The Relationship Between Core-Derived Oil Saturations In Live And Residual Columns Of The North West Shelf, Australia.
Murphy, Ian R
Honours Degree, 1998
University of Adelaide
This study is aimed at finding the relationship between core- derived oil saturations in live and residual columns in order to provide more accurate estimates of recovery volumes. This study focussed on the Mardie Greensand member of the Muderong Shale, but investigated other reservoir units in the Northern Carnarvon Basin as well. The study is based on an analysis of core-plugs from 85 wells and some complementary hydrocarbon column data that are distributed throughout the North West Shelf.
The study addresses the relationship between the core-derived porosity and oil saturation, through the statistical analysis of the core-saturations, permeabilities and porosities. The study also addresses the relationship between the height of gas columns and the thickness of the residual oil columns in a number of wells.
Saturation results may be influenced by the manner in which the cores were cut, transported and analysed. There are a number of ways in which the samples can be rendered unrepresentative by poor drilling techniques or by poor handling.
The relationship between the permeability and porosity for the core-plugs was identified as a good method of reservoir characterisation. The relationship between the porosity and permeability of the sample has a greater chance of remaining representative than other quantities such as core-oil saturation that may be corrupted through flushing or stripping.
The North West Shelf was divided into local areas to appreciate the broad range of reservoir lithologies, depth and diverse oil chemistries and saturations. The use of the relationship between the gas and residual oil column height provided a valuable insight into the charge and leak history of the reservoirs; possibly one of the most important contributors to the formation of a residual column.
The conclusion from this study suggests mechanisms that govern the creation of a residual oil column.