In the early 2000s the context of the pre-salt formations was conceptual geological models of possible oil bearing reservoirs underneath a thick salt layer, many technical challenges, uncertainties and risks. Past only eight years from first discovery (2006), there are nine production systems, FPSOs, in operation, reaching an average oil rate of more than 700 thousand barrels per day and a cumulative production greater than 400 million barrels of oil, through 34 production wells. To optimize recovery, the first desulfated sea water and gas injectors were started. But these impressive numbers cannot be taken from granted: although nature has revealed prolific reservoirs, much experience, talent, planning and perseverance were necessary.
The first articles addressing the pre-salt fields had a focus on the technical challenges faced on first years: the heterogeneous nature of the microbial carbonate reservoir, the 2,000 m salt layer and drilling concerns associated, the variable CO2 content and compositional grading in the reservoir fluids, flow assurance issues and special demands concerning subsea engineering, well construction and processing plant. The main drivers and development strategies were also established: staged development, based on extended well tests (EWTs), multi well production pilots and definitive systems prioritizing the standardization of well projects and production systems. Now, challenges and plans are rewarding the efforts, as depicted by the concrete production numbers achieved to date.
In this text, a historical perspective of the pre-salt exploration and development is presented, emphasizing the previous unknowns and uncertainties and how they were treated in order to attain the results. As we still have a lot to learn, since we are just on the beginning of the development of this extraordinary petroleum province, a look to the future and the present efforts on optimization are also commented.
