Stress Adjustment Models

digirock.StressAdjust

Base stress adjustment class

Implements modulus adjustments for bulk modulus, shear modulus. Updates methods for density, vp and vs.

Classes which inherit this class should implement the modifications to the bulk and shear moduli.

Attributes:

Name	Type	Description
transform_keys	tuple(str, ...	The props keys this model needs for performing the transform.
element	Element	The element to transform
stress_model	StressModel	The stress model to use for effective stress
name	str	Name of the model

__init__(self, transform_keys, element, stress_model, name=None) special

Parameters:

Name	Type	Description	Default
transform_keys	Sequence[str]	The props keys this model needs for performing the transform.	required
element	Type[digirock._base.Element]	The element to transform	required
stress_model	Type[digirock._stress.StressModel]	The stress model to use for effective stress	required
name	str	Name of the model	None

bulk_modulus(self, props, **kwargs)

Applies the class porosity adjustment to the bulk modulus.

density(self, props, **kwargs)

Returns density of RockFrame using volume fraction average, see [mixed_denisty][digirock.models._mod.mixed_density].

Parameters:

Name	Type	Description	Default
props	Dict[str, Union[numpy.ndarray, float, int]]	A dictionary of properties required.	required
kwargs		ignored	{}

Returns:

Type	Description
Union[numpy.ndarray, float]	density (g/cc)

shear_modulus(self, props, **kwargs)

Applies the class porosity adjustment to the shear modulus.

vp(self, props, **kwargs)

Returns compression velocity of RockFrame

Parameters:

Name	Type	Description	Default
props	Dict[str, Union[numpy.ndarray, float, int]]	A dictionary of properties required.	required
kwargs		ignored	{}

Returns:

Type	Description
Union[numpy.ndarray, float]	velocity (m/s).

vs(self, props, **kwargs)

Returns shear velocity of RockFrame

Parameters:

Name	Type	Description	Default
props	Dict[str, Union[numpy.ndarray, float, int]]	A dictionary of properties required.	required
kwargs		ignored	{}

Returns:

Type	Description
Union[numpy.ndarray, float]	velocity (m/s).

digirock.MacBethStressAdjust

Adjustment model for modulus based upon MacBeth's stress response model in a sandstone rock frame.

\[ \kappa(P) = \frac{\kappa_\inf}{1 + E_\kappa e^{\tfrac{-P}{P_\kappa}}} \]

\[ \mu(P) = \frac{\mu_\inf}{1 + E_\mu e^{\tfrac{-P}{P_\mu}}} \]

This implementation removes estimates for \(\kappa_\inf\) and \(\mu_\inf\) by substituting in an initial pressure see dryframe_delta_pres.

Attributes:

Name	Type	Description
e_k	float	e exponent bulk modulus
p_k	float	p exponent bulk modulus
e_mu	float	e exponent shear modulus
p_mu	float	p exponent shear modulus

Refs

MacBeth, C., 2004, A classification for the pressure-sensitivity properties of a sandstone rock frame, Geophysics, Vol 69, 2, pp497-510, doi:10.1190/1.1707070

__init__(self, transform_keys, element, stress_model, e_k, p_k, e_mu, p_mu, name=None) special

Parameters:

Name	Type	Description	Default
transform_keys	Sequence[str]	The props keys this model needs for performing the transform.	required
element	Type[digirock._base.Element]	The element to transform	required
stress_model	Type[digirock._stress.StressModel]	The stress model to use for effective stress	required
e_k	float	e exponent bulk modulus	required
p_k	float	p exponent bulk modulus	required
e_mu	float	e exponent shear modulus	required
p_mu	float	p exponent shear modulus	required
name	str	Name of the model	None

bulk_modulus(self, props, **kwargs)

This implementation removes estimates for \(\kappa_\inf\) by substituting in an initial pressure see dryframe_delta_pres.

Parameters:

Name	Type	Description	Default
props	Dict[str, Union[numpy.ndarray, float, int]]	props dict requires at least pres and pres_init.	required
**kwargs		ignored	{}
Returns		bulk_modulus	required

shear_modulus(self, props, **kwargs)

This implementation removes estimates for \(\mu_\inf\) by substituting in an initial pressure see dryframe_delta_pres.

Parameters:

Name	Type	Description	Default
props	Dict[str, Union[numpy.ndarray, float, int]]	props dict requires at least pres and pres_init.	required
**kwargs		ignored	{}

Returns:

Type	Description
	shear modulus