Banda Arc is a result of the interactions of Eurasian, Pacific, and Indo-Australian Plates. The southern part of Banda Arc is a result of interaction between Eurasian and Indo-Australian Plate. Sahul Platform and Ashmore Platform, separated by Sahul Syncline, are a few of major tectonic elements in Southern Banda Arc system. Banli-1 well is an exploration well located onshore in the southern edge of West Timor and was drilled in 1993. The result of the pressure data acquisition while drilling shows that there is overpressure interval in Banli-1 well, which indicates an uplifting event of Timor Island. Based on data integration between well markers and depth structure map of Jurassic interval, the present condition of Timor Island is 2,296 feet higher than Ashmore Platform.
This study was conducted to estimate the position of Timor Island prior the uplifting compared to Ashmore Platform, and also to predict the amount of uplifting in Timor Island. The amount of uplifting will be compared with the Ashmore Platform as an elevation reference. Identification of the amount of uplifting happened in Timor Island can be done using pressure data in Banli-1 well. Minimum amount of uplifting occurs at Timor Island is the difference between the depth of the pressure data and curve of hydrostatic pressure. With this method, the minimum amount of uplifting can be identified at 1,813 feet compared to present condition.
It can be concluded that the well pressure data in Banli-1 well can be used to explain the geology in the South Banda arc, and to calculate the amount of uplifting of Timor Island. Based on the calculation using the well pressure data, the position of the Timor Island prior the uplifting is already higher than Ashmore Platform.
Authors : M. N. Juliansyah, R. D. Putrohari