Computer Codes

INDTRI is a code released earlier. This code is used to compute triaxial induction response in a 1D isotropic formation. This release is an improved version of the code released earlier. Bugs are fixed in the code. This code is now more robust and faster. Data accuracy is also greatly improved.

The FDM code can calculate the response of triaxial induction tools in 3-D arbitrary anisotropic media, as shown in Fig.1. This code overcomes the limitation of the numerical method based codes released by the Well Logging lab. Since the later can only be used in the simulation of the tools in the 1-D multi-layered transverse isotropic (TI). In addition, the effects of the borehole on the well logging response can also be investigated by this code.

The code AC_Laterolog_3.0 can compute the apparent resistivity and current density distribution of the AC dual laterolog (DLL) tool in two-dimensional (dip=0) environments. The physical tool geometry, focusing conditions, and the source information are defined in the input files. Consequently, this software can simulate any azimuthally symmetrical electrode-type tool for which the conditions on electrode voltages and currents are linear. The simulation model can consist of borehole, invasion zones, and multi-layer formation. Each layer can contain multi invasion profiles. The maximum number of invasion zones is defined by the constant MaxInvasionZone which is located in source file AC_Laterolog_3.0_10_Costant.f90. The default number of MaxInvasionZone is 10, and the number can be easily changed by the user to any value. Two dimensional finite element method (FEM) is used in the computation.

The code TRC_Kaufman_1.0 calculates through casing measurements when the source is a Kaufman’s tool, which is illustrated later. TRC_Kaufman_1.0 can compute the second derivative of potential and current density distribution of the Kaufman’s tool in two-dimensional (dip=0) environments. The simulation model can consist of borehole, casing, cement, invasion zones, and multi-layer formation. Each layer can contain multi invasion profiles. The maximum number of invasion zones is defined by the constant MaxInvasionZone which is located in source file TRC_Kaufman _10_Costant.f90. The default number of MaxInvasionZone is 10, and the number can be easily changed by the user to any value. Two dimensional finite element method (FEM) is used in the computation.

Telemetry_3.0 is based on a 2D FEM and is designed to calculate downhole telemetry system in the following environment:

1. System includes air, sea water, and earth formation.
2. System includes arbitrary borehole, casing, and drill pipe.
3. The source can be current source or voltage source.
4. One gap is inserted in the pipe, close to the side of drill bit. The source is added on the two side of the gap.
5. Outputs include magnetic field, current distribution, potential difference, gap impedance, etc.

The TRITI09_A.F and TRITI09_F.F Fortran codes can calculate the response of triaxial induction tools in 1-D multi-layered transverse isotropic (TI) formation, as shown in Fig. 1. They corrected version of the previously released DIPANI.FOR. TRITI09_A.F uses the fast Hankel transform to calculate the infinite integral of the highly oscillatory Bessel function while TRITI09_F.F uses Gauss-Laguerre quadrature to calculate the integral when dip angle is smaller than 82.5 degrees and uses fast Hankel transform when dip angle is larger than 82.5 degrees. TRITI09_F.F is faster for lower dip angles since less quadrature points are used. Users can choose to use either software according to their requirement.

This code calculates the electromagnetic fields and apparent conductivity of induction and MWD sondes in a cylindrically layered formation. Fortran codes for induction and MWD sondes already exist in the CIND94 and CMWD94 Software Packages. However, their absolute accuracy is only 0.00001, and the Bessel function routine used is not as accurate as routines currently available. The computations in the new code are all executed in double precision, and the Amos routine for the Bessel functions is employed. The new code is much more accurate than the original code, and can be used to verify other codes in a homogeneous case.

The TRIBIA08 Fortran code can calculate the response of a triaxial induction tool in a homogeneous biaxial anisotropic formation. The transducer axes of the sonde can be arbitrarily oriented with respect to the principal axes of the conductivity tensor of the biaxial anisotropic medium. Both responses, including nine components of the magnetic fields and the apparent resistivity can be computed.

3XTI08 is intended to replace the code INDANIH released a few years ago. 3XIT08 computes magnetic response of the tri-axial induction tools in deviated wells drilled in a transverse isotropic (TI) formation. Nine magnetic field components at the receiver location at each logging point are computed simultaneously. The software is a 1-D code and is applicable to logs in formation with dipping angle ranging from 0 to 89 degrees. The azimuth angle of tool can be any value between 0 and 360 degrees. Meanwhile, tool axis is allowed to have a rotation angle with respect to the formation anisotropy.

This code is used to calculate dielectric constant and conductivity of any given mixture with know microscopic structures. Current version is limited to 3D with isotropic materials. This code uses FDTD method and solving D and E for a given 3D rock structure.

This version of Well Log Inversion code added AIT tool simulation and data conversion function. This version is only limited to oil company uses. Any user using this code must obtain permission from Schlumberger.

The INVASION1D06 Fortran code can calculate water saturation, formation water pressure, salt concentration on water and formation resistivity as a function of the radial distance from the borehole center and the time (defined by the user) that has passed after mud filtrate started to invade the formation due to pressure differential between the borehole and the original formation pressure. The obtained formation resistivities at different time intervals can be used as the input to simulate MWD and induction tool responses at those intervals in order to study the effects of invasion on resistivity logs and improve the estimation and characterization of formation parameters like layer boundaries, invasion profile or permeability.

The code was 2-D FEM code designed to compute spontaneous potential (SP) logs when SSP was known in 2-D cases. The unknowns solved are current potential which can be used to plot current lines produced by dipole layers. Then the current potential is used to compute SP logs on the surface of tool. In the code, the tool radius is fixed at 1.3 inches. The borehole size is assumed to be 8 inches.

This code was developed based on FEM code developed by Dr. Weishan Han in 2004. The improvements are on computational speed using field symmetry. The use of field symmetry does not limit generosity of full 3D simulation. Therefore, the code is able to simulate tri-axial induction logging tool response in complex anisotropic formation with tilt angles, multi-layers, and multi-invasion zones. To simplify parameter input, this tri-axial code is divided into two different codes to handle different transmitter orientations in x direction and y and z directions.

This code is designed to compute the responses of Tri-Axial tool for transmitter in x direction. Another code is available in the same release to process source in y and z direction. The code uses the edge-based base, Frontal solver, and can handle frequency from several KHz to several MHz.

This code was developed based on FEM code developed by Dr. Weishan Han in 2004. The improvements are on computational speed using field symmetry. The use of field symmetry does not limit generosity of full 3D simulation. Therefore, the code is able to simulate MWD/LWD logging tool response in complex anisotropic formation with tilt angles, multi-layers, and multi-invasion zones. The code uses the edge-based base, Frontal solver, and can handle frequency from several KHz to several MHz.