AVO forward modeling and attributes analysis for fluid’s identification: a case study

Abstract

Since the four decades amplitude versus offset (AVO) analysis is used extensively in hydrocarbon exploration to discriminate the hydrocarbon fluids from background geology. Conventionally AVO analysis involves calculation of intercept and gradient from a linear fit of compressional wave reflection coefficient to the sine square of the angle of incidence. Mississauga formation of early cretaceous is the reservoir rock in the study area, contains hydrocarbons and condensates in the middle part. It is very difficult to discriminate hydrocarbon fluids from non pay zones due to small thickness and low quality of pay zone. AVO forward modeling is done to estimate and analyze various AVO derived attributes for the discrimination of hydrocarbon from background sand. After calculating the AVO attributes, appropriate pairs of these attributes are crossplotted so that the hydrocarbon and non-hydrocarbon facies cluster together for quick identification and interpretation. In intercept/gradient crossplot the top of the gas zone falls in quadrant II and show clear deviation from background trend. The analysis reveals that oil and gas sand attributes are strongly different from water sand attributes. Among various attributes, the fluid factor and intercept are more promising attribute for fluid discrimination.