rockphypy.Emp

Module Contents

Classes

Empirical

Empirical relations that widely applied

class rockphypy.Emp.Empirical

Empirical relations that widely applied

static krief(phi, Kg, Gg)

Compute porous background elastic constants as a function of porosity according to Krief model.

Parameters:

• phi (float or array) – porosity in porous rock

• Kg (float) – grain bulk modulus

• Gg (float) – grain shear modulus

Returns:

float or array – lamda,G,K

static esti_VS(Vp, vsh)

Estimate, using the Greenberg-Castagna empirical relations, the shearwave velocity in a brine-saturated shaly sandstone with vp since we only assume two minearl phases: so L=2, X1= 1-vsh, X2= vsh

Parameters:

• Vp (float or array-like) – compressional velocities, m/s

• vsh (float or array-like) – shale volume

Returns:

• float or array-like – vs (m/s): estimated shear wave velocities

• References – ———-

• - handbook of rock physics P516

static han(phi, C)

Han (1986) found empirical regressions relating ultrasonic (laboratory) velocities to porosity and clay content.effective pressure is 20Mpa

Parameters:

• phi (float or array-like) – porosity

• C (float or array-like) – clay volume fraction

Returns:

float or array-like – P and S wave velocities

static ehrenberg(Z)

porosity reference trend for Norwegian Sea sandstone. Note that the functional form of the porosity model is not published in Ehrenberg (1990). It is obtained by linear regression of the digitized data point from the original plot in the paper.

Parameters:

Z (float or array) – burial depth below see floor in Km

References

Ehrenberg, S., 1990, Relationship between diagenesis and reservoir quality in sandstones of the Garn Formation, Haltenbanken, mid-Norwegian continental shelf: AAPG bulletin, 74, no. 10, 1538

Returns:

float or array – porosity

static yu_segment_trend(Z)

Reference trend for Norwegian sea normally buried clean sandstones

Parameters:

Z (float or array) – burial depth below see floor in m

Returns:

float or array – P wave velocities

static ramm_porosity(Z, HB=True)

porosity reference trend according to Ramm & Bjørlykke (1994)

Parameters:

• Z (float or array) – burial depth wrt. sea floor in m

• HB (bool, optional) – if True: only show the regression line for halten bakken area porosity data False: The regression line for all porosity from north sea and norwegian sea, by default True

Returns:

float or array – porosity

static ramm_porosity_segment(Z)

segment porosity reference trend according to Ramm & Bjørlykke (1994) considering the mechanical and chemical compaction

Parameters:

Z (float or array) – burial depth wrt. sea floor in m

Returns:

float or array – porosity

static empirical_StPeter(Pe, sample=1)

compute the Vp and Vs for st peter sandstone using the empirical relationship in the form of V= A+KPe-Be^(-DPe)

Parameters:

• Pe (float or array) – effective pressure in Kbar, 1kbar= 100Mpa

• sample (int, optional) – 1-sample 1, phi= 0.205. 2-sample 2, phi= 0.187, by default 1

Returns:

float or array – Vp,Vs in km

static Scherbaum(Z)

velocity depth trend for Lower and Middle Buntsandstein

Parameters:

Z (float or array) – burial depth wrt. sea floor in m

References

Scherbaum, F., 1982. Seismic velocities in sedimentary rocks—indicators of subsidence and uplift?. Geologische Rundschau, 71(2), pp.519-536.

Returns:

float or array – P wave velocities in m/s

static Sclater(phi)

Sclater-Christie exponential curve for sandstone

Parameters:

phi (float or array) – porosity

Returns:

Z (float or array) – depth wrt. sea floor in km.

static Storvoll(Z)

Storvoll velocity compaction trend. The trend is for shale and shaly sediments but also used for siliciclastic rock like sandstone

Parameters:

Z (float or array) – depth wrt. sea floor in m.

Returns:

float or array – Vp meters per second

static Hillis(Z)

compaction trend for Bunter Sandstone in North sea

Parameters:

Z (float or array) – depth below sea bed (in kilometers)

Returns:

float or array – Vp km/s

static Japsen(Z)

a segmented linear velocity–depth function, These equations are considered as approximation for bunter sandstone trend although they are originally for bunter shale. proposed by Japsen 1999

Parameters:

Z (float or array) – depth below sea bed in m.

Returns:

float or array – Vp m/s

static hjelstuen(Z)

Velocity-depth relationships for the Bjørna-Sørkapp margin deposits. note: the seismic velocities are not directly comparable with velocities from sonic logs (because of the different frequencies), and the velocity-depth profile of Hjelstuen et al. (1996) has not been corrected for uplift and erosion

Parameters:

Z (float or array) – Z< 3.8km

Returns:

float or array – V: m/s

static Cp(phi)

The coordination number n depends on porosity, as shown by Murphy 1982.

Parameters:

phi (float or array) – total porosity , for a porosity of 0.4, n=8.6

Returns:

float or array – coordination number