Maturation Timing And Migration Pathways In The Battunga Trough: Exploration Licence Co98-J, Southern Cooper Basin.
Honours Degree, 2000
University of Adelaide
A burial history and diagenetic study of the Battunga Trough and area to the south within the southern Cooper Basin, northeastern South Australia, was carried out to constrain the timing of thermal maturation and hydrocarbon migration. The results encourage further exploration.
Open file well data, including vitrinite measurements, bottom hole temperatures, geothermal gradients, petrophysical logs, and drill core were synthesised to build a history of source rock maturation, hydrocarbon generation and migration in the Battunga Trough into the "Mulga" exploration licence block CO98-J. Only seven wells have sufficient data for the burial history study, and available drill core restricted the diagenetic study to five wells. Three types of thermal/burial history models were constructed.
The majority of wells studied have Permian successions that have reached at least early oil generation maturity, and maturity increases into the Battunga Trough. The thermal history modelling suggests that the southern Cooper Basin has been subjected to very high heat flows prior to 105 Ma when a rapid cooling event began. This study also shows that heat flow has increased rapidly in recent times.
Previous studies of diagenetic history in the southern Cooper Basin have shown three phases of siderite cement, three of quartz cement and the complete alteration of feldspars. The current study indicates the area south of the Battunga Trough has only one phase of quartz cement, two of siderite and only partial dissolution of feldspars.
The diagenetic study used image analysis of thin sections to calculate porosity (percent). This analysis showed highly variable porosities throughout the study area ranging from 0 to 20 percent. In many samples, however, a large proportion of this porosity is in the form of microporosity.
An understanding of the timing of maximum oil generation and the timing of diagenetic events indicates that current day reservoir porosities in the Patchawarra Formation of the southern Cooper Basin have not changed much, barring any recent dissolution events, from the time of peak hydrocarbon generation (up until 105 Ma).