THE TARBAT-IPUNDU OIL FIELD, A CASE STUDY IN IDENTIFYING BYPASSED OIL

Abstract

Since 1995 the Tarbat-Ipundu Field has developed from a marginal 200 BOPD (31.8 kL/d) field with perceived limited growth potential to a developing resource with production up to 3,000 BOPD (476.9 kL/d). This increase was achieved through the efforts of a dedicated multidisciplinary team and an aggressive 'fit for purpose' drilling and evaluation program.

The Tarbat-Ipundu Field is located in PL 52 of ATP 299P in southwestern Queensland, approximately 115 km to the northeast of the Jackson Oil Field. The field was discovered by Hartogen Energy Ltd in 1986 with the drilling of Ipundu 1 which came on-line at 100 BOPD (15.9 kL/d) from the Wyandra Sandstone and the Murta Member. The discovery well was followed by the drilling of Tarbat-1 in 1988 on a subculmination to the north. Tarbat-1 encountered oil in the Wyandra Sandstone but watered out after producing 17 KSTB (2,702 kL) of oil. During 1991 a further four wells were drilled in the Ipundu Field by the then operator, Ampolex Pty Ltd. Two of these wells were plugged and abandoned. In January 1994 the field was producing at 220 BOPD (34.9 kL/d) after a total production of 350 KSTB.

The Santos Group acquired a majority interest and Operatorship of the Tarbat-Ipundu Field in 1994. An integrated geological and engineering evaluation of Tarbat-1, incorporating experience gained in other parts of the Eromanga Basin, indicated the potential for bypassed oil in the Hutton Sandstone. Similarly, additional potential was recognised in the Wyandra Sandstone and Murta Member in the Tarbat-Ipundu wells. To evaluate this potential Tarbat-2 was drilled in August 1995 at a location 315 m to the northwest of Tarbat-1. Drill stem tests in Tarbat-2 resulted in flows of 2,037 BOPD (323.8 kL/d) from a 26 m gross hydrocarbon column in the Hutton Sandstone and 770 BOPD (122.4 kL/d) from a 14 m gross hydrocarbon column in the Wyandra Sandstone.

An aggressive appraisal and development program followed the drilling of Tarbat-2 which has resulted in the drilling of an additional 25 wells. Proved and Probable Oil in Place estimates have increased from 5.2 MMSTB (0.826 ML) in 1994 to 44.2 MMSTB (7.02 ML) in 1997. As at June 1997 the field produces oil from the Wyandra

Sandstone, Murta Member and Hutton Sandstone of the Eromanga Basin. A combined oil offtake of up to 3,000 BOPD (476.9 kL/d) has been achieved from the field. Continued field development is planned for 1998.

The successful 're-discovery' of the Tarbat-Ipundu Field illustrates the potential benefit of a systematic review and integration of all existing data via a multidisciplinary team. The increasing cost of new data acquisition makes it imperative that the existing data is thoroughly evaluated prior to the investment of further exploration capital. The Tarbat-Ipundu Field demonstrates the potential to add significant new reserves from focussed targeting and evaluation of potential bypassed hydrocarbon accumulations.