Value of Additional Oil Development Wells in the Bookabourdie Field: a Combined Geological and Reservoir Engineering Approach
Engineering Honours Degree 2007
University of Adelaide
A combined geologic and engineering approach was used to address size and connectivity issues of sandy reservoirs within a fluvio-lacustrine sequence in the South Australian part of the Eromanga Basin. The approach was not wholly successful as the necessary pressure data over the interval of interest was found to be inadequate. Nonetheless, a geologic analysis, fundamentally based on well log interpretations was carried out to tackle fluvial reservoir sand distribution issues within the Middle to Late Jurassic Birkhead Formation in the Bookabourdie area.
A new chronostratigraphic framework for the Mesozoic succession, developed in-house at Santos, facilitated the definition and subsequent subdivision of the Birkhead Formation into separate units. Sand percent calculations within each subdivision, as defined by particular GR cut offs, were transformed into a set of sand fraction maps by utilising a specialised commercial software package. These maps failed, however, to clearly resolve fluvial channel patterns in the area. Subsequent well-to-well correlations of the interpreted fluvial lithofacies packages across the field led to the development of a conceptual sand distribution model. This model, coupled with recently acquired 3D seismic data interpretation has the potential to put some constraints on the future oil development drilling activities in the Bookabourdie area targeting these fluvial reservoirs.
The lack of adequate pressure data prevented well connectivity evaluation or application of any meaningful material balance calculations. However, a preliminary historical field production data examination indicated the possibility of two historical producers belonging to a single connected system. Given some secondary drive mechanisms (e.g. waterflood) are implemented in the future, there is potential for reinstating the historical Jurassic oil producers. Further investigation is needed however, to assess the re-pressurisation and fluid recharge levels especially in terms of the economic return on such a project.
Three types of surface facilities have been identified as possible options for the planned Bookabourdie Field oil development. After consideration of economic, environmental and operational aspects, an optimal choice was identified and recommended. Subsequently, three appraisal/development drilling scenarios were analysed in terms of economics and a minimum economic pool size (MEPS) for each scenario was found.
The potential performance of the Birkhead reservoirs in the Bookabourdie area was inferred on the basis of analogy by inspecting total recoveries in other productive areas in the South Australian part of the Cooper Basin. This approach showed the P90 and P10 estimates of well productivities to range from 13 to 220 MSTB. The P50 recoveries were found to be approximately 55 MSTB, considerably lower than the minimum economic pool size requirement for the single well scenario of 95 MSTB.