Press Releases

TGS commences a second 3D multi-client seismic survey offshore Northwest Australia

PERTH, AUSTRALIA  (20 December 2011) - TGS has commenced acquisition of a new 3D multi-client seismic survey, Mary Rose Northeast,  which covers 3,100 km2 over the Exmouth Plateau in the Carnarvon Basin, offshore NW Australia.  This survey is located over parts of blocks WA-365-P, WA-346-P and W10-21 to the Northeast of the previously announced NW Australia survey (Mary Rose) in October 2011.  Upon completion of this survey, the TGS portfolio of 3D multi-client coverage in this highly prospective area offshore Australia will exceed 11,500 km2.

The seismic data is being acquired by the M/V Geo Atlantic and will be complete in Q1 2012.  A fast track volume will be available to the industry in Q2 2012 with final data available for the full survey in Q4 2012.  The survey is supported by industry funding.

Mary Rose 3D Ext 120911

About TGS

TGS provides multi-client geoscience data to oil and gas Exploration and Production companies worldwide. In addition to extensive global geophysical and geological data libraries that include multi-client seismic data, magnetic and gravity data, digital well logs, production data and directional surveys, TGS also offers advanced processing and imaging services, interpretation products, and data integration solutions.

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 product 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.

Sven Børre Larsen

Sven Børre Larsen

Chief Financial Officer

Tel: +47 90 94 36 73

Ellen Munkvold

Ellen Munkvold

IR Coordinator

Tel: +47 97 76 26 25