Petrophysics

This section contains documentation for the Petrophysics module.

Porosity

stoneforge.petrophysics.porosity.density_porosity(rhob: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], rhom: float, rhof: float) → ndarray

Estimate the porosity from the bulk density log [1]_.

Parameters

rhobarray_like

Bulk density log.

rhomint, float

Matrix density.

rhofint, float

Density of the fluid saturating the rock (Usually 1.0 for water and 1.1 for saltwater mud).

Returns

phiarray_like

Total porosity for the aimed interval using the bulk density.

References

[1]

Schön, J. H. (2015). Physical properties of rocks: Fundamentals and

principles of petrophysics. Elsevier.

stoneforge.petrophysics.porosity.gaymard_porosity(phid, phin)

Estimate the effective porosity using Gaymard-Poupon [1]_ method.

Parameters

phidarray_like

Density porosity (porosity calculated using density log)

phinint, float

Neutron porosity (porosity calculated using neutron log)

Returns

phiearray_like

Effective porosity using Gaymard-Poupon method

References

[1]

Gaymard, R., and A. Poupon. “Response Of Neutron And Formation

Density Logs In Hydrocarbon Bearing Formations.” The Log Analyst 9 (1968).

stoneforge.petrophysics.porosity.neutron_density_porosity(phid: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], phin: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], squared: bool = False) → ndarray

Estimate the effective porosity by calculating the mean of Bulk Density porosity and Neutron porosity [1]_.

Parameters

phidarray_like

Effective porosity and shale free for the aimed interval using the bulk density.

phinarray_like

Effective porosity from the neutron log for the aimed interval.

Returns

phiearray_like

Effective porosity from the Bulk Density porosity and Neutron porosity mean.

References

TODO

stoneforge.petrophysics.porosity.neutron_porosity(nphi: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], vsh: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], nphi_sh: float) → ndarray

Estimate the effective porosity from the neutron log [1]_.

Parameters

nphiarray_like

neutron log.

vsharray_like

Total volume of shale in the rock, chosen the most representative.

phi_nshint, float

Apparent porosity read in the shales on and under the layer under study and with the same values used in φN.

Returns

phinarray_like

Effective porosity from the neutron log for the aimed interval.

References

[1]

Schön, J. H. (2015). Physical properties of rocks: Fundamentals and

principles of petrophysics. Elsevier.

stoneforge.petrophysics.porosity.porosity(method: str = 'density', **kwargs)

Compute porosity from well logs.

This is a façade for the methods:

• density

• neutron

• neutron-density

• sonic

• gaymard

Parameters

rhobarray_like

Bulk density log. Required if method is “denisty”.

rhomint, float

Matrix density. Required if method is “denisty”.

rhofint, float

Density of the fluid saturating the rock (Usually 1.0 for water and 1.1 for saltwater mud). Required if method is “denisty”.

nphiarray_like

Neutron log. Required if method is “neutron”.

vsharray_like

Total volume of shale in the rock, chosen the most representative. Required if method is “neutron”.

phi_nshint, float

Apparent porosity read in the shales on and under the layer under study and with the same values used in φN. Required if method is “neutron”.

dtarray_like

Sonic log reading (acoustic transit time (μsec/ft)). Required if method is “sonic”.

dtmaint, float

Acoustic transit time of the matrix (μsec/ft). Required if method is “sonic”.

dtfint, float

Acoustic transit time of the fluids, usually water (μsec/ft). Required if method is “sonic”.

phidarray_like

Density porosity (porosity calculated using density log). Required if method is “neutron-density” or “gaymard.

phinint, float

Neutron porosity (porosity calculated using neutron log). Required if method is “neutron-density” or “gaymard.

methodstr, optional

Name of the method to be used. Should be one of

• ‘density’

• ‘neutron’

• ‘neutron-density’

• ‘sonic’

• ‘gaymard’

If not given, default method is ‘density’

Returns

phiarray_like

Porosity log using the defined method.

stoneforge.petrophysics.porosity.sonic_porosity(dt, dtma, dtf)

Estimate the Porosity from sonic using the Wyllie time-average equation [1]_.

Parameters

dtarray_like

Sonic log reading (acoustic transit time (μsec/ft))

dtmaint, float

Acoustic transit time of the matrix (μsec/ft)

dtfint, float

Acoustic transit time of the fluids, usually water (μsec/ft)

Returns

phidtarray_like

Porosity from sonic.

References

[1]

13. 18. 10. Wyllie, A. R. Gregory, and L. W. Gardner, (1956), “ELASTIC WAVE VELOCITIES IN HETEROGENEOUS AND POROUS MEDIA,” GEOPHYSICS 21: 41-70.

Shale Volume

stoneforge.petrophysics.shale_volume.gammarayindex(gr: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], grmin: float, grmax: float) → ndarray

Calculates the gamma ray index.

Parameters

grarray_like

Gamma Ray log.

grminint, float

Clean sand GR value.

grmaxint, float

Shale/clay value.

Returns

igrarray_like

The gamma ray index varying between 0.0 (clean sand) and 1.0 (shale).

stoneforge.petrophysics.shale_volume.vshale(gr: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], grmin: float, grmax: float, method: str = None) → ndarray

Compute the shale volume from gamma ray log.

This is a façade for the methods:

• vshale_linear

• vshale_larionov

• vshale_larionov_old

• vshale_clavier

• vshale_stieber

Parameters

grarray_like

Gamma Ray log.

grminint, float

Clean sand GR value.

grmaxint, float

Shale/clay value.

methodstr, optional

Name of the method to be used. Should be one of

• ‘linear’

• ‘larionov’

• ‘larionov_old’

• ‘clavier’

• ‘stieber’

If not given, default method is ‘linear’

Returns

vshalearray_like

Shale Volume for the aimed interval using the defined method.

stoneforge.petrophysics.shale_volume.vshale_clavier(gr: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], grmin: float, grmax: float)

Estimate the shale volume from the Clavier model.

Parameters

grarray_like

Gamma Ray log.

grminint, float

Clean sand GR value.

grmaxint, float

Shale/clay value.

Returns

vshalearray_like

Shale Volume for the aimed interval using the Clavier method.

stoneforge.petrophysics.shale_volume.vshale_larionov(gr: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], grmin: float, grmax: float) → ndarray

Estimate the shale volume from the Larionov model for young rocks.

Parameters

grarray_like

Gamma Ray log.

grminint, float

Clean sand GR value.

grmaxint, float

Shale/clay value.

Returns

vshalearray_like

Shale Volume for the aimed interval using the Larionov method.

stoneforge.petrophysics.shale_volume.vshale_larionov_old(gr: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], grmin: float, grmax: float) → ndarray

Estimate the shale volume from the Larionov model for old rocks.

Parameters

grarray_like

Gamma Ray log.

grminint, float

Clean sand GR value.

grmaxint, float

Shale/clay value.

Returns

vshalearray_like

Shale Volume for the aimed interval using the Larionov method.

stoneforge.petrophysics.shale_volume.vshale_linear(gr: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], grmin: float, grmax: float) → ndarray

Estimate the shale volume from the linear model.

Parameters

grarray_like

Gamma Ray log.

grminint, float

Clean sand GR value.

grmaxint, float

Shale/clay value.

Returns

vshalearray_like

Shale Volume for the aimed interval using the Linear method.

stoneforge.petrophysics.shale_volume.vshale_neu_den(neu: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], den: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], cl1_n: float = -0.15, cl1_d: float = 2.65, cl2_n: float = 1.0, cl2_d: float = 1.1, clay_n: float = 0.47, clay_d: float = 2.71) → ndarray

Estimates the shale volume from neutron and density logs method [1]_.

Parameters

neuarray_like

Neutron porosity log.

denarray_like

Bulk density log.

cl1_nint, float

Neutron porosity value from clean point 1 for empty matrix (NPHI_MATRIX).

cl1_dint, float

Bulk density value from clean point 1 for empty matrix (RHOB_MATRIX).

cl2_nint, float

Neutron porosity value from clean point 2 full porosity.

cl2_dint, float

Bulk density value from clean point 2 full porosity.

clay_nint, float

Neutron porosity value from clay point (NPHI_SHALE).

clay_dint, float

Bulk density value from clay point (RHOB_SHALE).

Returns

vshalearray_like

Shale volume from neutron and density logs method.

References

[1]

Bhuyan, K., & Passey, Q. R. (1994). Clay estimation from GR and

neutron-density porosity logs. In SPWLA 35th Annual Logging Symposium. OnePetro.

stoneforge.petrophysics.shale_volume.vshale_stieber(gr: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], grmin: float, grmax: float)

Estimate the shale volume from the Stieber model.

Parameters

grarray_like

Gamma Ray log.

grminint, float

Clean sand GR value.

grmaxint, float

Shale/clay value.

Returns

vshalearray_like

Shale Volume for the aimed interval using the Stieber method.

Water Saturation

stoneforge.petrophysics.water_saturation.archie(rw: float, rt: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], phi: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], a: float, m: float, n: float) → ndarray

Estimate the Water Saturation from Archie’s [1]_ equation.

Parameters

rwint, float

Water resistivity.

rtarray_like

Formation resistivity.

phiarray_like

Porosity.

aint, float

Tortuosity factor.

mint, float

Cementation exponent.

nint, float

Saturation exponent.

Returns

swarray_like

Water saturation from Archie equation.

References

[1]

Archie GE (1942) The electrical resistivity log as an aid in determining some

reservoir characteristics. Transactions of the AIME, 146(01), 54-62.

stoneforge.petrophysics.water_saturation.fertl(rw: float, rt: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], phi: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], a: float, m: float, vsh: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], alpha: float) → ndarray

Estimate water saturation from Fertl [1]_ equation.

Parameters

rwint, float

Water resistivity.

rtarray_like

True resistivity.

phiarray_like

Porosity (must be effective).

vsharray_like

Clay volume log.

aint, float

Tortuosity factor.

mint, float

Cementation exponent.

alphaint, float

Alpha parameter from Fertl equation.

Returns

fertlarray_like

Water saturation from Fertl equation.

References

[1]

Fertl, W. H. (1975, June). Shaly sand analysis in development wells. In SPWLA 16th Annual Logging Symposium. OnePetro.

stoneforge.petrophysics.water_saturation.indonesia(rw: float, rt: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], phi: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], a: float, m: float, n: float, vsh: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], rsh: float) → ndarray

Estimate water saturation from Poupon-Leveaux (Indonesia) [1]_ equation.

Parameters

rwint, float

Water resistivity.

rtarray_like

True resistivity.

phiarray_like

Porosity.

vsharray_like

Clay volume log.

aint, float

Tortuosity factor.

mint, float

Cementation exponent.

nint, float

Saturation exponent.

rshfloat

Clay resistivity.

Returns

indonesiaarray_like

Water saturation from Poupon-Leveaux equation.

References

[1]

Poupon, A. and Leveaux, J. (1971) Evaluation of Water Saturation in Shaly Formations.

The Log Analyst, 12, 1-2.

stoneforge.petrophysics.water_saturation.simandoux(rw: float, rt: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], phi: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], a: float, m: float, n: float, vsh: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], rsh: float) → ndarray

Estimate water saturation from Simandoux [1]_ equation.

Parameters

rwint, float

Water resistivity.

rtarray_like

True resistivity.

phiarray_like

Porosity.

aint, float

Tortuosity factor.

mint, float

Cementation exponent.

nint, float

Saturation exponent.

vsharray_like

Clay volume log.

rshint, float

Clay resistivity.

Returns

swarray_like

Water saturation from Simandoux equation.

References

[1]

Simandoux P (1963) Measures die techniques an milieu application a measure des

saturation en eau, etude du comportement de massifs agrileux. Review du’Institute Francais du Patrole 18(Supplemen-tary Issue):193

stoneforge.petrophysics.water_saturation.water_saturation(rw: float, rt: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], phi: Buffer | _SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes], a: float, m: float, method: str = 'archie', **kwargs) → ndarray

Compute water saturation from resistivity log.

This is a façade for the methods:

• archie

• simandoux

• indonesia

• fertl

Parameters

rwint, float

Water resistivity.

rtarray_like

True resistivity.

phiarray_like

Porosity (must be effective).

aint, float

Tortuosity factor.

mint, float

Cementation exponent.

nint, float

Saturation exponent. Required if method is “archie”, “simandoux” or “indonesia”.

vsharray_like

Clay volume log. Required if method is “simandoux”, “indonesia” or “fertl”.

rshfloat

Clay resistivity. Required if method is “simandoux” or “indonesia”.

alphaarray_like

Alpha parameter from Fertl equation. Required if method is “fertl”

methodstr, optional

Name of the method to be used. Should be one of

• ‘archie’

• ‘simandoux’

• ‘indonesia’

• ‘fertl

If not given, default method is ‘archie’

Returns

water_saturationarray_like

Water saturation for the aimed interval using the defined method.