High Resolution Magnetic Anomaly Modelling and its Implication for Petroleum Prospectively on Seram Island, Maluku, Indonesia

Abstract

An airborne magnetic survey was conducted over Seram Island in 2012. The Total Magnetic Intensity ranged from 41,565.7 nT to 41,715.2 nT. High anomaly were observed with a range between 41,665.7 nT and 41,715.2 nT. These anomalies were predominately located in western part of the survey area with some small high frequencies and a long wave length anomalies present in the southeastern part of the island. The high anomalies have been interpreted as Paleozoic rocks of Taunusa Formation. Medium anomaly range from 41,618.9 nT to 41,665.7 nT are present in the east, northeast and west northwest of Seram Island. This magnetic response has been interpreted to reflects the occurence of Mesozoic rocks from Kanikeh Formation. The low magnetic anomalies which range from 41,565.7 nT to 41,618.9 nT are present in the centre and northeast of the island, and reflects the occurence of Jurassic Manusela Formation. Modelling of the high resolution magnetic anomalies, constrained by well data information, confirms the rock stratigraphy while also indicates folds, thrust fault structures and basement fractures being present over the survey area. The occurence of hydrocarbons in the area have been interpreted to be associated with traps in basement fractures. Areas with similar tectonic structure, as interpreted from the high resolution magnetic data, represent a high potential for the presence of further hydrocarbons. The recommended areas are dominated by basement fractures and thrust fault structures. The modelling shows that the source rock, the Jurassic Kanikeh Formation, has thickness of about 2,623.5 metres. The Kanikeh Formation is estimated to have high porosity because it consists of fractured sandstone (Tjokrosaputro et. al., 1993). From the modelling it is also observed that the cap-rock, the Jurassic sedimentary rocks, have thickness reached of about 1,166 metres.