Shallow Hazard Assessment for Pre-Drilling Evaluations Using Seismic Attributes in Sepinggan Field

Abstract Shallow hazard analysis is crucial in pre-drilling evaluations, especially in prospective offshore fields. Overlooking hazards in shallow sections may result in drilling complications such as borehole rupture due to gas pockets and borehole losses caused by the presence of coal seams and carbonates. These hazards could not only disrupt operations but also lead to catastrophic disasters, including instant rig blowouts, underground fracturing, loss of materials, environmental issues, and even loss of life. Despite the installation of a diverter and a Blow-Out Preventer (BOP), a shallow hazards assessment is still necessary to avoid such events. Our study explores the potential of shallow hazards by employing 2D high-resolution seismic data from the Sepinggan Field. The Sepinggan Field is located offshore of East Kalimantan and is identified as an inner shelf with deltaic influence. Coal seams and sand gas layers in this field contributed to gas peaks. We applied the RMS amplitude and the sweetness seismic attributes to reveal amplitude anomalies related to shallow hazards. RMS amplitude is a reliable attribute that highlights high amplitude values, supporting the identification of bright spots and amplitude anomalies. Additionally, sweetness attributes effectively identify the area of interest in the seismic section by characterizing the combination of high amplitude and low frequency. The findings were illustrated by an average energy map and a maximum amplitude map. Those amplitude-based attributes help us emphasize gas zones and lateral continuity of gas-charged sediments. The analysis results were validated using total gas data and drilling events. These insights and evaluations provide valuable insight for well-drilling planning to anticipate hazards.