Sedimentology And Reservoir Potential Of The Mid-Cambrian Trainor Hill Sandstone, Eastern Officer Basin.
Rudd, Damion Scott
Honours Degree, 1995
University of Adelaide
The Mid to Late Cambrian Trainor Hill Sandstone, is one of a number of prospective reservoir units within the Officer Basin in northwestern South Australia. Detailed core analysis, and petrological studies have indicated that the unit is a shallow marine to deltaic sandstone, despite previous interpretations referring to the Trainor Hill Sandstone as a fluvial to fluvio-deltaic sandstone. The Marla area is dominated by tidal flat shales to offshore barrier bars, whilst the Ungoolya Area is dominated by tidally influenced channel systems and classical deltaic facies.
Intraformational well correlations within the Officer Basin are considered extremely difficult given the lack of uniformity between logging companies and their respective logging units and the distance between many of the wells previously drilled. These pose as substantial problems, particularly in the delineation of prospective reservoir units.
Study of the sandstone diagenesis of the unit has indicated that many of the coarser grained sediments have been reworked from older sandstone units, further down the stratigraphic column, as many of the grains exhibit texturally mature secondary quartz and feldspar overgrowths. This study has also indicated the presence of three cement phases which are believed to have been in place prior to compaction. These cements are quartz, pyrite, and calcite, with the pyrite cement inferred to be hydrothermally associated.
The reservoir potential of the Trainor Hill Sandstone is quite substantial given measured porosities and permeabilities of up to 24.9% and 5429md respectively. These values are quite comparable with those of current Australian producing fields. The majority of the porosity is generally intergranular with very minor intragranular porosity after carbonates.
The potential of the Trainor Hill Sandstone as an effective reservoir is excellent although the possibility of detecting and deliniating particular sand bodies is limited considering the spatial distribution and quality of data currently at hand. Further investigation into the basin would prove beneficial providing data quality is improved.