Reservoir Management Decisions Supported by 4D Seismic in a Brazilian Pre-Salt Field: A Well Crossflow Correction Case

This work aims to present a significant gain in reservoir management by using 4D seismic data in a Pre-salt field of the Santos Basin. The focus is to demonstrate how the interpretation of these data can support decisions that optimize production and mitigate fluid flow-related issues in the field. The time-lapse interpretation in this field was based on three seismic acquisitions: a 2012 streamer, a 2021 Ocean Bottom Node (OBN), and another OBN from 2023. The first 4D processing was carried out using the 2021 OBN data as the monitor and the 2012 streamer data as the baseline (T1). Although the repeatability between these datasets was low, the hybrid processing provided relevant information about the start of production. Subsequently, a high repeatability 4D processing was performed using the 2021 and 2023 OBN acquisitions (T2), enabling the monitoring of fluid flow continuity. The combination of interpretations from both time periods (T1 and T2), together with production data, enabled the identification of a crossflow phenomenon in a producer well that was shut-in. This phenomenon caused early water breakthroughs in adjacent wells, an issue that was only detected through 4D imaging, as the well lacked sensors capable of indicating such an anomaly. The interpretation was validated with production data, but it was the 4D seismic that identified the anomaly, leading to a revisit of the production data. This work presents a detailed account of how the phenomenon was identified, based on the integration of 4D seismic data, pressure data, and water cut from the adjacent wells. Furthermore, an adjusted reservoir simulation is presented, representing both the phenomenon and the expected gains resulting from the proposed workover in the affected well, highlighting its positive impact on adjacent wells. The presented case illustrates how the implementation of seismic monitoring can yield substantial gains, particularly for reservoir management, which are especially difficult to predict during the approval phase of 4D projects.