A Review Of The Reservoir Sands, Patchawarra Formation In The Daralingie Field Area, Southern Cooper Basin, South Australia.
Honours Degree, 1988
University of Adelaide
The Cooper Basin consortium of partners drilled five appraisal wells late in 1987 to evaluate a potential thin oil leg situated beneath the main gas reservoir of the Daralingie Field. This recent drilling activity led SADME to recommend the incorporation of this well data into a local field study to better understand the distribution of both gas and potential oil sandstone reservoirs occurring in the upper portion of the Patchawarra Formation.
Most core taken from reservoir sandstones of facies association 2 were examined together with log suites from 26 wells. The reservoir sands were deposited as simple fining upward sequences in a regime of fluvial to upper deltaic environment of meandering streams.
Five stratigraphic cross sections were then constructed to illustrate the relationship between four designated facies associations. The construction of isopach, sandstone percentage maps together with the reconstructions of the palaeogoegraphy, illustrate the distribution of thick sandstones preserved in mid flank areas of the structure. Facies and isopach relationships of fine to coarse sediments indicate that sporadic structural movements influenced sediment distribution throughout the study area.
Diagenetic studies have determined that quartz grains have been extensively modified by authigenetic silica overgrowths, however coarser grains have not been altered to the same extent as the finer grained sandstones. Porosity and permeability are reduced by illite and quartz overgrowths in the finer grained samples.
The meander belt of coarse sandstones mapped in this study should aid the future development of the Daralingie Field. The facies trend of coarser sandstones and a detailed structure map should be valuable for the planning of downflank wells to test for a possible oil leg.