TGS-NOPEC Geophysical Company, via its subsidiary, A2D Technologies, completed the acquisition of all shares of Riley Electric Log Inc from the Canadian corporation Divestco Inc. on December 5th, 2003.

In addition to Riley's entire U.S. well log data inventory, A2D received a perpetual license from Divestco to market approximately 1.2 million depth-calibrated images of Canadian well logs. Terms of the license allow A2D to develop and own added value and derivative products from the Canadian well log images.

Riley Electric Log owns the most extensive (3 million+) collection of hard-copy well logs in the U.S. These well logs, in addition to the 1.2 million Canadian well logs, will greatly expand A2D's industry-leading digital well log database, LOG-LINE Plus!

This comprehensive data coverage will allow A2D to source materials for existing backlogged orders, add to A2D's client base, and further substantiate and grow A2D's existing subscription model. Riley's financial results will be consolidated with A2D's results beginning in January 2004. The Riley acquisition is expected to increase A2D's 2004 revenues by at least 30% over 2003 levels.

TGS-NOPEC is a leading global provider of multi-client geoscience data and associated products and services to the oil and gas industry. TGS-NOPEC specializes in the planning, acquisition, processing, interpretation, and marketing of non-exclusive seismic surveys worldwide. The TGS-NOPEC group places a strong emphasis on providing high quality data and the highest level of service to the industry.

A2D Technologies, a wholly owned subsidiary of TGS-NOPEC Geophysical Company, pioneered the delivery of digital well log data over the Internet and currently offers a one-of-a-kind integrated solution for well log data sourcing, well log data management, and well log correlation.

All statements in this press release other than statements of historical fact are forward-looking statements, which are subject to a number of risks, uncertainties and assumptions. These include TGS-NOPEC's reliance on a cyclical industry and principal customers, the company's ability to continue to expand markets for licensing of data, and the company's ability to acquire and process data products at costs commensurate with profitability. Actual results may differ materially from those expected or projected. TGS-NOPEC undertakes any duty to update forward-looking statements.