Model-based dispersive processing of borehole dipole wave data using an equivalent-tool theory

We have developed a model-based processing technique for borehole dipole S-wave logging data to estimate formation shear slowness from the data. During dipole acoustic logging, the presence of the logging tool can significantly affect the dispersion characteristics of flexural waves. Therefore, modeling the effects of the tool is essential for model-based processing. We have determined that an equivalent-tool theory using only two parameters, tool radius, and modulus, can adequately model the flexural-wave-dispersion characteristics. We used this theory, together with a calibration procedure, to determine the tool parameters to formulate an inversion method for the logging data processing. Our use of the equivalent tool theory played an important role in fitting the theoretical dispersion curve to the actual flexural-wavedispersion data, enabling fast processing of the field acoustic data. An advantage of this model-based method is its prediction power, which, in the absence of low-frequency dispersion data, allows for predicting formation shear slowness from the low-frequency limit of the model-fitted dispersion curve. We have also developed an application procedure of the method for field-data processing and demonstrated its effectiveness in the dispersion correction using field acoustic data from fast and slow formations.

我们开发了一种基于模型的钻孔偶极子S波测井数据处理技术，用于从数据中估算地层的横波慢度。在偶极子声波测井过程中，测井仪器的存在会显著影响弯曲波的频散特性。因此，对仪器的影响进行建模对于基于模型的处理至关重要。我们确定，仅使用两个参数（仪器半径和模量）的等效仪器理论能够充分模拟弯曲波的频散特性。我们利用这一理论以及一种校准程序来确定仪器参数，从而制定了一种用于测井数据处理的反演方法。我们使用等效仪器理论在将理论频散曲线与实际弯曲波频散数据拟合方面起到了重要作用，使得能够快速处理现场声波数据。这种基于模型的方法的一个优势在于其预测能力，在没有低频频散数据的情况下，它能够从模型拟合频散曲线的低频极限预测地层的横波慢度。我们还开发了该方法用于现场数据处理的应用程序，并利用来自快地层和慢地层的现场声波数据证明了其在频散校正方面的有效性。