PRESTACK INTERCEPT & GRADIENT SCALING TO THE MODELED SYNTHETIC AN EXAMPLE FROM HEIDRUN FIELD, NORTH SEA

PROCEEDINGS JOINT CONVENTION SURABAYA 2005 – HAGI-IAGI-PERHAPI
The 30^th HAGI, The 34^th IAGI, and The 14^th PERHAPI Annual Conference and Exhibition

PRESTACK INTERCEPT & GRADIENT SCALING TO THE MODELED SYNTHETIC
AN EXAMPLE FROM HEIDRUN FIELD, NORTH SEA

Nguyen Nam
Landmark Graphics, Kuala Lumpur, Malaysia & Larry Fink, Landmark Graphics, Denver, USA
ABSTRACT

Calibration is the key to successful amplitude vs. offset (AVO) analysis to identify fluid and lithology changes using prestack seismic data. A common AVO crossplot shows the attributes of “intercept” and “gradient” help to separate different lithologies and/or fluids. To move from qualitative anomaly analysis of prestack to quantitative analysis–classifying how oil, gas, or brine appear on the pre stack data–it is necessary to scale the real data to the modeled synthetic data. In this paper, we consider a scaling process that matches the magnitudes of intercept and gradient events extracted from the real data to the intercept and gradient of the modeled data. A case study is presented, demonstrating this process of matching real prestack gathers to the log-generated gathers in a 2D crossplot. The scaled data are then used to compare anomalous intercept-gradient data points that represent lithologic and/or pore fluid changes from the background data throughout the entire 3D survey.