Seismic acquisition design for Laoshan uplift of the South Yellow Sea

The Mesozoic-Paleozoic marine carbonate deposits on the Laoshan uplift of South Yellow Sea are critically important for petroleum exploration. However, the seismic reflection of the Mesozoic-Paleozoic strata has the problems of weak energy and low S/N ratio, owing to the facts that water is relatively shallow, the interface between the terrestrial Cenozoic and the marine Mesozoic is too strong as a seismic impedance reflector, the structure of Mesozoic-Paleozoic strata is uniform with little velocity and density difference, and the thickness of Mesozoic- Paleozoic strata is too large. In the seismic survey of the project, measures were taken to enhance the seismic reflection wave's energy and increase the S/N ratio of the Mesozoic-Paleozoic strata, with specific design on both seismic source and acquisition parameters. A 6390in³ air gun source with strong energy and low frequency, and with both single level mode and multi-level mode was designed. Two streamer depth candidates (16m and 20m) were chosen. The streamer length was designed to be 7200m. 4 acquisition tests were conducted and the 6390in³ in single level mode with depth of 10m and streamer depth of 16m were settled as the final acquisition parameters. A single source-6 steamer is used to increase the spatial sampling. All these formed a seismic acquisition design with high folds, rich low frequency and strong energy. Compared to the previous seismic data, the seismic data of this survey had an overall improvement in quality for the Mesozoic-Paleozoic strata, as the seismic reflection energy of the Mesozoic-Paleozoic was enhanced and the S/N ratio increased. The breakthrough in seismic data quality will lay a solid foundation for the next drilling site determination.