Changes

==Interpret the Lithology==

==Interpret the Lithology==

[[File:Well_Log_Analysis_Fig-3.png|thumb|300px|Figure 3-The use of gamma ray log to determine the lithology.<ref>Railsback (2011). Characteristics of wireline well logs in the petroleum industry.</ref>]]

[[File:Well_Log_Analysis_Fig-3.png|thumb|300px|Figure 3-The use of gamma ray log to determine the lithology.<ref>Railsback, 2011, Characteristics of wireline well logs in the petroleum industry.</ref>]]

The user will be able to interpret the lithology by using several logs, there are gamma ray, spontaneous potential, resistivity, and [[density log]]. Basically, a formation with high gamma ray reading indicates that it is a shaly or shale, when the low gamma ray reading indicates a clean formation (sand, carbonate, [[evaporite]], etc.), lithology interpretation is very important in reservoir characterization because, if the lithology interpretation is already wrong, the other steps such as porosity and water saturation calculation will be a total mess.

The user will be able to interpret the lithology by using several logs, there are gamma ray, spontaneous potential, resistivity, and [[density log]]. Basically, a formation with high gamma ray reading indicates that it is a shaly or shale, when the low gamma ray reading indicates a clean formation (sand, carbonate, [[evaporite]], etc.), lithology interpretation is very important in reservoir characterization because, if the lithology interpretation is already wrong, the other steps such as porosity and water saturation calculation will be a total mess.

| [[Dolomite]] || 2.877 || Methane || 0.423

| [[Dolomite]] || 2.877 || Methane || 0.423

|-

|-

| Anhydrite || 2.960 || Oil || 0.8

| [[Anhydrite]] || 2.960 || Oil || 0.8

|-

|-

| Salt || 2.040 || ||

| Salt || 2.040 || ||

==Calculate the Water Saturation==

==Calculate the Water Saturation==

There are so many methods to calculate water saturation, the user may use Archie’s,<ref>Archie, G. E. (1950). Introduction to petrophysics of reservoir rocks. AAPG Bulletin, 34(5), 943-961.</ref> Simandoux’s (1963), etc. which will use different formula for every one of them, but in this article, the author will use Simandoux’s (1963) method, to calculate the water saturation by using this method, the user will need to use the following formula:

There are so many methods to calculate water saturation, the user may use Archie’s,<ref>Archie, G. E., 1950, Introduction to petrophysics of reservoir rocks: AAPG Bulletin, v. 34, no. 5, p. 943-961.</ref> Simandoux’s (1963), etc. which will use different formula for every one of them, but in this article, the author will use Simandoux’s (1963) method, to calculate the water saturation by using this method, the user will need to use the following formula:

:<math>\frac{1}{Rt} = \frac{Sw^2}{F \times Rw} + \frac{Vsh \times Sw}{Rsh}</math>

:<math>\frac{1}{Rt} = \frac{Sw^2}{F \times Rw} + \frac{Vsh \times Sw}{Rsh}</math>

{| class = wikitable

{| class = wikitable

|-

|-

|+ Table 3-Tortuosity factor (a) and cementation exponent (m) reference table.<ref name=Asquith />

|+ Table 3. Tortuosity factor (a) and cementation exponent (m) reference table.<ref name=Asquith />

|-

|-

! Lithology || a (tortuosity factor) || m (cementation exponent)

! Lithology || a (tortuosity factor) || m (cementation exponent)

{| class="wikitable"

{| class="wikitable"

|-

|-

|+ Table 4-Matrix and fluid transit time reference table.<ref>Schlumberger Limited. (1984). Schlumberger log interpretation charts. Schlumberger.</ref>

|+ Table 4. Matrix and fluid transit time reference table.<ref>Schlumberger Limited, 1984, Schlumberger log interpretation charts.</ref>

|-

|-

! Lithology !! Value (μs/ft) !! Fluid !! Value (μs/ft)

! Lithology !! Value (μs/ft) !! Fluid !! Value (μs/ft)

{| class="wikitable"

{| class="wikitable"

|-

|-

|+ Table 5-Petrophysical properties reference of some sedimentary rocks.

|+ Table 5. Petrophysical properties reference of some sedimentary rocks.

|-

|-

! Lithology !! Gamma Ray (API) !! Spontaneous Potential (mV) !! Resistivity (Ωm) [If shale resistivity is 8] !! Density (gr/cm3)

! Lithology !! Gamma Ray (API) !! Spontaneous Potential (mV) !! Resistivity (Ωm) [If shale resistivity is 8] !! Density (gr/cm3)

==Sources==

==Sources==

* Ijasan, O., Torres-Verdín, C., & Preeg, W. E. (2013). Interpretation of porosity and fluid constituents from well logs using an interactive neutron-density matrix scale. Interpretation, 1(2), T143-T155.

* Ijasan, O., C. Torres-Verdín, and W. E. Preeg, 2013, Interpretation of porosity and fluid constituents from well logs using an interactive neutron-density matrix scale: Interpretation, v.1, no. 2, p. T143-T155.

* Tiab, D., & Donaldson, E. C. (2011). Petrophysics: theory and practice of measuring reservoir rock and fluid transport properties. Gulf professional publishing.

* Tiab, D., and E. C. Donaldson, 2011, Petrophysics: Theory and practice of measuring reservoir rock and fluid transport properties: Gulf Professional Publishing.

* Jorgensen, D. G. (1989). Using geophysical logs to estimate porosity, water resistivity, and intrinsic permeability.

* Jorgensen, D. G., 1989, Using geophysical logs to estimate porosity, water resistivity, and intrinsic permeability.

* Doveton, J. H. (1986). Log analysis of subsurface geology: Concepts and computer methods.

* Doveton, J. H., 1986, Log analysis of subsurface geology: Concepts and computer methods.

* Ellis, D. V., & Singer, J. M. (2007). Well logging for earth scientists (Vol. 692). Dordrecht: Springer.

* Ellis, D. V., and J. M. Singer, 2007, Well logging for earth scientists (Vol. 692). Dordrecht: Springer.

* Muammar, R. (2014). Application of Fluid Mechanics to Determine Oil and Gas Reservoir’s Petrophysical Properties By Using Well Log Data.  

* Muammar, R., 2014, Application of Fluid Mechanics to Determine Oil and Gas Reservoir’s Petrophysical Properties By Using Well Log Data.  

* Balan, B., Mohaghegh, S., & Ameri, S. (1995). State-of-the-art in permeability determination from well log data: part 1-A comparative study, model development. paper SPE, 30978, 17-21.

* Balan, B., S. Mohaghegh, and S. Ameri, 1995, State-of-the-art in permeability determination from well log data: part 1-A comparative study, model development: SPE paper 30978, p. 17-21.

==References==

==References==

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