The Turrum Field—Reeling in the Latest Fish on the Line

Abstract

The Turrum Field is the latest resource to be developed in the prolific offshore Gippsland Basin. Over 50 years of drilling, the basin has produced more than 4 billion barrels of oil and 8 trillion cubic feet of gas from the Latrobe Group. The Turrum Field reservoirs were discovered with the initial Marlin-1 exploration well in 1965, and have been appraised with a number of wells over the following 50 years, yielding interesting results along the way and delineating a set of gas and oil reservoirs with estimated recoverable resources of one trillion cubic feet of gas and approximately 110 million barrels of oil and gas liquids. These reservoirs are now currently being developed via platform drilling off Marlin B, installed in 2013. The Turrum reservoirs are a more challenging resource than the majority of those previously produced in the basin, for both geological and geophysical reasons. Other large fields (such as Marlin, Kingfish and the Central Fields complex) are combination stratigraphic/structural traps at the Top of Latrobe section, which is overlain by the regional seal (the Lakes Entrance Formation). The Turrum reservoirs sit approximately 800mTVD beneath these reservoirs at Marlin, in a lower net-to-gross Palaeocene section contained within a faulted anticlinal trap. These ‘Intra-Latrobe’ reservoirs rely on shales between the reservoir units to seal the hydrocarbon columns. The resource is contained within a succession of lower coastal plain fluvial reservoirs, each pressure-connected laterally across the field but separated vertically leading to separate hydrocarbon-water contacts in each reservoir unit. Because of this depositional environment, the channelized sandstones can vary substantially in extent within the field, which has made their delineation by well control difficult at times. Additionally, there are two main drive mechanisms in these reservoirs which have implications for the development of the field. Geophysically, the reservoirs sit beneath a large gas field (Marlin) with thick coal sections which attenuate the seismic signal, and running across part of the field is a younger palaeochannel filled with high-velocity fill, which can create further imaging and depth conversion issues in the seismic dataset. Significant effort has been put into processing the seismic data to account for these issues, and it is through the integration of a large amount of data that mapping the field and the hydrocarbon contacts has been completed.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015