THE RENEWED SEARCH FOR OIL AND GAS IN THE BASS BASIN: RESULTS OF YOLLA-2 AND WHITE IBIS-I

Abstract

Boral Energy Resources Ltd and its Joint Venture partners drilled two weUs in the offshore Bass Basin during 1998. Both wells targetted reservoirs in the Upper Cretaceous to Eocene Eastern View Coal Measures (EVCM).

Yolla–2, located in Petroleum Licence T/RL1, appraised sandstones within the EVCM, first established gas bearing in the Yolla structure by the 1985 exploration well Yolla–1, drilled by Amoco. The exploration well White Ibis–1, located in adjacent permit T/18P, was a crestal test on a large basement high updip of the 1967 well Bass-3, drilled by Esso.

Both wells of the 1998 drilling program encountered gas columns in the objective Paleocene to Lower Eocene section of the EVCM (Intra-EVCM). Liquids-rich gas was recovered from these reservoirs in wireline tests. Formation pressure data suggest a thin oil rim is developed in White Ibis–1. Neither well was tested in cased hole though White Ibis–1 was suspended for potential re-entry. Yolla–1 also encountered a gas and oil accumulation at the top of the Eastern View Coal Measures, but this level was not an objective in Yolla–2.

Based on well results and 3D seismic control, a gas resource of between 450–600 BCF OGIP is currently estimated in the Yolla Field. The gas accumulation encountered in White Ibis–1 is estimated at 85 BCF OGIP.

The 1998 drilling campaign has provided encour-agement to the T/RL1 and T/18P Joint Ventures to continue the search for both oil and gas in the Bass Basin. Markets for gas are being pursued in both Tasmania and Victoria and engineering studies are being undertaken in parallel to refine parameters for a potential Yolla Field development. The White Ibis Field may provide a candidate as a satellite to such a development. Depending on the outcomes of these studies, further drilling may occur in 1999 to increase confidence in the reserves base in the Yolla Field, and to further evaluate the exploration potential of T/18P.