Deepwater Brazilian Presalt: The Way Ahead for Research and Development

Abstract

Academia - The way ahead for research and development in the deepwater Brazilian presalt. The era of easy oil is gradually coming to an end. Over the last 5 years, the big discoveries around the globe have been in areas with complex geology that are not easy to access and, in most cases, present logistical difficulties. One of the most promising of these regions is the so-called Golden Triangle, which includes offshore US Gulf of Mexico, offshore Brazil, and offshore western Africa. These areas lie in deep or ultradeep waters, ranging from 2000 to 3000 m, and are below a considerable layer of salt rock—up to 2000 m thick in the Brazilian case. The reservoir geology is also complex, ranging from microbial carbonates to dolomitized limestones to intercalated sandstones. Exploiting these resources in a costeffective manner presents a number of challenges for the industry, which I shall discuss as they relate to offshore Brazil. Reservoir Imaging Presalt reservoir imaging and characterization are the starting points for achieving a successful development campaign. Although it has improved during the past few years, reservoir imaging still poses big challenges to operators and service companies offshore Brazil. Room for further improvement certainly exists. The high reflectiveness of the postsalt/salt interface leads to major attenuations of the seismic signal, jeopardizing vertical resolution. Additionally, the salt layer heterogeneity, composed of halite intercalated with layers of anhydrite, carnalite, and tachyhydrite, brings additional hurdles to the modeling of the velocity cube, which is used in the time-depth conversion. The reservoir carbonate rock also presents a high degree of heterogeneity, with important insertions of silica nodes and, at least until now, an unknown fracture pattern, in addition to the need for better understanding of pore size distribution and connection.