BAYU/UNDAN GAS-CONDENSATE DISCOVERY: WESTERN TIMOR GAP ZONE OF COOPERATION, AREA A.

Abstract

The Bayu/Undan Gas-Condensate Field straddles the boundary between the ZOCA 91-12 and ZOCA 91-13 PSC areas, within the Timor Gap Zone of Cooperation Area A (ZOCA). The field is located approximately 450 km north­west of Darwin, NT, and 350 km east-southeast of Kupang, Timor. The closure is the culmination of the Flamingo High, a major structural element within the northern Bonaparte Basin. This structure has been viewed as having significant hydrocarbon potential since Flamingo-1 recovered gas from Berriasian sandstones in 1971.

The discovery well, Bayu-1, was drilled by the ZOCA 91-13 contract operator, Phillips Petroleum Company ZOC, in early 1995. Bayu-1 intersected a gross 155m gas-condensate column within Middle Jurassic sandstones at a depth of 2,954.5 mSS. The ZOCA 91-12 joint venture then drilled Undan-1,10 km northwest of Bayu-1, on a separate culmination within the closure defined by the Bayu-1 gas-water contact. Undan-1 and subsequent wells have confirmed the existence of one large gas-conden­sate field, with a most likely areal extent of over 160 km2.

The sandstone reservoir consists of late Oxfordian to Callovian shallow marine, deltaic to shoreface, coarsen­ing upward parasequences, overlying Callovian to Bajocian marginal marine to coastal plain sediments. The trap is an east-west oriented horst block bounded by en-echelon normal faults to the north and south, with dip closure to the east and west. Seal is provided by Tithonian to Barremian marine claystones. A likely hydrocarbon source is contained within the Barremian to Callovian interval, some of which are mature for condensate and wet gas expulsion in the southern Sahul Syncline and Malita Graben.