3D OBN Seismic Acquisition with Undershooting Method for Fold Coverage Data Optimization at X Field, Indonesia

One of the key challenges in conducting seismic surveys in the X Field, located in the transitional zone of Papua, is the presence of shallow waters, with depths ranging from 1 to 4 meters. These shallow areas prevent gunboats from passing through, as there is a risk of grounding. To overcome this, several shot points were offset using deviation surveys. Shot points in shallow waters were shifted to areas with depths greater than 4 meters where the gunboat could safely operate, while the receiver points remained at their original positions. This resulted in shot and receiver points not being aligned along the same acquisition line.

During deviation, the gunboat turns and simultaneously performs shooting. This method is known as the undershoot method, and it has proven to be operationally effective, especially compared to using dynamite sources with catamaran drilling in shallow areas. Data obtained from this method shows that the Common Depth Point (CDP) positions, even after deviation, remain within the target prospect area, ensuring no loss of subsurface information. Moreover, the fold coverage achieved aligns with the planned acquisition parameters, maintaining a consistent 180-fold, supporting high-quality seismic imaging.