclusion
Well logThe continuous recording 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.
Basic Logs Tools and their Measurements
Gamma Ray log
Basic Logs Tools and their Measurements
Calliper log
Basic Logs Tools and their Measurements
Electrical log
Basic Logs Tools and their Measurements
Density log
Basic Logs Tools and their MeasurementsNeutron log
Petrophysical Interpretation
Qualitative assessment Quantitative assessment
Assessment of reservoir properties, fluid type form log pattern.
Numerical estimation of reservoir properties viz. % of oil, water etc.
Basic steps for quick look evaluation
ROCK
Reservoir
Non-Reservoir
Hydrocarbon bearing
Water bearing
Gas bearing
Oil bearing
Qualitative Interpretation
Identification of Reservoir or Non-reservoir
Low gamma ray(Reservoir rock)
Identification of hydrocarbon or water bearing zone
Qualitative Interpretation
Low gamma ray +High Resistivity value
Qualitative Interpretation
Low gamma ray +High Resistivity value +Large deviation in RHOB and NPHI value(cross-over region)
Identification of oil or gas bearing zone
Qualitative Interpretation
Gas bearing zone
Oil bearing zone
Water bearing zone
Quantitative Interpretation
Estimation of 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.
Quantitative InterpretationEstimation of porosity
Quantitative InterpretationEstimation of porosity
Depth (m) Vsh PHID PHIdc PHIN PHInceffective (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
Quantitative InterpretationEstimation of porosity
Depth (m) Vsh PHID PHIdc PHIN PHInceffective (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
Quantitative InterpretationEstimation of porosity
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
Quantitative Interpretation
Estimation of hydrocarbon saturationCan 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
Quantitative Interpretation
Archie’s equation
Quantitative InterpretationCalculation of formation water resistivity : RwUsing 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
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
Calculation of water saturation in oil and gas zones
1930 1940 1950 1960 1970 1980 19900
0.2
0.4
0.6
0.8
1
1.2
Depth (m)
Sw: w
ater
satu
ratio
n
Qualitative Interpretation
Gas bearing zone
Oil bearing zone
Water bearing zone
1930 1940 1950 1960 1970 1980 19900
0.2
0.4
0.6
0.8
1
1.2
Depth (m)
Sw: w
ater
sat
urati
on
Hurray!Oil found!!
V/sQuantitative Interpretation
Conclusion
Well logs contains key 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).
References
Archie II: Electrical conduction 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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