Abstract

In the 90's, after success in drilling wells deeper than 5,000 meters with high production rates between 80 to 120 MMSCFD of production, Petrobras decided to continuously measure pressure on their high productivity wells (7″ production tubing) because of the difficulty they experienced when running gauges in the production mode after the wells were completed.

Therefore, the decision was made to use permanent electronic gauges to obtain downhole pressure as it was a proven technology and optical sensing technology (fiber optics) was new to the industry. At that time, four wells in the San Antonio and San Alberto fields were completed with electronic gauges with different results….one did not work, one failed at the beginning, one failed months later, and one worked intermittently.

Petrobras' objective to have real time downhole pressure did not change, and they planned for the next workovers of their wells to use optical sensing technology instead of electronic gauges. These specifications were required on their next bid, and the four wells were assigned to Weatherford International. Since that time, this technology is working in the four wells in the San Antonio and San Alberto fields, and there have only been small problems on surface equipment connections, which were corrected promptly.

Because of this success, Petrobras decided last year to implement optical sensing technology in all of their new wells because it was the only proven technology that could support the high vibration, produced by the 7″ tubing wells, and high temperature. The decision was taken one step further to install fiber optic downhole flowmeters on the intelligent completion wells. The use of this technology, complemented with the online PanSystem™ well test analysis software, enables real time well testing.

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