THE NEW ROYAL OIL FIELD: A CASE HISTORY OF THE DISCOVERY AND APPRAISAL OF A SUBTLE, STRATIGRAPHICALLY TRAPPED HYDROCARBON ACCUMULATION IN THE TRIASSIC SHOWGROUNDS SANDSTONE, SURAT BASIN

Abstract

The New Royal Oil Field is located in a structural embayment on the eastern flank of the Kincora High, western Surat Basin, Queensland. Hydrocarbons have accumulated in the Middle Triassic Showgrounds Sandstone, specifically in a thin basal fluvial unit, interpreted as part of an incised valley fill deposit, that displays excellent reservoir properties but is highly localised in its distribution. The Showgrounds Sandstone overlies either granitic basement or a veneer of Permian clastics including coals. Whereas the Showgrounds Sandstone is an established hydrocarbon bearing reservoir in a number of structural settings elsewhere in the basin, trapping in the New Royal field is primarily stratigraphic.

Since its discovery in November 1995, various exploration techniques and technologies have been applied, including the acquisition of 3D seismic data, in an attempt to understand the trapping mechanism of this field and predict its lateral extent, albeit with mixed success. Twelve wells have now been drilled in the greater New Royal field area, only four of which were successfully completed as oil producers from the basal Showgrounds Sandstone. Production to date totals 1.1 million barrels of oil and reservoir simulation studies indicate that original-oil-in-place was 4.6 million barrels.

This case history serves as a timely reminder that despite all the technology now available to the petroleum geoscientist, serendipity still plays an important role in the discovery and successful appraisal of certain hydrocarbon accumulations in the Surat Basin.