The integrated use of 3D seismic data, well information and seismic forward modelling – Lake Hope field area

Abstract

The Lake Hope 3D survey was acquired in 1992 and covers five producing oil fields in the Lake Hope Block of the South Australian sector of the Cooper/Eromanga Basins. A total of 38 wells have been drilled within the survey limits, of which 24 are currently producing from eight different reservoir levels. The bulk of the production comes from the Early Cretaceous/Namur Sandstone and Jurassic Birkhead Formation, Hutton Sandstone and Poolowanna Formation. The reservoirs occur between 1.2 and 1.5 seconds two way time (1300?1800 m below MSL). The excellent quality of the Lake Hope 3D seismic data and the large number of wells in the area allowed extensive use of seismic forward modelling. The object was to better understand the quality and distribution of the various reservoirs in the area. Integration of well data, seismic amplitude information and production history made it possible to define the presence and extent of producing Birkhead Formation sands. Two dimensional forward modelling was utilised to interactively alter well-logs and observe the corresponding change in seismic response. By using these procedures and horizon slices from the 3D seismic volume it was possible to prognose additional areas where similar sands are likely to be present. The Hutton Sandstone reservoir contains over one quarter of the oil within the Lake Hope Fields and is also a very productive reservoir elsewhere in the Eromanga Basin. The Birkhead Formation is the top seal to this unit and the Birkhead/Hutton Interface marks the change from the high energy braided stream environment of the Hutton Sandstone to the lacustrine/low energy fluvial environment of the Birkhead Formation. This interface varies from an abrupt change to a transitional change over a 10 metre interval. Reservoir quality and pay thickness are heavily dependent on the nature of this transition. Well information was correlated with observed seismic response to establish the character of the Birkhead/Hutton Interface within the area of the 3D seismic survey. The above studies demonstrate the importance of integrating geological information, well production history and observed variations in seismic response to fully utilise 3D seismic data.