HOUSTON, TX--(Marketwire - Jul 20, 2011) - TGS will commence acquisition of multi-client 3D seismic data in offshore Sierra Leone later this month. This survey marks over ten years of investment for TGS in the West African region and will add 2,535 km2 to the existing TGS data library. The new 3D seismic will provide important data for continued exploration on the Sierra Leone segment of the West Africa Transform Margin, where recent discoveries have established that a working hydrocarbon system exists.

The M/V GeoCarribean will acquire the 2011 survey. Data processing will be performed by TGS and available to clients in Q1 2012.

The survey is supported by industry funding.

Company summary
TGS-NOPEC Geophysical Company (TGS) provides multi-client geoscience data and services to oil and gas Exploration and Production companies around the globe. TGS' geophysical and geological data products include multi-client seismic libraries, permanent reservoir monitoring, magnetic and gravity data, the industry's largest global database of digital well logs and regional interpretive products. TGS also provides high-end depth imaging services to help resolve complex seismic imaging problems. For more information visit TGS online at www.tgsnopec.com.

Forward-looking statements and contact information
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).

Contact Information:

For additional information about this press release please contact:

Kristian Johansen
Chief Financial Officer
Office: +47 667 69931
Cell: +47 47 60 33 34
Email:

Karen El-Tawil
VP, Business Development
Office: +1 713 860 2102
Cell: +1 713 806 2420
Email:

Juan M. Santana
Regional Director, Africa/Middle East
Office: +1 713 860 2140
Email: