DETECTING OVERPRESSURE ZONES USING MODEL-BASED SEISMIC INVERSION: A CASE STUDY FROM SRIKAIL-01 WELL, SRIKAIL GAS FIELD, BANGLADESH

An overpressure zone is critical in petroleum exploration drilling, leading to potentially dangerous blowouts and other drilling-related hazards. Yet, it often contains significant hydrocarbon reserves in sedimentary basins. This research aims to determine the possible overpressure zones in the Srikail Well-1 of the Srikail Gas Field. The acoustic impedance responses of 2D seismic data for the Srikail Well-1 and its well log responses were examined to find probable overpressure zones at the Srikail Well-1. Seismic inversion is a crucial method in this study for identifying and understanding overpressure zones. Hence, the process involved extracting wavelets, conducting well correlation, determining and picking horizons, followed by model-based seismic inversion, and calibrating pressure to well logs and seismic data using Kerry 2D post-stack seismic data to derive acoustic impedance, a crucial indicator for the presence of potential overpressure. Well-log responses provided evidence for this analysis. The density and sonic log responses of the Srikail-1 well were carefully evaluated. The intervals indicating possible overpressure locations, as identified through a seismic acoustic impedance, exhibited reasonable consistency with the well-log data. The Srikail-1 well does not have enough well-log information, such as density, but it affects the changing trend of well logs. The sonic logs solely follow the rule of an overpressure zone. A cut-off frequency between 4 and 8 Hz was used to build the Srikail-01 well initial model, and the wavelet was created using well logs and seismic data. Very low acoustic impedance values are observed on the model-based inversion map of the Srikail-01 well at a depth range of approximately 3548.58m in the subsurface corresponding to the overpressure zone. Conversely, the identified overpressure zone has encountered the Bhuban formation. Bangladesh’s hydrocarbon reserves are depleting due to high consumption, but unexplored areas and overpressure zones offer untapped potential. Revisiting known structures with robust methods can help to address rising demand.