Research on the Construction Location Deviation of Seismic Acquisition Physical Points in Loess Plateau
Seismic exploration has advanced to the stage of precise structural characterization of underground unconventional oil and gas reservoirs and fine imaging of reservoir lithology,and the seismic wave sampling interval in seismic acquisition parameters has entered the era of 1 ms.All these put forward more accurate requirements for the construction of physical points in seismic data ac-quisition,especially the vertical deviation of physical points has a very serious impact on the sampling interval of seismic waves,and the provisions on the deviation of physical points in the technical specifications for geophysical exploration acquisition are rough and broad.With the seismic exploration and construction of Loess Tableland as an example,through detailed data calculation and analysis research,it is shown that:①When the horizontal deviation of the physical point construction location is 4 m,compared with the nor-mal physical point construction,the travel time difference of the seismic wave Δt is 2 μs.This deviation is negligible for the require-ment of seismic wave sampling interval of 1 ms.②According to the low-speed layer speed of 500 m/s on the loess tableland,the seis-mic wave travel time difference between the vertical physical point construction position and the normal physical point construction position is 0.000 4 s,that is,0.4 ms,under the condition of 0.2 m deviation.The effect of the 0.4 ms round-trip travel time of the seismic wave generated by this 0.2 m vertical construction deviation is not negligible for the current 1ms sampling interval of seismic exploration.The research results include a table of the influence difference of seismic exploration physical point construction devia-tion on seismic wave travel,and six targeted control measures are proposed to improve the quality of seismic exploration data collec-tion and obtain high quality seismic exploration results.
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