| This paper mainly focuses on several key problems in the development of LWD azimuthal electromagnetic measurement software,including 3-D forward simulation and 3-D spatial sensitivity function theory,borehole environment and grooved drill collar correction technology,logging data preprocessing method and 1-D multiparameter adaptive regularization Gauss-Newton iterative inversion theory.A software system is developed on Intel Visual Studio Fortran platform,which can be used for numerical simulation of 3-D response in highly deviated wells and horizontal wells,establishment of borehole environment and drill collar correction library and apparent resistivity extraction library,full interval data inversion in post-processing of LWD data,and real-time boundary detection inversion imaging.The software system is verified by the theoretical model and actual logging data,and the key problems in optimization design,post-processing of azimuthal logging data while drilling and geological guidance are solved.At present,the relevant software has been submitted to the Institute of Geology and Geophysics of Chinese Academy of Sciences as the data processing and interpretation software of LWD azimuthal electromagnetic measurement.By using the 3-D finite volume method of coupled potential Helmholtz equation in cylindrical coordinate system,a 3-D numerical simulation algorithm and software for LWD electromagnetic response of a grooved drill collar in arbitrary anisotropic and heterogeneous layers are developed to overcome the problem of low induction number caused by large contrast conductivity and large contrast permeability.The discrete precision of Helmholtz equation of coupled potentials around the drill collar is improved effectively by introducing the extended electromagnetic field boundary condition on the surface of the non-smooth metal grooved drill collar.In addition,PARDISO and OpenMP technique are used to ensure the stability,calculation accuracy and efficiency of numerical results.The effects of metal drill collar,antenna groove and ferrite material in the grooves,eccentricity,relative inclination,formation resistivity and anisotropy coefficient on the response of LWD azimuthal electromagnetic measurement are investigated by using the 3-D numerical simulation software.Based on the perturbation principle and first-order Born approximation theory,a set of spatial sensitivity function(3-D geometric factor)theory is established for the response of LWD azimuthal electromagnetic measurement in anisotropic formation,which can be used to rapidly analyze and evaluate the detection capability of azimuthal electromagnetic tools with metal drill collar and antenna groove.The analysis algorithm and software of LWD azimuthal electromagnetic measurement response and explicit Fréchet derivative are established by using the forward simulation theory of transmission line and multi-parameter perturbation method in horizontal layered TI model.The Fréchet derivatives of attenuation(Att),phase shift(Ps),and each cross component with respect to horizontal conductivity,vertical conductivity and formation interface depth can be calculated simultaneously in the forward simulation process,which provides an important theoretical basis for realizing real-time iterative inversion of azimuthal electromagnetic logging data.On this basis,a multi-parameter adaptive regularized Gauss-Newton iterative inversion method for azimuthal electromagnetic logging data is developed,which can simultaneously determine the horizontal and vertical conductivity of each formation and the position of the layer interface.The electromagnetic response in the cylindrical formation models with different borehole radius,different borehole mud and different formation conductivity is calculated by using forward simulation software.A set of borehole environment and drill collar effect correction library is established,and a correction method is given to eliminate the influence of borehole environment and drill collar effect on the principal component Att and Ps.The effect of borehole mud and drill collar on measurement results is effectively reduced,which provides theoretical basis and technical guarantee for dimensionality reduction processing and inversion imaging of azimuthal electromagnetic logging data.Based on the correction of drill collar effect,a pre-processing method combining apparent resistivity extraction and 0-dimensional three-parameter inversion is developed to obtain the horizontal and vertical conductivity information as quickly as possible.Furthermore,two different data processing methods,full interval data inversion and real-time boundary detection inversion,are established by using the multi-parameter adaptive regularization Gauss-Newton iterative inversion method in layered anisotropic formation,which meet the needs of post-processing of LWD azimuthal electromagnetic data,real-time boundary detection and geological guidance.In order to improve the precision and computational efficiency of real-time boundary detection inversion,a parallel technology of global optimization and OpenMP is developed to invert the formation resistivity and layer boundary around the drill collar in real time using single point logging data.The validity of the inversion algorithm is verified by several theoretical models,and the theoretical synthesis data of inversion results and input data are highly fitted.Besides,the actual data of two groups of well sites are processed,and the inversion results show a good agreement with the geological modeling results. |
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