Successful fluid discrimination in tight, overpressured reservoirs using AVO inversion

In 1995, the Longtom-1/STl wildcat well - drilled in the northern part of the offshore Gippsland Basin (Figure 1) - encountered dry gas in tight, overpressured sandstones. The reservoir is situated in the Admiral Formation of the Emperor Subgroup. The Longtom-2/ST1 exploration well confirmed significant vertical and lateral extension of these prospective gas sands (see Figure 2) in 2004, and also provided very encouraging production test and core data. The recent Longtom-3 and -4 wells have demonstrated the viability of this new play by confirming significant lateral continuity of the thicker gas sands and demonstrating high gas flow rates. A multi-disciplinary and interactive approach, guided by seismic inversion techniques and real-time petrophysical data, resulted in the successful planning and execution of the Longtom-3 (for more information see Lanigan et al., 2007) and subsequently the Longtom-4 drilling and evaluation program.