High Resolution Seismic Imaging and Fault Detection using Walkabove and Rig VSPs in Ras Budran and Ras Fanar Fields in The Gulf of Suez

摘要

The Gulf of Suez is well known for complex geological setting due to salt plays, complex faulting, high dips etc. Surface seismic is typically affected by strong multiple activity and heavy energy losses resulting in low resolution seismic, making the seismic imaging a big challenge for Geophysicists. Consequently, the geophysicists face problems while planning and drilling new development wells due to unexpected events i.e. faults, missing targets etc. Suez Oil Company conducted standard rigside borehole seismic surveys to address some of the seismic issues in their concessions. Such surveys also resulted in uncertainties in time-depth relation and poor imaging even in wells with low inclination. The paper presents case studies where VSP surveys were conducted in Zero Offset geometry in vertical and Walkabove in low and highly deviated well sections in Ras Budran and Ras Fanar offshore fields. VSP programs were designed after pre-survey modeling simulating different scenarios to meet the objectives as well as ensuring safety and cost effectiveness. Accurate time-depth relations were derived in wells with low as well as high inclination. Three-component full waveform data were processed leading to high resolution 2D images beneath the deviated well trajectories. The results helped in reducing surface seismic uncertainties for shallow as well as deep targets, and refining interpretation. Additionally, VSP image helped to control the structural boundary as new faults were delineated successfully, which were not detected in low resolution 3D surface seismic.