Multidisciplinary Approach Underpins Development of Marginal Presalt Reservoir

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 35273, “Sururu Central: Appraisal and Development Plan for a Marginal Presalt Reservoir,” by Thiago E.S. Azevedo, L.M. Hayashi, and Rodrigo R.S. Leal, SPE, Petrobras, et al. The paper has not been peer reviewed. Copyright 2024 Offshore Technology Conference. _ The complete paper presents a multidisciplinary view of the evolution of the concept of a development project for the central area of the Sururu reservoir and the method applied to address challenges and propose solutions. The central area presents distinct characteristics from typical Brazilian presalt fields, with low permeabilities despite high porosity. Sururu Reservoir The reservoir is in the Santos Basin 230 km offshore Rio de Janeiro at water depths ranging from 2000 to 2300 m. The wildcat in the reservoir, 1-BRSA-618-RJS (1-RJS-656), is in the central area of the field, which is the main subject of the present work. The well exhibited reasonably high average porosity while presenting low permeabilities and low productivity when compared with other presalt wells. The second well, 3-BRSA-891A-RJS (3-RJS-682A), was drilled in 2011 in an area known as Iara Horst, also in the central area of the Sururu reservoir and presenting the same challenges faced by the wildcat. The third well, 3-BRSA-1181D-RJS (3-RJS-715D), was drilled in 2013 as a high-angle multifractured well consisting of an alternative architecture. Productivity results, however, were similar to the ones obtained in the previous wells. Investments were made in acquiring and reprocessing seismic data, ultimately leading to the drilling of the fourth well, 9-BRSA-1212-RJS (9-RJS-726). This well, in the Sururu Oeste area, revealed characteristics more similar to other Brazilian presalt fields and cleared the path to the later drilling of other Sururu Oeste wells. These good results paved the way for floating production, storage, and offloading (FPSO) vessel Petrobras 68 (P-68), which has produced both the Berbigão and Sururu reservoirs since November of 2019. P-68 is a 150,000-BOPD, 6-million std m³/d gas processing “replicant” FPSO that includes 10 producers (five from Berbigão and five from Sururu) and seven injectors (four in Berbigão and three in Sururu). However, the idea of developing an alternative for producing the Sururu Central area was never abandoned. In 2020, the ninth Sururu well and the fourth well in the central area, 9-SRR-5-RJS, was drilled near some of the main Sururu Central faults, aiming to test the existence of better reservoir quality or the presence of conductive in-situ fractures. The results from the well were in line with the results from the previous three wells drilled in the area, confirming the challenging nature of Sururu Central productivity. A suitable development strategy for the area was increasingly dependent on the attainment of long-term dynamic data that could support a modeling hypothesis for this unique presalt reservoir.