Hydrocarbon Prospect of Weda Basin Halmahera Island, Indonesia

Sapiie, Benyamin ¹; Naryanto, Naryanto ²
(1) Geology, Institute of Technology Bandung, Bandung, Indonesia. (2) Exploration, Directorate General of Oil and Gas Indonesia, Jakarta, Indonesia.

The Eastern Indonesia area has been well known as one of the most prolific hydrocarbon potential area in Indonesia since the early exploration history in 1911. This paper will present results of evaluating frontier area for hydrocarbon potential and prospects in the Weda Basin, Halmahera Island.

The Weda Basin is located at offshore the south arm of Halmahera Island, in the Eastern Indonesian province of Maluku. Geologic setting of the island has been studied by many researcher and remains as a subject of discussion today. Large scale westward propagation of Pacific Plate motion along th Sorong Fault Zone occurred since the Tertiary. Continental fragments have been sliced from northern West Papua and transported westward over large distances. The geodynamic evolution of Halmahera and Weda Basin is therefore similar to other basins situated along the Sorong Left Lateral transcurrent Fault Zone.

Proven hydrocarbon occurences have been found in Salawati Basin, which is located to the southeast of Halmahera. Since the early days of exploration in the Salawati Basin workers had recognized that the Salawati Basin ended abruptly at the Sorong Fault to the north and speculated that the “other half” of the basin lay to the north of the Sorong Fault offset by left-lateral movement. Halmahera was considered to be a good candidate for the missing half of the Salawati Basin based on the shape of Weda Bay.

Continental fragments were sliced and transported in large distances westward along this fault. Autochtonous Miocene limestone of Australian affinity was passively carried and formed part of the developing Weda Basin. Their geological history is therefore similar. The tectonic position of the basin during this time occupied a back-arc setting with magmatic arc located in the western arm. Further strike-slip deformation related to the active Sorong Fault Zone and its associated splays which acted as paired fault, may contribute opening of the back-arc basin as a “pull-apart Basin”.

The main potential source rocks are Jurassic and thick Pliocene sequences. 2D basin modeling indicated immature source except for deeper kitchen to the East. The main reservoir targets are Miocene carbonate reefal facies of equivalent Kais Formation. Five The main geological risk factor in the area is source rocks and their maturity. Halmahera block has great exploration potential and opportunity in particular toward the center of Weda Bay targeted Miocene carbonate reefal facies.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.