Heavy Oil Recovery in Potiguar Basin, Brazil: Steamflooding from Field Pilot Testing to Commercial Application

Abstract Northeastern Brazil, in the fields of Fazenda Belém, Estreito and Alto do Rodrigues. Shortly after discovery, they were stepwise and successfully put into production through steam cycling. However, upon trying to convert this operation to steamflooding via two field pilots in selected areas of Fazenda Belém and Alto do Rodrigues, where cycling had reached the economic limit, the results left much to be desired. The operation was suspended and production maintained by the original steamcycling program by expanding it into new areas of the fields. Based on the fact that the two steamflooding field pilot attempts were on patterns of 5 and 2½ acres, respectively, it was thought that reservoir heterogeneity, among other issues, could be responsible for the two consecutive failures. Consequently, a third pilot was decided upon, this time in a specific area of Estreito. Some 1,600 MMB of 15-16ºAPI OOIP were discovered in the early eighties, onshore Potiguar Basin, field. New wells were drilled for this purpose, defining four adjacent and inverted nine-spot patterns of 1¼ acre each. It was the year of 1993, when a project was approved in the portfolio of PRAVAP-Petrobras Strategic Advanced Oil Recovery Program, to design and implement the Estreito steamflooding pilot test, together with other related lines of research focused on the heavy oil accumulations in Potiguar Basin. Five years, 32,000 man-hours, and US$2.3 million later, the results were so encouraging that prompted the decision by the Operational Unit to initiate the corresponding study to scale-up the pilot test not only to the entire Estreito field but also to the neighboring, Alto do Rodrigues. In addition, this enterprise took into consideration the installation of a gas fired thermoelectric plant for the co-generation of steam and electricity, as to enhance the economic feasibility potential. This paper presents the results of the PRAVAP project, as well as the production forecasts for the ongoing effort to expand the steamfloding operation to the commercial scale in those two fields.