Permian Deposition in the Eastern Nappamerri Trough, Cooper Basin

Abstract

Prior to 2012, petroleum wells in the eastern portion of the Nappamerri Trough (Cooper Basin) were scarce with only a handful of wells drilled in an area of approximately 5,000 square kilometers. Recently, the Nappamerri Trough has become the focus for an extensive shale gas and basin centered gas exploration campaign. Sparse regional 2D seismic lines through the trough were thought to be adequate for developing a regional structural model and for estimating distribution and thicknesses of the Permian strata. Between 2012 and 2014, six exploration wells were drilled in the ATP855 permit which covers the deepest portion of the trough. Wells drilled in this area intersected formations that were generally thicker than predicted. The increased thickness coupled with apparent lithostratigraphic changes from east to west resulted in stratigraphic correlations having a high degree of uncertainty. Challenging drilling conditions due to the high geothermal gradient and overpressure in the trough limited data acquisition in some wells. The lack of log data in some wells exacerbated the problems of correlating the Permian formations. Although used routinely in other basins around the world, Chemostratigraphic techniques were new to the Cooper Basin. Chemostratigraphy was used in ATP855 to not only assist in defining the standard lithostratigraphic correlations used basin-wide, but to also aid in the sub-division of the Permian formations. The chemostratigraphy was integrated with image log derived structural zones and cuttings analysis to better define the stratigraphic correlation scheme for the eastern Nappamerri Trough.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015