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The next obvious step is to look at the AVO response with the sand
saturated with oil and gas to see how the AVO changes with depth and
with different fluids. Gassmann's Relations Gassmann (1951) are used
to transform the data.
| |
(5) |

and
| |
(6) |

where *K*_{min} is the bulk modulus of the mineral, *K*_{fl} is the bulk moduli
of the fluid, *K*_{1} is the bulk modulus of the rock saturated with the
original fluid (water in this case), *K*_{2} is the bulk modulus of the rock
with fluid substitution, is porosity, and is the shear modulus.
To find the new moduli, recompute the velocities with the equations:
| |
(7) |

| |
(8) |

From the preliminary look at the AVO response, it was difficult, if not
impossible, to detect any changes in the amplitude as a function of offset. The
AVO of the same depths with gas and oil as the saturating fluid were almost
identical to the water saturated images. This aspect of the project will,
therefore, need to be studied further before any conclusive results can be stated.

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Stanford Exploration Project

11/11/1997