Research On High-precison Seismic Exploration Acquisition Methods In Paralic Zone

For the special geologic environment of paralic zone, seismic exploration of this area has its unique characteristics, so the conventional practice cannot satisfy the further development of high-precision seismic exploration in these areas.In this paper special measurements are presented to solve the difficult problems in paralic zone, such as slow S/N, low resolution and noise, and great progress were made in seismic acquisition of paralic zone.Conventional dynamite source is not suitable to use in paralic zone, so we developed new dynamite sources, such as lag-stacking vertical source, common-center focusing source, ground rolls source, shear wave source, and so on. Research has been made on the airgun principle and its testing strategy, then we simulated the wavelets in both near field and far field of the airgun source on the Ziolkowski model basis, and the analysis on its energy and P/R at different depths is given.In order to improve the quality of recording, the mechanism of geophones is discussed, and different types of geophone coupling devices are designed based on the paralic environment and surface contraction. Testing results have proved that these geophones are effective. We find that the resolution, dynamic ranges are both improved. Moreover, the coupling capability is enhanced and noise is attenuated to certain extent, In order to record with receivers based on the same principle, research on the marsh hydrophone is involved, which include the principle, design, sample testing. Surface structure surveying technique is developed to survey the surface-structure. Because the receivers will swift with water flow, which introduce improper stack, secondary positioning is introduced, which, in principle, is the combination of first break positioning and sonar positioning.With these efforts, a set of seismic exploration strategy is formed, which is suitable to the paralic zone of Bohai gulf.