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1. What is XRD Data?

XRD data in petrophysics can represent the percentage of mineral types contained in clay mineral groups and non-clay mineral groups. Several types of clay minerals, such as illite, smectite, and chlorite are often found in XRD data. XRD data can be used for more accurate validation when calculating clay volumes.

Example of XRD data validation in clay and shale volume calculation (Yadav et al., 2012)

2. How to Convert XRD Data?

The XRD data in the report is usually in weighted form, therefore it needs to be converted to volume form. The simple basic formula used is:

$ \rho = \frac{m}{V} $

$ \rho = $ density

$ m =$ mass

$ V =$ volume

Sequentially, the steps required to convert XRD data are:

a. Multiplying the percentage of each mineral in weighted form by the total mass of the sample, to obtain the mass of the mineral per type.

b. Dividing the percentage in weighted form by the density to obtain the volume value

c. Summing up the total volume of clay minerals and the total volume of minerals

d. Dividing the total volume of clay minerals by the total volume of minerals, to obtain the volume of clay in per cent form

e. Convert the percent value to decimal, ready for use in well data processing applications, such as Interactive Petrophysics.

3. Convert XRD Data

📥 Download XRD Conversion Template

Reference: Yadav, L., Dutta, T., & Sinha, N. (2012). Reconciliation of core and log data analysis in very thin reservoirs of Krishna Godavari Basin, India. Society of Petroleum Engineers. https://doi.org/10.2118/149017-MS

A wellstick diagram is a chart that shows the thickness of the markers in each well sorted by interpretation interest. There is a variety of information that we can get from wellstick diagrams such as estimating the direction of deposition and estimating the presence of structures. Wellstick diagrams can be powerful tools for initial geological interpretation. They are often used in reservoir studies, oil and gas exploration, and geological modelling. Usually wellstick diagrams are depicted with stacked bar charts.

Wellstick Diagram Example

Customise Wellstick Diagram

The temperature beneath the surface increases as the depth increases. The data used to calculate the subsurface temperature includes geothermal gradient, depth, and the surface temperature data from the well being evaluated. The formula used to calculate the subsurface temperature is as follows:

T_d = T_s + (G_g × d)

T_d = Temperature at a specific depth
T_s = Surface temperature
G_g = Geothermal gradient
d = Depth

However, if the geothermal gradient data is not available, linear regression can be applied to obtain the geothermal gradient value from the temperature and depth data.

Geothermal Gradient Example

Calculate your Geothermal Gradient and Get the Graph!

Enter the surface and bottom hole temperatures, and depths, to calculate the geothermal gradient and see the graph.

Unit System:

Surface Temperature (°C):

Bottom Hole Temperature (°C):

Surface Depth (m):

Bottom Hole Depth (m):

1. Permeability

Simple equation for permeability:

$log k=P+Q.\phi$

Permeability (k): P constant (P): Q constant (Q): Porosity (Φ):

or:

$log k=P+Q.log\phi$

Permeability (k): P constant (P): Q constant (Q): Porosity (Φ):

2. Permeability from Flow Zone Indicator

Kozeny-Carman Equation:

$k=\frac{\phi^{3}}{(1-\phi)^{3}}\left[\frac{1}{F_{s}.\tau^{2}.S^{2}}\right]$

Permeability (k): Porosity (Φ): Shape factor of the tube (Fs): Tortuosity of the tube (τ): Specific surface area (S):

Reservoir Quality Index:

$RQI=0.0314.\sqrt{\frac{k}{\phi}}$

Reservoir Quality Index (RQI): Permeability (k): Porosity (Φ):

Pore Volume to Grain Volum Ratio:

$\phi _{Z}=(\frac{\phi}{1-\phi})$

ΦZ: Φ:

Flow Zone Indicator:

$FZI=\frac{1}{\sqrt{F_{s}}.\tau.S}$

Flow Zone Indicator (FZI): Shape factor of the tube (Fs): Tortuosity of the tube (τ): Specific surface area (S):

Flow Zone Indicator by Amafeule et al. (1993):

$FZI=\frac{RQI}{\phi _{Z}}$

Flow Zone Indicator (FZI): Reservoir Quality Index (RQI): ΦZ:

Permeability:

$k=1014.(FZI)^{2}.\left(\frac{\phi^{3}}{(1-\phi)^{2}}\right)$

Permeability (k): Flow Zone Indicator (FZI): Porosity (Φ):

3. Permeability from Porosity and Irreducible water saturation

Wyllie and Rose (1950):

$k=\frac{P.\phi^{Q}}{Swi^{R}}$

Permeability (k): P constant (P): Porosity (Φ): Q constant (Q): Irreducible water saturation (Swi): R:

Timur (1968):

$k=\frac{0.136.\phi^{4.4}}{Swi^{2}}$

Permeability (k): Porosity (Φ): Irreducible water saturation (Swi):

4. Permeability from Nuclear Magnetic Resonance (NMR)

Schlumberger-Doll Research (SDR):

$k=a.T_{2gm}^{2}.\phi^{4}$

Permeability (k): Formation scaling parameter (a): Principal pore radius (T2gm): Porosity (Φ):

Coates et.al (1991):

$k=(\frac{\phi _{NMR}}{C})^{a}.(\frac{FFI}{BVI})^{b}$

Permeability (k): NMR effective porosity (ΦNMR): FFI: BVI:

Reference:

https://www.linkedin.com/company/the-petroleum-paradise/

1. Porosity

Simple equation for total porosity:

Kalkulator Porositas

$\phi=\frac{Vp}{Vb}$

Total porosity (Φ): Volume of void space (Vp): Bulk volume of the rock (Vb):

2. Porosity from density log

Kalkulator Porositas dari Log Densitas

$\rho_{bulk}=\phi.\rho_{fluid}+(1-\phi).\rho_{matrix}$

Bulk density (ρ_bulk): Porosity (Φ): Matrix density (ρ_matrix): Fluid density (ρ_fluid):

Kalkulator Porositas dari Log Densitas II

$\phi_{density}=\frac{\rho_{matrix}-\rho_{bulk}}{\rho_{matrix}-\rho_{fluid}}$

Porosity (Φ_density): Bulk density (ρ_bulk): Fluid density (ρ_fluid): Matrix density (ρ_matrix):

Fluid density if the formation is the hydrocarbon bearing:

Kalkulator Porositas dari Log Densitas II

$\rho_{fluid}=\rho_{mf}.S_{xo}+\rho_{hc}(1-S_{xo})$

Fluid density (ρ_fluid): Density of the mud filtrate (ρ_mf): Saturation of the mud filtrate in the invaded zone (Sxo): Hydrocarbon density (ρ_hc):

Total porosity estimate:

Kalkulator Porositas dari Log Densitas

$\rho_{bulk}=\phi.\rho_{fluid}+V_{sh}.\rho_{sh}+(1-V_{sh}-\phi).\rho_{matrix}$

Bulk density (ρ_bulk): Porosity (Φ): Fluid density (ρ_flu): Shale density (ρ_sh): Volumetric estimate of shale proportion (Vsh): Matrix density (ρ_matrix):

Correct the total porosity to the effective porosity:

Kalkulator Porositas dari Log Densitas III

$\phi_{e}=\phi_{t}-V_{sh}.\phi_{dsh}$

Effective porosity (Φ_e): Total porosity (Φ_t): Shale density (Φ_sh): Volume of shale (V_sh):

3. Porosity from neutron-density log

Kalkulator Porositas dari log neutron density

$\phi_{e}(ND)=\frac{\phi_{Neutron}+\phi_{Density}}{2}+V_{sh}+\frac{\phi_{nsh}+\phi_{dsh}}{2}$

Effective porosity (Φ_e): Neutron porosity log readings (Φ_Neutron): Density porosity log readings (Φ_Density): Volume of shale (V_sh): Shale density (Φ_nsh): Density of shale (Φ_dsh):

4. Porosity from sonic log

The linear interpolation (Willye et.al., 1956):

Kalkulator Porositas dari log sonic

$\phi _{sonic}=\frac{\Delta t-\Delta t_{matrix}}{\Delta t_{fluid}-\Delta t_{matrix}}$

Total porosity from sonic log (Φ_sonic): Acoustic travel time log measurement (Δ_t): Matrix transit time which depend on the lithology of the rock (Δ_{t matrix}): Pore fluid transit time (Δ_{t fluid}):

Raymer-Hunt-Gardner(RHG) transform:

Kalkulator Porositas dari log sonic II

$\frac{1}{\Delta t}=\frac{\phi}{\Delta t_{fluid}}+\frac{1-\phi}{\Delta t_{matrix}}$

Total porosity (Φ): Acoustic travel time log measurement (Δ_t): Matrix transit time which depend on the lithology of the rock (Δ_{t matrix}): Pore fluid transit time (Δ_{t fluid}):

5. Shale volume (Vsh) from neutron density

Kalkulator Porositas dari log sonic

$V_{sh(ND)}=\frac{\phi _{Neutron}-\phi _{Density}}{\phi _{nsh}-\phi _{dsh}}$

Volume of shale (V_sh): Neutron porosity log (Φ_Neutron): Total porosity from density log (Φ_Density): Neutron porosity of shale (Φ_nsh): Density porosity of shale (Φ_dsh):

6. Gamma Ray

Expectation of the API unit log reading of a shale:

Kalkulator Gamma Ray

$GR_{Total}=8U(ppm)+4Th(ppm)+16K(%)$

Gamma ray total (GR_total): Uranium (U): Thorium (Th): Kalium (K):

Analysis of the North American shale composite (NASC) reference standard (Gromet et.al., 1984):

Kalkulator Gamma Ray II

$GR_{Total}=12.3Th(ppm)+2.66U(ppm)+3.2K(%)=121.7APIunit$

Gamma ray total (GR_total): Uranium (U): Thorium (Th): Kalium (K):

7. Shale volume (Vsh) from Gamma Ray

Kalkulator Porositas dari log sonic

$V_{sh}=\frac{GR-GR_{min}}{GR_{max}-GR_{min}}$

Volume of shale (V_sh): Gamma ray (GR): Gamma ray maximum (GR_max): Gamma ray minimum (GR_min):

Larionov equation on Tertiary rock:

Kalkulator Larionov equation

$V_{sh}=0,083.(2^{3,7058-GRI}-1)$

Volume of shale (V_sh): Gamma ray index (GRI):

Larionov older rocks:

Kalkulator Larionov older rocks

$V_{sh}=0,33.(2^{GRI}-1)$

Volume of shale (V_sh): Gamma ray Index (GRI):

If clay volume was the issue:

Kalkulator Larionov older rocks

$V_{cl}=0,6.V_{sh}$

Volume of clay (V_cl): Volume of shale (V_sh):

Steiber equation:

Kalkulator Stieber

$V_{sh}=\frac{3.GRI}{(1+2.GRI)}$

Volume of shale (V_sh): Gamma ray index (GRI):

Kalkulator Stieber

$V_{sh}=\frac{GRI}{(1+c.(1-GRI))}$

Volume of shale (V_sh): Gamma ray index (GRI): (c):

c = 1 → Vsh with the gamma ray index (GRI)

c = 2 → older rocks

c = 3 → Tertiary rocks

Reference:

https://www.linkedin.com/company/the-petroleum-paradise/

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Customise Wellstick Diagram

Calculate your Geothermal Gradient and Get the Graph!

1. Permeability

Simple equation for permeability:

or:

2. Permeability from Flow Zone Indicator

Kozeny-Carman Equation:

Reservoir Quality Index:

Pore Volume to Grain Volum Ratio:

Flow Zone Indicator:

Flow Zone Indicator by Amafeule et al. (1993):

Permeability:

3. Permeability from Porosity and Irreducible water saturation

Wyllie and Rose (1950):

Timur (1968):

4. Permeability from Nuclear Magnetic Resonance (NMR)

Schlumberger-Doll Research (SDR):

Coates et.al (1991):

1. Porosity

Simple equation for total porosity:

2. Porosity from density log

Fluid density if the formation is the hydrocarbon bearing:

Total porosity estimate:

Correct the total porosity to the effective porosity:

3. Porosity from neutron-density log

4. Porosity from sonic log

The linear interpolation (Willye et.al., 1956):

Raymer-Hunt-Gardner(RHG) transform:

5. Shale volume (Vsh) from neutron density

6. Gamma Ray

Expectation of the API unit log reading of a shale:

Analysis of the North American shale composite (NASC) reference standard (Gromet et.al., 1984):

7. Shale volume (Vsh) from Gamma Ray

Larionov equation on Tertiary rock:

Larionov older rocks:

If clay volume was the issue:

Steiber equation:

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