ABSTRACT: Just a Bright Spot?

MASUDA, RANDALL M., Exploration Consultant, Calgary, Alberta, Canada

Seismic has always been a valuable tool for hydrocarbon exploration. Its value for defining limits of structural traps has been proven over the past few decades. Digital technology has allowed increased fidelity of data. With the advent of true amplitude processing, much stratigraphic information can be inferred from amplitude analysis and complex trace attribute analysis. This includes bed thickness and gross rock properties (acoustic impedance).

However, seismic technology has advanced even further with a new analysis method. Ostrander (1984) showed a method that predicts the presence of gas. Ostrander showed that amplitude variations of events within a CMP gather may be used to predict lithology and pore content of reservoirs. Over the past few years, this has evolved beyond a quantitative tool or merely looking for AVO changes and relating these to lithology and pore content of the reservoirs. AVO analysis also includes predicting known geologic situations by AVO forward modeling of geologic well logs and estimating rock parameters by AVO inverse modeling (inversion).

An example is shown of all three aspects: interpretation of AVO data, forward modeling, and inverse modeling. The example is a Bright Spot, which is analyzed for reservoir characteristics. The Bright Spot is one with classic characteristics: high amplitude reflection, phase reversal, and time sag. However, analysis of complex trace attributes shows a complicated result. AVO analysis reveals an even more striking view of the placid Bright Spot. Results are rather surprising and should change our perception of Bright Spots.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)