The Magnus Field - Extending Field Life through Good Reservoir Management and Enhanced Oil Recovery

intra Volgian/Kimmeridgian age, of the Magnus Sandstone Member (MSM) and the Lower Kimmeridge Clay Formation (LKCF). The reservoir sandstones of the Magnus Field are enveloped by the organic-rich mudstones of the Kimmeridge Clay Formation that form the source rock. The MSM is dominated by a high net to gross, stacked accumulation of thickbedded fine- to coarse-grained sandstone units (individually about 2 m thick, but occasionally up to 7 m thick) separated by thin shale layers. The main reservoir sands were primarily deposited by high-density turbidity currents although low-density turbidites resulted in deposition of poorer quality sands. In contrast, the LKCF comprises a low net to gross sequence of thin sands (generally 0.1 up to 3m in thickness) separated by thicker shale units representing influx of dilute muddy turbidites with intermittent episodes of sand deposition from high density turbidites. The shale interbeds provide local to field-wide layering of the reservoir and may locally be pressure barriers. In recent wells, the lower parts of each sand package is shown to have been well-swept by waterflood whereas the upper part of the sands has remained relatively unswept. It is this unswept oil that is a key prize for Enhanced Oil Recovery by gas injection.