Forward Modeling For Three-component Induction Logging Using 3D Finite Difference Method

It is estimated that about 30% of the oil and gas resources in the world is stored in a mudstones thin layer.The thin interaction of reservoir can be equivalent to the macro uniaxial anisotropic formation(or transverse uniform anisotropic formation,shorthand for TI formation).It has important significance and the real demand for oil and gas resources development to explore and recognize the strata.Because of the resolution is not enough,the traditional induction logging tool often makes this kind of thin oil reservoir mistaken for high water saturation layer and missed.Three-component induction logging tool is different with the traditional induction logging tool,and it can measure the full magnetic field strength tensor at one time,which can extract the detailed information of the transverse longitudinal formation.Thus in recent years the three-component induction logging method became an important direction of development of the unconventional reservoir logging technology.In the three-component induction logging,the forward modeling is the necessary foundation for the logging response characteristics and data processing,it can provide the basis for the effective analysis of formation physical properties,to help find the best drilling area.In order to investigate the response characteristics of the three component induction logging which under a variety of complex formation model,and study the influence of the three component induction logging response when change different parameters on it,this paper derives three dimensional frequency domain electromagnetic response difference computing format which based on Maxwell's electromagnetic response equations and applied the staggered-mesh finite difference method.And then makes a comprehensive in-depth study on the equations of coefficient of large sparse matrix,using the compressed row storage(CSR)to compress the discrete equation coefficient matrix storage,saving the computer storage space,reducing the amount of useless calculation and design the calculation program,and under the geological model of coil measuring response is obtained.Finally,we take a large number of numerical calculation for the horizontal formation and tilting complex formation of three-dimensional induction logging response,and analyzed the stratigraphic thickness,working frequency of the tools,electrical conductivity,mud invasion,formation fracture displacement,cross crack,and the dipping angle change on the influence of three-dimensional induction logging response.The paper found that the three-dimensional induction logging tool has strong detection capability in complex formations,and the longitudinal magnetic field component has a higher vertical resolution than horizontal magnetic field component,which has better sensitivity to the formation change.It can provide important theoretical basis and reference basis for parameters optimization design,and data processing of the three-component induction logging method.