In the Gulf of Mexico, many gas-saturated sands are not Bright Spots and thus are difficult to detect on conventional 31) seismic data. These small amplitude reflections occur frequently in Pliocene-Miocene exploration plays when the acoustic impedances of the gas-saturated sands and shales are approximately the same. In these areas, geophysicists have had limited success using AVO to reduce the exploration risk. The interpretation of the conventional AVO attributes is often difficult and contains questionable relationships to the physical properties of the media. A 3D AVO study was conducted utilizing numerous well-log suites, core analyses, and production histories to help calibrate the seismic response to the petrophysical properties. This study resulted in an extension of the AVO method to a technique that now displays Bright Spots when very clean sands and gas-saturated sands occur. These litho-stratigraphic reflections on the new AVO technique are related to Poisson's ratio, a petrophysical property that is normally mixed with the acoustic impedance on conventional 3D migrated data.
展开▼
