Abstract: Direct Hydrocarbon Identification Using AVO Analysis in the Malay Basin

Yue Choong Lye, Nigel E. Birkett, Mohd. Raji Yaacob, M. Reza Daneshvar

Esso Production Malaysia Inc. and Petronas Carigali Sdn. Bhd. have been conducting AVO (amplitude versus offset) processing and interpretation since April 1991 in an attempt to identify hydrocarbon fluids predrill. The major part of this effort was in the PM-5, PM-8, and PM-9 contract areas where an extensive exploration program is underway. To date, more than 1000 km of seismic data have been analyzed using the AVO technique, and the results were used to support the drilling of more than 50 exploration and delineation wells.

Gather modeling of well data was used to calibrate and predict the presence of hydrocarbon in proposed well locations. In order to generate accurate gather models, a geophysical properties and AVO database was needed, and great effort was spent in producing an accurate and complete database. This database is continuously being updated so that an experience file can be built to further improve the reliability of the AVO prediction.

Statistical analysis of AVO results in the Malay Basin indicates a 65% chance of observing a favorable AVO response, i.e., an increase of amplitude with offset/angle for hydrocarbon-bearing sands and a decrease for wet sands. Inconsistent AVO responses have been documented to be caused by (1) physical properties of rocks not supporting an AVO anomaly, (2) poor processing, (3) poor signal to noise ratio, and (4) presence of tight streaks.

Within the industry, application of the AVO technique has often led to high expectations that have not been realized. However, with careful assessment and applying the right approach, AVO analysis can help lower the risk in hydrocarbon exploration.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994