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Pitfalls in seismic amplitude versus offset analysis - case histories

Conference · · Am. Assoc. Pet. Geol., Bull.; (United States)
OSTI ID:6982598
A new seismic technology, called by such names as seismic lithology, amplitude versus offset (avo), and Poisson's ratio analysis, has been effective in reducing exploration risks for gaseous hydrocarbons. However, as with all technologies, pitfalls can lead to incorrect interpretation of these common-depth-point gathers. The Terra Linda Group, Inc., used the SAMPLE method of analysis, and categorized the pitfalls into three groups: data collection, data processing and geologic. For example, in data collection, geophone and shot arrays are either not as described or are not recorded (as in the Sacramento basin), thereby masking true amplitudes. When processing data, true amplitude versus offset anomalies are lost because automatic gain control is a default parameter in many processing steps. Also, improper scaling after the mix or stack will alter amplitudes. Geologic pitfalls include shallow reflectors, which can mask the amplitude versus offset anomalies from deeper hydrocarbons (as in the Denver-Julesburg basin or the Sacramento Valley), or calcium carbonate-cemented gas sands, which can show amplitude decreases with offset and therefore are overlooked (as in the gulf of Mexico). Detailed modeling such as the SAMPLE method prevents many of these pitfalls from giving false hydrocarbon indications. Other pitfalls must be recognized and properly factored in when evaluating the risk of an individual seismic anomaly.
Research Organization:
Terra Linda Group, Inc., San Anselmo, CA
OSTI ID:
6982598
Report Number(s):
CONF-8604187-
Conference Information:
Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 70:4
Country of Publication:
United States
Language:
English