Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F. 

Form 20-F ___X___ Form 40-F _______

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes _______ No___X____

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Drilling of the fourth well reinforce estimations for Tupi

Rio de Janeiro, November 12 2009 – Petróleo Brasileiro s/a - Petrobras, announces that it has completed the drilling of the fourth well in the Tupi Evaluation Plan area and that the results reinforce the estimations of the estimated volume of 5 to 8 billion barrels of recoverable light oil and natural gas in the pre-salt reservoirs, located in ultra-deep Santos Basin waters.

The well 3-BRSA-755A-RJS (3-RJS-662A) is located 2,115 meters below the water line, nearly 265 km of the coast of Rio de Janeiro, and 18 km northeast of discovery well 1-RJS-628 (1-BRSA-369), known as Tupi.

A thick layer (approximately 250 meters) of light oil-bearing carbonate reservoirs (about 28^o API) was drilled and sampled via cable tests at depths beginning at 4,900 meters.

Formation tests aimed to assess the productivity of the reservoirs are scheduled to begin in the next weeks.

The Consortium, formed by Petrobras (65% - Operator), BG Group (25%) and Galp (10%) to explore block BM-S-11, where Tupi is located, will carry on with the activities and investments contemplated in the Evaluation Plan which was approved by the ANP and which foresees the drilling of additional wells in the area.

 

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www.petrobras.com.br/ri/english
Contacts: PETRÓLEO BRASILEIRO S. A. – PETROBRAS
Investor Relations Department I E-mail: petroinvest@petrobras.com.br / acionistas@petrobras.com.br
Av. República do Chile, 65 – 22^nd floor - 20031-912 - Rio de Janeiro, RJ I Tel.: 55 (21) 3224-1510 / 9947

This document may contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (Securities Act), and Section 21E of the Securities Exchange Act of 1934, as amended (Exchange Act) that merely reflect the expectations of the Company’s management. Such terms as “anticipate”, “believe”, “expect”, “forecast”, “intend”, “plan”, “project”, “seek”, “should”, along with similar or analogous expressions, are used to identify such forecasts. These predictions evidently involve risks and uncertainties, whether foreseen or not by the Company. Therefore, the future results of operations may differ from current expectations, and readers must not base their expectations exclusively on the information presented herein.

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This press release may contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (Securities Act), and Section 21E of the Securities Exchange Act of 1934, as amended (Exchange Act) that are not based on historical facts and are not assurances of future results.  These forward-looking statements are based on management's current view and estimates of future economic circumstances, industry conditions, company performance and financial results. The words "anticipates", "believes", "estimates", "expects", "plans" and similar expressions, as they relate to the company, are intended to identify forward-looking statements. Statements regarding the declaration or payment of dividends, the implementation of principal operating and financing strategies and capital expenditure plans, the direction of future operations and the factors or trends affecting financial condition, liquidity or results of operations are examples of forward-looking statements. Such statements reflect the current views of management and are subject to a number of risks and uncertainties. There is no guarantee that the expected events, trends or results will actually occur. The statements are based on many assumptions and factors, including general economic and market conditions, industry conditions, and operating factors. Any changes in such assumptions or factors could cause actual results to differ materially from current expectations. 
All forward-looking statements are expressly qualified in their entirety by this cautionary statement, and you should not place reliance on any forward-looking statement contained in this press release. We undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information or future events or for any other reason.

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