Ground displacement analysis in the Sarulla geothermal field using Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) method

Abstract

The Sarulla geothermal field is aggressively developed in Indonesia, reaching 330 MW in two consecutive years. Furthermore, the field is situated along the active Great Sumatra Fault. This condition has the potential to induce surface deformation phenomena attributed to exploitation activities, tectonic activities, or a combination of both. The Persistent Scatterer-Interferometric Synthetic Aperture Radar (PS-InSAR) method is a multi-temporal Synthetic Aperture Radar (SAR) image processing technique employed to detect surface deformations with millimeter-level accuracy. PS-InSAR has been applied in this paper over the Sarulla geothermal field, which comprises two exploited prospects (Silangkitang and Namora-I-Langit) and two unexploited prospects (Donotasik and Sibualbuali). The objective of this paper is to analyze the characteristics of ground displacement over the exploited and unexploited geothermal areas. Multi-temporal images of SENTINEL-1A with ascending and descending orbital modes from 2017 to 2021 were processed using PS-InSAR method. A series of interferograms from the selected primary image were paired with secondary images using SNAP program and Python-based program snap2stamps. The generated interferograms were used as input for the StaMPS program to obtain the persistent scatterers as the best coherent points. Ground displacement towards the satellite line of sight was observed within those two exploited geothermal areas adjacent to the production and injection zones. The descending images resulted in more significant PS points than ascending images. The exploited geothermal area shows a clustered pattern of PS points with a significant rate of ground displacement, whereas the unexploited area suggests a wide dispersion of PS points with a slight amount of displacement rate. Additionally, the detected ground displacement that occurred adjacent to the Great Sumatran Fault may indicate the active movement of the fault.