Publication Name: Second South-Eastern Australia Oil Exploration Symposium - Technical Papers
Authors: C.I. Sharpe and R.J.W. McLaughlin
Date Published: December 1986
Number of Pages: 24
Reference Type: Book Section
Abstract:
Hydrocarbons may be present in groundwaters above a hydrocarbon reservoir and several factors have been identified that influence the extent of hydrocarbon seepage through the intervening cap rock. The analysis of trace amounts of heavy fraction hydrocarbons dissolved in an overlying aquifer can be used as a exploration tool. This procedure is discussed in the paper.Liquid-liquid extraction and XAD-2 (organic polymer resins) were used to extract the trace amounts of hydrocarbons from bore waters. The organics were then concentrated and analysed using a gas-liquid chromatograph (GLC).
A case study was carried out in exploration permit PEL 265 in north-western New South Wales. The permit was subdivided into two areas, 'potentially prospective' and 'barren', principally on the basis of visible hydrocarbons in the bore waters. These two zones were confirmed by the GLC traces of the hydrocarbons
obtained from the waters.
GLC traces from the Moomba gas field and Gidgealpa oil field, used as controls, show the method not only able to distinguish between areas that are prospective for hydrocarbons and those that are not, but also between gas prone and oil prone accumulations. Alkane ratios suggest hydrocarbons in PEL 265 are sourced from mature, terrestrial kerogens deposited under oxidizing conditions.
The method is able to provide an inexpensive and rapid appraisal of a sedimentary basin prior to the high cost of seismic surveys and exploratory drilling.