Velocity Model Uncertainty Estimation in Area with No Well Calibration in Central Oman

Accurate depth conversion is a critical component in hydrocarbon exploration, as it directly influences the success of Trap definition and subsequently volume and first well exploration placement. This process involves converting seismic data recorded in time domain into depth domain using velocity model. Hence, the reliability of depth conversion is highly impacted by the velocity model uncertainty and the availability of well data. Small changes or uncertainties in the velocity model can significantly impact the accuracy of converting seismic data from time to depth. Conversion uncertainty increases with target depth; as the target becomes deeper, the associated uncertainty tends to grow. In addition, implementing depth conversion in regions characterized by low relief structure is highly sensitive to the accuracy of the velocity model. Due to the subtle vertical separations inherent in such settings. Therefore, developing a geologically consistent and data-constrained velocity model is critical to minimize uncertainty in depth conversion and ensure accurate assessments of volume estimation to ensure success in well placement. This paper demonstrates a case study from an area in central Oman, where the subsurface team attempted to build a robust velocity model estimation approach by calibrating a regional velocity model with Pre-stack Depth Migration (PSDM) velocity model. A key challenge in this project is lack of well data in area of interest as this work was implemented to plan the first well in the area. The primary target of this well is at depths of more than 5 km hence the uncertainty is higher The main aim is to address the velocity model uncertainty by utilizing both the localized seismic Pre-stack Depth Migration (PSDM) velocity with regional velocity model trends generated using available wells from nearby fields. The team evaluated and compared both models and assured their validity to be used for structure map depth conversion. Hence, this outcome feeds into the volumetric estimation of subsurface trapped hydrocarbons. While both models confirm the presence of the trap, some variation between the models observed and was used to estimate uncertainty in volume calculation