A2D signs well log data agreement with Chesapeake Energy Corporation

12 September 2005

Houston, Texas (12 September, 2005) - A2D Technologies, a TGS-NOPEC Company, announced today that it has secured a comprehensive well log data agreement with Chesapeake Energy Corporation.

Terms of the five year agreement include a subscription for unlimited access to A2D's industry-standard depth-calibrated smartRASTER® well log database. Additionally, Chesapeake will partner with A2D to further expand the A2D commercial digital LAS log library.

"Our extended agreement with A2D is an important part of Chesapeake's digital data strategy to increase exploration success," commented Mark Lester, Senior Vice President of Exploration for Chesapeake. "Having unlimited, readily-available access to well log data for our geoscientists is essential to staying competitive in today's market."

"This agreement expands a long-standing and positive relationship between our two companies", stated Rod Starr, Executive Vice President Sales & Marketing for A2D. "Chesapeake joins a steadily growing list of leading energy companies who take full advantage of online access to A2D's complete well log database in the U.S."

A2D Technologies, a wholly-owned subsidiary, is the energy industry's well log data marketplace offering the largest online database, immediate delivery, conversion services, data management services and worldwide well log data sourcing. The TGS family of companies places a strong emphasis on providing high-quality data and the highest level of service to the industry. 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 that are difficult to predict, and are based upon assumptions as to future events that may not prove accurate. These factors include TGS' reliance on a cyclical industry and principal customers, TGS' ability to continue to expand markets for licensing of data, and TGS' ability to acquire and process data products at costs commensurate with profitability. Actual results may differ materially from those expected or projected in the forward-looking statements. TGS undertakes no responsibility or obligation to update or alter forward-looking statements for any reason. TGS-NOPEC Geophysical Company ASA is listed on the Oslo Stock Exchange (OSLO:TGS).