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Questions and Answers
What is the primary difference between total porosity and effective porosity?
Which type of log measures hydrogen density to infer porosity?
Which resistivity logging tool measures resistivity at a distance from the wellbore?
What is the formula for calculating total porosity using formation density?
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Which method of resistivity modeling simplifies the formation into layers or blocks?
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What is the role of the cementation exponent (m) in fluid saturation calculations?
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Which equation is used to calculate fluid saturation using resistivity logs?
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What is one of the primary applications of resistivity modeling in reservoir characterization?
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For effective porosity calculation, which variable is taken into account besides total porosity?
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How do density logs contribute to porosity measurement?
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Study Notes
Numerical Well Logging
Porosity Analysis
- Porosity: measure of the percentage of void space in a rock formation
-
Types of Porosity:
- Total porosity: sum of all pore spaces
- Effective porosity: connected pore spaces that allow fluid flow
-
Porosity measurement methods:
- Neutron logs: measure hydrogen density, related to porosity
- Density logs: measure formation density, related to porosity
- Sonic logs: measure travel time of sound waves, related to porosity
-
Porosity calculation:
- Total porosity:
φ = (ρ_ma - ρ_b) / (ρ_ma - ρ_f) - Effective porosity:
φ_e = φ \* (1 - Sw)
- Total porosity:
Resistivity Modeling
- Resistivity: measure of a formation's ability to resist electric current flow
-
Resistivity logging tools:
- Laterologs: measure resistivity of the formation at a distance from the wellbore
- Induction logs: measure resistivity of the formation around the wellbore
-
Resistivity modeling methods:
- Analytic models: simplify the formation into layers or blocks
- Numerical models: discretize the formation into a grid or mesh
-
Resistivity modeling applications:
- Identify hydrocarbon-bearing zones
- Estimate fluid saturations
- Monitor reservoir performance
Fluid Saturation Calculations
- Fluid saturations: percentage of each fluid type (water, oil, gas) in the pore space
-
Fluid saturation calculation methods:
- Archie's equation:
Sw = (a \* R_w) / (R_t \* φ^m) - Simandoux's equation:
Sw = (R_t / R_w)^(1/m)
- Archie's equation:
-
Fluid saturation calculation inputs:
- Resistivity logs (R_t)
- Porosity logs (φ)
- Water resistivity (R_w)
- Cementation exponent (m)
-
Fluid saturation applications:
- Identify hydrocarbon-bearing zones
- Estimate hydrocarbon in place
- Monitor reservoir performance
Numerical Well Logging
Porosity Analysis
- Porosity: a measure of the percentage of void space in a rock formation, ranging from 0 (no voids) to 1 (entirely void)
-
Types of Porosity:
- Total Porosity: the sum of all pore spaces in a rock
- Effective Porosity: connected pore spaces that allow fluid flow
-
Porosity Measurement Methods:
- Neutron Logs: measure hydrogen density, which is related to porosity
- Density Logs: measure formation density, which is related to porosity
- Sonic Logs: measure travel time of sound waves, which is related to porosity
-
Porosity Calculation:
-
Total Porosity:
φ = (ρ_ma - ρ_b) / (ρ_ma - ρ_f) -
Effective Porosity:
φ_e = φ \* (1 - Sw)
-
Total Porosity:
Resistivity Modeling
- Resistivity: a measure of a formation's ability to resist electric current flow
-
Resistivity Logging Tools:
- Laterologs: measure resistivity of the formation at a distance from the wellbore
- Induction Logs: measure resistivity of the formation around the wellbore
-
Resistivity Modeling Methods:
- Analytic Models: simplify the formation into layers or blocks
- Numerical Models: discretize the formation into a grid or mesh
-
Resistivity Modeling Applications:
- Identify Hydrocarbon-Bearing Zones
- Estimate Fluid Saturations
- Monitor Reservoir Performance
Fluid Saturation Calculations
- Fluid Saturations: the percentage of each fluid type (water, oil, gas) in the pore space
-
Fluid Saturation Calculation Methods:
-
Archie's Equation:
Sw = (a \* R_w) / (R_t \* φ^m) -
Simandoux's Equation:
Sw = (R_t / R_w)^(1/m)
-
Archie's Equation:
-
Fluid Saturation Calculation Inputs:
- Resistivity Logs (R_t)
- Porosity Logs (φ)
- Water Resistivity (R_w)
- Cementation Exponent (m)
-
Fluid Saturation Applications:
- Identify Hydrocarbon-Bearing Zones
- Estimate Hydrocarbon in Place
- Monitor Reservoir Performance
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Description
Test your knowledge of porosity in well logging, including types of porosity and measurement methods. Learn about total and effective porosity, and how neutron, density, and sonic logs are used to measure porosity.
