Underbalanced drilling (UBD) is a drilling technique in which hydrodynamic pressure, exerted by the drilling mud and circulating fluids in the well bore, is below the pressure of the well formation. In UBD applications the surface pressure is lower than the well pressure, resulting in the flow of hydrocarbons to the surface at a controlled rate. This drilling technique requires specialized surface equipment for continuous separation of the drilling mud and hydrocarbon components for recirculation, sampling, storage, flaring, and disposal. Underbalanced Drilling technology provides significant technical and economical value and reduces damage to the well formation. This paper highlights how custom-off-the-shelf technology provided a cost-effective solution where Petrobras was able to reduce the time required to reach full production and eliminate or reduce, the fracturing required after a well is completed.

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