Study On Low Frequency Vibroseis Seismic Exploration Technology For Deep Carbonate Rocks

There are broad exploration fields in the great desert area of Tarim Basin.The main exploration target is the study of deep Ordovician carbonatite fault solution.In recent years,"two widths and one height"(wide azimuth observation,broadband excitation and high density)3D seismic exploration technology has developed rapidly,which provides a solution for the evaluation of ultra deep complex oil and gas reservoirs and structural imaging in complex areas.At the same time,the traditional explosive excitation method is more and more limited by cost and environmental protection under the condition of high-density acquisition.The continuous progress of low-frequency vibrator high-efficiency acquisition technology makes it a reality to promote it in the large desert area.Limited by the strong absorption attenuation caused by the loose surface conditions in the mobile desert area and the exploration target of ultra-deep reservoir,the original data excited by vibrator has the characteristics of narrow frequency band,serious development of near shot point scattered surface wave and linear noise,weak signal-to-noise ratio of deep energy,which restricts the improvement of profile quality and the completion of exploration target.How to improve the acquisition and processing quality of low-frequency vibrator data has become the most urgent task to solve the large-scale application of vibrator in desert area.Based on the 3D seismic exploration of low-frequency vibrator in Tazhong area,this paper puts forward the observation system scheme of small panel,high coverage and long arrangement,and the acquisition parameters of linear frequency increasing excitation and combined reception.In terms of processing,Yu filtering technology is introduced to pick up the first break information with high precision and optimize it.Combined with the frequency division and zoning strategy,the "black triangle" strong energy noise is effectively suppressed.Aiming at the seismic data excited by vibroseis in desert area,the technical process of coherent noise suppression,wavelet processing and high-precision prestack depth migration modeling are proposed.Finally,a set of acquisition and processing technology suitable for low-frequency vibrator exploration in large desert area is summarized.The application results of practical data show that this set of technical process can effectively improve the accuracy of first break picking and the effect of subsequent tomographic static correction.The wavelet processing technology process effectively eliminates the spatial inconsistency of seismic wavelet excited and received by vibrator in large desert area.The frequency division and zoning strategy can effectively suppress the strong energy near shot points,improve the quality of single shot data,and finally effectively improve the quality of prestack depth migration data and beaded imaging.