Magnetotelluric and Gravity Imaging of Sedimentary Basin in Indonesia: A Case Study

Abstract:

To find out the possibility of the existence of sedimentary basin is the survey area has been carried out by applying magnetotelluric (MT) and gravity method. In the MT method, naturally existing electromagnetic fields are used to study the electrical substructure of the earth. We analyzed electrical properties of rock and gravity anomaly derived from 75 km profile of MT and gravity data. Bouguer anomaly also has been analyzed to investigate low anomaly zone. Both MT and Gravity results are match and give us a possibility of the existence of sedimentary basin. Residual anomaly shows low value in two areas which are indicate as sedimentary basin separated by medium-to-high anomaly value. MT shows conductive anomaly (less than 10 ohm.m) surrounding by resistive layer (11-20 ohm.m) then overlaying higher resistivity layer 21-120 ohm.m and 121-180 ohm.m, respectively. Initial interpretation suggest that the Oligo-miocene sediment are imaged as a conductive layer overlaying Eocene and the resistive Crestasious basement. We can concluded that MT method can be applied for detect sedimentary basin existence in hydrocarbon exploration as preliminary survey combining with gravity method. Those method are typically used in frontier areas to do reconnaissance exploration, to look for new basins, and to investigate large areas that might be prospective for doing more detailed.