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The development of deep and ultra deepwater fields, especially in marginal areas, always presents challenges related to profitability and/or flow assurance related issues for subsea equipment. Currently, Petrobras has a great number of production wells operating in ultra deep waters, thereby is constantly looking forward to improve its production capacity and reduce its operational expenditures (OPEX) as well. In order to address the challenge of reducing both OPEX and CAPEX (capital expenditures) when focusing low GOR scenarios, Petrobras has developed a new application for a conventional ESP, the so called Mudline ESP. This innovative technology can be used in large scale to boost oil production from marginal/ remote wells located in deep waters fields.A prototype Mudline ESP was tested in the Petrobras Atalaia test site to investigate the flow behavior of the system (e.g.: start up with high gas conditions), to determine the maximum allowable GVF and its behavior when powered by a single three phase electrical cable, besides gauging other effects. After its manufacture, the SIT (System Integration Test) was performed in Atalaia test site as well. After SIT the Prototype Mudline ESP was installed (Dec, 2011) in the Espadarte field (Campos Basin) in a water depth of 1300 m to boost the production during an extended well test. The field performance of the Mudline ESP in Espadarte was above the expectations. These positive results gave confidence in the Mudline ESP, that becomes an extra option for subsea boosting in Petrobras. Soon, this new pumping concept will be operating in both Chinook and Cascade fields in the Gulf of Mexico (GoM) area.

In the scenario of deepwater, specially in the case of marginal oilfields, the industry faces the challenge of making the exploitation developments technically viable and cost effective, to guarantee the success of the project even in a scenario with considerably variable oil price. To make possible the profitable development of such oilfields and increase the project net present value, it is required to keep the capital and operational expenditures (CAPEX andOPEX) within reasonable limits, at the same time that leading edge technology is necessary. At a first glance it seems contradictory and a question naturally arises: is low cost deepwater development a dream or a possibility? No doubt it is a big challenge. For CAPEX reduction, the first suggestion for marginal fields is the elimination of exclusive/dedicated production platform and the adoption of subsea systems tied-in to existing infrastructure. In Campos Basin, where several fields lay in the same neighborhood, Petrobras had experienced the possibility of starting a production from one oil well in Albacora Leste field, exporting to a platform located in the neighbor Albacora field. The RJS-477A well, located in 1109 meters of water depth, had the production boosted by electrical submersible pump (ESP) and directed to P-25 platform located 6.5 km away. Although not being a long distance tie-in, the technology developed allows for the consideration of such boosting technology in the viability studies being conducted for other fields. Besides the boosting technology using ESP, that could be nowadays called a mature technology, other nonconventional ones are being studied inside Petrobras, focused on the deepwater scenarios, with the objective of verifying their economical impact and attractiveness. The combination of mature and non-conventional technologies is believed to be the best approach to make marginal field development profitable. This paper presents some Petrobras realization in marginal field and deepwater field developments and discusses how mature and new technologies may be combined aiming the exploitation of marginal fields. Introduction Since the early days of offshore oil production the industry has been facing the problem of increasing costs of the infrastructure according to the water depth. In order to assure the cost-effectiveness of the projects higher production rates were sought. In most cases these high production rates demanded larger, heavier and more costly process plants and platforms, which increased the costs even more. Several technological innovations were introduced in a logical series to keep CAPEX whitin economical limits. Firstly, it was carried out the reduction of the amount of wells per production unit by means of higher productivity. Secondly, floating production systems were adopted as jackets costs grew exponentially with the water depth. The quest for lower deckloads has lead to the ever more frequent use of subsea wells. Next step was the installation of subsea manifolds, which reduced the length (and cost) of subsea lines as well as the number and, most important, the weight of risers hanging from the platforms.