The Johan Sverdrup field PRM (permanent reservoir monitoring) system has now recorded 2 monitor surveys documenting the progression of the water flood since production and injection began in October 2019 revealing a clear 4D signal linked to the increase in water saturation.

The PRM system was installed in two stages in 2019 and 2020 and is a key component of the reservoir monitoring and data acquisition plan with yearly monitor surveys planned to monitor the water flood development. The first seismic acquisition in 2019, referred to as PRM0, covered the initial first stage of installation on the northern part of the field. Stage two of the installation was completed in 2020 and two monitor surveys have since been acquired covering the entire field, in 2020 (PRM1) and 2021 (PRM2). Clear 4D signals can be seen due to the increase in water saturation and show the waterfront moving updip as it pushes the oil towards the producers.

The Johan Sverdrup field consists primarily of the intra-Draupne sandstone and the secondary Statfjord sandstone reservoirs. The intra-Draupne sandstone has excellent reservoir quality with an average porosity of 28% and permeabilities ranging from 30-70D. The Statfjord sandstone has an average porosity and permeability of 24% and 4D, respectively. The reservoir is undersaturated and has good lateral and vertical communication. These properties lead to a measurable 4D response when water replaces oil as the water flood progresses through the reservoir.

The 4D data is an integral part of the reservoir management program, and together with the geological and production history data, is being used to update the reservoir model to further our understanding of the field development. Examples of the 4D acoustic impedance change generated via a proprietary geostatistical inversion and how it is integrated into the dynamic model will be shown.

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