Impact of 4D FWI for development and production of a Brazilian presalt carbonate reservoir

Abstract The use of 4D seismic data for increasing production and recovery factor (RF) in siliciclastic oil field reservoirs is well established. However, in the carbonate rocks of the Brazilian presalt, which are stiff, deep (approximately 5 km), and heterogeneous, the 4D signal is weaker and presumably would require higher repeatability between base and monitor acquisitions. In a pilot project with streamer (preproduction) and nodes acquisitions, processing algorithms were tested to overcome the low repeatability. The 4D full-waveform inversion (FWI) proved to be effective in providing high-quality 4D signal related to saturation variations in the field. The surprisingly high quality of the fast-track data already provided information on layer property variations in a shorter time than conventional workflows. The results highlight the impact of 4D FWI on the management and development of a presalt field in Brazil. Gas saturation variations were confidently interpreted, as well as the rise of the oil-water contact. Preferred permeability directions are being refined, and this set of information allows for greater robustness in adjustments of geologic and flow models and better positioning of new injectors and producers. The results of this study pave the way for the application of 4D FWI in other presalt fields, potentially amplifying the economic impact.