Drilling and completing either exploratory or development wells in Pre-Salt prospects present several challenges. The wells are located in very deep waters, beyond 2,000 m WD and they are also deep wells, with more than 5,000 m TVD. Pressure and temperature is normal, but contaminants such as H2S and CO2 represent an additional difficulty. Most of all, drilling through salt layers as thick as 2,000 m presents the most challenging aspect of these wells. Directional, extended reach (ERW), horizontal and multilateral wells will be evaluated for production development, but the reservoir is a carbonate horizon just below the salt, meaning that high angle navigation and multilateral joints will be located inside the salt layers. These wells measured depths will reach 8,000 m or more. The salt geo-mechanical loads on the casing and cementing will require high strength materials and high capacity rig equipment. The competency of the salt formations and, most of all, of the carbonate reservoir, totaling more than 3,000 m to be drilled, will require special BHA and bit design to increase penetration rates, thus reducing rig time. Carbonate reservoir will require production liner, perforations/slots and stimulation treatments designed to maximize production. Although these challenges could be overcome today, with existing technology, due to the current high costs scenario, well construction time and risks must be minimized. Some technology development is already underway to address these issues, but most of the gains can be materialized without new technology, by proper engineering design, risk management and learning curve acceleration. After 8 wells drilled in Pre-Salt prospects, Petrobras has already gained important know-how in these projects, but there is still a long way ahead. In the following years, well construction campaign for an Extended Well Testing (EWT) and a Pilot Production System in the Tupi Pre-Salt area, plus additional exploration wells, will provide field test opportunities for development and optimization of well engineering techniques and equipment. This paper will present the highlights of Petrobras E&P program to make the best use of these opportunities to leverage the well construction learning curve. Introduction In recent years, exploration activities in Brazil began to focus on the São Paulo Plateau, a prominent regional topographic feature in water depths ranging from 2,000 to 3,000 m. A continuous Aptian evaporitic sequence, in some points thicker than 2,000 m (Fig. 1), exists in this region, contrasting with the very thin marine section above. The reservoir section occurs just below the evaporitics and is composed by microbialite carbonates. In such a Pre-Salt section, with variable thickness, a few exploratory wells were drilled. Petrobras is now facing a challenge similar to that one encountered during the discoveries of deep-water turbiditic reservoirs in Campos Basin. Salts belong to a group of sedimentary rocks called evaporites, resulting from sea water evaporation. Submitted to a sustained constant stress, evaporites can suffer considerable deformation, in a behavior denominated " salt creeping??. Due to this characteristic, salt intrusions and domes can be found in many sedimentary basins, associated with either high pore pressure zones, or fractured zones (" rubble zones??).

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Since 1978, when the first subsea well in Campos Basin came on stream, more than 210 subsea trees, 22 subsea manifolds and 2000 kms of umbilicals plus flowlines have been installed and operated on this site. To achieve this universe, not only significant break-throughs in the applied technologies were necessary, but mainly the development of a management philosophy to guarantee an optimal cost/benefit relation had to be implemented. Total Quality Control (TQC) was chosen for this purpose, and several operational procedures, data failure banks and respective statistical analysis were established to provide tools for the managers to achieve the desired goals. This paper presents several of this control mechanisms, their evolution through time and some other TQC applications such as: service contract models, functional specifications for subsea manifolds and standardization of subsea trees interfaces, highlighting the savings gained throughout all these years. With a subsea activity average CAPEX and OPEX budget of US$ 500 MM per year, and a subsea oil production of approximately 500,000 BOPD Campos Basin is a good example of the applicability of TQC practices in the search of economical development of offshore fields, specially those ones in deep water sites. Introduction Not so long ago, subsea activity was considered a "display window" for Oil Operators technological capacity, without concern about the real economical benefit of this kind of exploitation. These were the flourishing times, when the oil price could stand the wastes created by fancy design practices. Nowadays this attitude is no longer accepted: as in any other industry, Oil Operators are facing challenges every day, to assure market competitiveness. According to a recent research [Ref. 1], in well managed E & P divisions, the waste of time and money may achieve 30 to 40 percent. Those who can reduce these percentages will certainly guarantee a leading position in the oil business. Meanwhile, subsea technology itself is no more an experimental knowledge arena, becoming an effective tool for oil fields development. The economical impact of this conception can be seen in Fig. 1, where one can verify that the share related to subsea technology (including drilling and completion operations) corresponds to approximately 67% of the total CAPEX of a typical deep water project. Approximately 15 years ago, Petrobras faced the compulsiveness to start exploitation in deep waters, since it was the only alternative to crude importations. Brazilian reserves are located in increasingly water depths and the company survival is linked to the development of these fields in a competitive and profitable way; a challenge which most Operators are experiencing only now. Today, most Operators are facing similar challenges. The charts on Figs. 2, 3 and 4 (Brazilian reserves, oil geological potential and production profile) show the importance of deep waters for Petrobras:–59 % of the present reserves are located in water depths greater than 400 meters.–66 % of potential new discoveries are expected to occur on the same range of water depth.–Future production profile also shows the importance of oil flow originated from those sites. Besides new developments, Petrobras has already a significant amount of installed subsea facilities, which demands careful operational management. Fig. 5 shows a summary of present and future installations in deep waters. P. 379