Mero Reservoir: A Journey of Challenges and Opportunities

Abstract

Abstract A sound data acquisition program together with robustness and flexibility strategies have been planned and performed over 10 years, since Libra Block bid in 2013. The reservoir information obtained during this period led to confirming the commerciality of Mero Field in 2017 and to guiding its development plan, maintaining opportunities for further optimizations during deployment. The main aspects of Mero reservoir and its characterization and drainage strategy are described in this work. Despite its impressive net pay and productivity, Mero reservoir is one of the most complex carbonate reservoirs in the Brazilian Pre-Salt area. Since the first seismic acquisition and the results of the first drilled wells, many uncertainties and challenges were revealed. However, carrying out a detailed data acquisition plan and thus obtaining robust static and dynamic information over the entire field, gradually from the less complex areas towards the most complicated ones, most of these challenges were converted into innovation opportunities for maximizing recovery. Seismic imaging issues due to complex overburden characteristics were tackled with an OBN acquisition followed by several reprocessing and post-processing techniques. Selected development wells were anticipated in strategical reservoir positions, obtaining crucial information on reservoir extension, significant rock diagenesis and presence of igneous bodies within reservoir zones. An itinerant EWT unit, with full gas reinjection, was allocated on main dynamic uncertainty areas, revealing fundamental transmissibility aspects for an adequate hydrocarbon drainage. Analyzing these data altogether made it possible to characterize and model the reservoir in a more precise manner over time, enabling opportunities for drainage plan optimizations. An integrated work between reservoir, subsea, topside and well teams was then essential to transform aspects initially considered as challenges into opportunities. In addition, WAG and intelligent completions will be available in all development wells in order to enhance recovery and mitigate remaining risks regarding heterogeneity. Furthermore, the use of brand-new data for identifying other opportunities did not end at the approval and deployment of the definitive production systems. New data acquisition continues to be carefully planned, such as the use of chemical tracers in every injector well and a Permanent Reservoir Monitoring seismic system to be installed in the next years. The more complex a reservoir is, the more data acquisition and project flexibilities are fundamental for a successful development. Although cost reduction and project acceleration have great value and shall always be pursued, without adequate reservoir modelling, unoptimized decisions are likely to occur and diminish the overall asset value. The concept of the Mero strategy herein presented may be used for the development of other complex offshore projects to maximize its results.