| With the increasing demand for oil and gas resources and the deepening of oil and gas exploration and development,how to correctly evaluate unconventional reservoirs such as thin interactive reservoirs,fractures,and shale gas has become an urgent research topic.As shale,fractures,and thin interactive layers are typical anisotropic reservoirs,it is difficult to obtain formation horizontal resistivity,vertical resistivity,and formation dip angle at the same time using conventional logging techniques.Meaningful industrial oil and gas layers often be underestimated or even missed in reservoir evaluations.The new three-dimensional electromagnetic induction logging technology provides an important means for anisotropic reservoir exploration and evaluation.Three-dimensional electromagnetic induction logging uses triaxial emission and triaxial orthogonal reception measurement methods and it also provides different source distances and tensor electromagnetic data of different frequencies,so that the processing and interpretation of three-dimensional electromagnetic induction logging data often involve the problem of numerical simulation and inversion of three-dimensional electromagnetic field.How to effectively extract the vertical and horizontal conductivity of the formation from the original tensor electromagnetic data logging data,such as intrusion radius,formation dip azimuth,still faces many difficulties.Meanwhile it severely limits the popularization and application of three-dimensional electromagnetic induction logging technology at home and abroad.As this thesis focuses on several key problems encountered in three-dimensional electromagnetic logging,including electromagnetic field analysis algorithms in columnar layered anisotropic media,three-dimensional finite volume algorithm of electric field coupling potential in horizontal layered anisotropic media,borehole environment correction,one-dimensional multi-parameter inversion,comprehensive data processing.In order to match the three-dimensional array electromagnetic induction detection instruments in China,a three-dimensional forward simulation and a set of logging data processing system were developed.First of all,in order to calculate the induced electromotive force on the coaxial tilted transmit and receive coil system,we use the analytical expressions for the electromagnetic field in the frequency wavenumber domain in a cylindrical multilayer anisotropic medium derived from the use of TE wave and TM wave decomposition techniques,acquiring calculation formulas for the emission coefficient,generalized emission coefficient,and amplitude,and then we use spline interpolation to implement the inverse cosine transform to attain the numerical solution of the electromagnetic field in the frequency space domain and the numerical solution of the induced electromotive force on the receiving coil in any direction.Meanwhile the numerical results are used to study and investigate the effects of changes in transmit and receive distance,instrument operating frequency,and anisotropic coefficient on the response of induction logging,providing a theoretical basis for the design of instrument parameters and the verification of three-dimensional numerical simulation results.In order to study and investigate the response of three-dimensional induction logging tools in layered non-uniform arbitrary anisotropic media,we use the electric field coupling potential three-dimensional finite volume algorithm(3D FV)to improve the stability of the numerical results of electromagnetic fields under large contrast conditions.The calculation method of equivalent conductivity in any anisotropic heterogeneous element,the three-dimensional coupling potential Helmhotz equation under the Lebdev staggered grid,and the discrete method of magnetic dipoles in arbitrary directions are established by conducting conductivity standardization techniques.Incomplete LU decomposition(ILU)and the stable double conjugate gradient method(Bi-STABCG)are used to solve the discrete equations.According to the real coil system structure and parameters of the three-dimensional array electromagnetic detection instrument,the response of the three-dimensional electromagnetic induction logging instrument in vertical,deviated and horizontal wells was investigated.On the basis of the above-mentioned forward simulation,in order to apply China's independent research,we develop three-dimensional array electromagnetic detection instruments to explore and evaluate complex oil and gas layers in China as soon as possible.According to the true instrument parameters and instrument response characteristics of the instrument Data processing method for logging data,a relatively complete set of researches was carried out,which includes varieties of methods such as borehole environment correction,apparent conductivity and dip angle extraction,one-dimensional multi-parameter regularized iterative inversion and so on.The related methods have been tested on the theoretical model and have obtained effective results.Finally,based on the above-mentioned theoretical research work,a comprehensive three-dimensional electromagnetic induction logging processing system was established,including raw logging data acquisition input,preprocessing,borehole environment correction,value extraction viewing,and one-dimensional multi-parameter inversion processing.The test and verification of model data and well logging data implicate that the system can effectively obtain formation parameters such as horizontal resistivity,vertical resistivity,formation dip angle,anisotropy and so on.effectively solving the problem of oil and gas evaluation in thin interactive reservoir and anisotropic formation. |
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