Acquisition and Processing Challenges for Very Large Offset 3D VSP in the Arabian Gulf, Saudi Arabia

In 2009, Saudi Aramco acquired three large 3D VSP surveys in the Arabian Gulf, Saudi Arabia. These surveys were not only the first of their kind in Saudi Aramco, but each was also the largest, single well offshore 3D VSP worldwide. The primary objective of the survey was to improve the vertical and lateral resolution of signals from the sand stringers near and away from the well to properly place multi-lateral horizontal wells. A 100-level 3–component geophone tool was deployed in each well over a depth range of 1600 to 6600 feet. Each survey consisted of 32,000 shot points and 9 million traces. It was designed to optimize the subsurface coverage of mode-converted P-to-SV waves (C-waves) at the target using a maximum offset to depth ratio of 2.5. The surveys were completed in the shortest possible time to minimize drilling rig time. The objectives, acquisition design, QC procedures and logistical planning are described, which led to three successful offshore 3D VSPs.