Study On The Method Of High Resolution Processing For Cross-Dipole Shear Wave Logging

With the gradual development of exploration and exploitation for oil and gas, it is pressing solving the problem of distinguishing thin bed, reevaluating old well logs and seeking neglected oil beds. Therefore, well log must be high resolution processed so as to enhance the accuracy of evaluating thin bed. Cross-dipole array acoustic logging has been applied widely by oil fields at present. Existing array waveforms processing techniques pursue accuracy of each wave component's slowness calculated, while neglect its vertical resolution. In addition, Since it is difficult to build model, the applied effect of existing high resolution processing methods for conventional sonic log is not completely satisfactory though it has acquired some effects. Based on the theory of geophysics and digital signals processing, the high resolution processing method of maximum entropy and cross power spectrum phase combined with multiple-shot method has been presented for the wavesonic well logging. The arrival of components must been picked for the method of maximum entropy and cross power spectrum phase. For the dipole waveform, it calculates the product of multiplying energy ratio between the long window and the short window by the square of the amplitude envelope of waveforms to pick the S-Wave arrival. First, it calculates the slowness between the near recerver and the far recerver by using of the STC method. Then, it calculates the main frequencies of the near waveform and the far waveform by using of the maxium entropy method, and regards the average the main frequencies of the near waveform and the far waveform as the main frequency of the component, and using the surplus phase processed by use of cross power spectrum phase method compensates the slowness calculated by using of the STC method, also obtains the slowness of the shortest subarrays (0.152m). At last, it averages all the slowness of the same depth interval formation spanned by the shortest common-source subarrays and common-receiver subarrays and obtains the higher resolution slowness Apply the technique to array acoustic logging data in Daqing Oil Field, and compare its results with the results precessed by express. It shows that the method has the higher resolution, also ensures the accuracy of the slowness.