Santos Basin Presalt-Reservoirs Development

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 19953, "Santos Basin's Pre-Salt Reservoirs Development - The Way Ahead," by J.M.F. Filho, SPE, A.C.C. Pinto, SPE, and A.S. de Almeida, SPE, Petrobras, originally prepared for the 2009 Offshore Technology Conference, Houston, 4–7 May. The paper has not been peer reviewed. The full-length paper describes the current studies for the future development of the presalt reservoirs in the Santos basin presalt cluster in deepwater offshore Brazil. Development of the area is divided into three phases. The first phase is a dynamic information-gathering phase comprising extended well tests and production pilots. The second phase, extending to 2017, will comprise conventional subsea completion systems. The third phase will consider nonconventional solutions. Introduction The area known as the presalt cluster, in the Santos basin, is in ultradeep water between 1900 and 2400 m, approximately 290 km offshore the Rio de Janeiro coast in southeast Brazil. Fig. 1 shows the main blocks of the presalt cluster, currently in the appraisal-plan phase. At the beginning of the current century, the "cluster blocks" in the Santos basin were considered one of the most important exploration frontiers of the Brazilian continental shelf, given the size of the structures and the perfect seal created by the salt layer. In 2002, as the operator of different consortia, Petrobras obtained, through a bid process, the concession to explore several blocks in the Santos basin area. The first location, known as Parati (RJS-617), was approved in March 2004. At that time, just two wells had been drilled in the proximal portion of the basin, having crossed thick intervals of the presalt section. The existence of source rocks with characteristics similar to those found in the Campos basin was inferred through geochemical correlations, but there was significant uncertainty regarding the maturation, migration, and volumes that could have been generated and trapped. Despite these uncertainties, the most important risks associated with the locations were related to the existence and quality of the reservoirs. The Parati location was intended to test the stratigraphic traps in multiple objectives in the post-salt section and, additionally, to test a domic structure in the presalt. The sandstone reservoirs above the salt contained water, and the decision was made to go ahead with the well. After drilling 500 m of basalt, with several operational problems, the well drilling stopped at 7600 m true vertical depth subsea (TVDSS). Gas condensate was found in reservoirs of the presalt, confirming the presence of a petroleum system in the area, stimulating the drilling of RJS-628 in the presalt, which resulted in the Tupi discovery.