Gravity effect of any rock slab above the datum can be reduced by 'Bouguer plate correction'. If I understand your question correctly you'll need the sediment density and the thickness of the layer to calculate its gravity effect. Have a look at the link attached :

http://web.ics.purdue.edu/~ecalais/teaching/eas450/Gravity4.pdf

Dear Arka Das Thanks for giving your suggestion.

but here I have to calculate gravity anomaly contribution of sediment not the gravity effect of sediment which can be calculated as you told considering it as bouguer plate.

Hi Akhil,

It seems the estimated gravity anomaly value is a result of several factors from which you want to remove the effect of a particular sedimentary layer, is this the problem? Can you elaborate more?

use parkers method..

Akhil Mishra and colleagues: it is a very interesting question.

Another way could be a blend between prestack simultaneous elastic inversion with gravity modeling.

The elastic inversion is a method to estimate the three basic properties of the subsurface: Vp, Vs and density. In elastic inversion, density is recognized to be very hard to recover. This trouble is consequences from the design and acquisition parameters, the processing, the density and thickness contract of the layers, between others. But you need remember that the density changes are involved in the seismic final responses (creates both P-wave and S-wave scatterings reflection) in the subsurface. Knott (1899) and Zoeppritz (1919) deduced the expressions for the reflection of compression and shear waves at a boundary as a function of the densities and velocities of layers in contact. It means: the stresses and displacement across the boundary of elastic media. I put emphasis in the word "elastic": the fact that in general our layer-models interpretation is simple, sometimes so far from the real and more complex ones, e.g., subsurface is non-isotropic, non-homogeneous, and non-elastic layers, you may have irregularities in the final answer of the density in focus.

In any case, if you estimate a density model from an elastic-simultaneous prestack seismic inversion, you could incorporate the result obtained in the gravity modeling and inversion programs and estimate the gravity sedimentary-layer responses in a more approximate way to reality.

I show you in the attached figure an example taken from a real case in which I am working, in which I illustrate the comparison that exists between the values ​​of Vp, Vs and density measured in a borehole (well-logs) and those obtained from an prestack elastic simultaneous inversion. After that, you need to convert a whole seismic volume (3D) or line (2D) in a whole sedimentary thickness / window of interest. It means: you could recovery the gravity answer by an individual sedimentary window or all the section.

Remember that in my answer you need to have: prestack seismic and well-logs togheter, to get the density layer-cake response and modelling in a gravity program. Also, you need a very good quality-control of all the input data, step-by-step, e.g., the wells, the logs, the inversion-window, the iteractions, the final inversion output.

Best regards, Mario E. Sigismondi

Sorry, please, I do not explain the color lines in the picture.

From left to right:

In the first track, the P-impedance (P-wave velocity by density); then, the S-impedance (S-wave velocity by density); next the density; the error in the 4th track and the wavelet (blue) to finish with the seismic (red).

In the P-S impedance and density tracks, the red curves are the model response estimating from prestack simultaneous elastic seismic inversion and the "real" measurement values of Vp, Vs and density are in blue color, but filtering at seismic frequencies bandwidth.

Mario

Hi Akhil! You will need a grid of sediment thinkness (meter or kilometer) as an input. Then, you will need a softwate to calculate the series for the convergence and obtain the resulting Gravity Effect of Sediments (try Lithoflex software).

After all this steps, just subtract your gravity anomaly grid from the gravity effect sedimens grid.

Cheers!