A stable numerical method to simulate array induction and measurement-while-drilling (mwd) logs is presented. The algorithm is based on a horizontal eigenmode expansion method. Mode propagation in the vertical directi...
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A stable numerical method to simulate array induction and measurement-while-drilling (mwd) logs is presented. The algorithm is based on a horizontal eigenmode expansion method. Mode propagation in the vertical direction is described by three-layer modules. Within each module, general transmission and reflection coefficients are obtained by tracing the propagation of the modes. The multilayer cases are treated as a cascade of such modules. Owing to the mode-tracing algorithm, numerical stability and efficiency are superior to the other methods. This numerical algorithm is applied to the simulation of array induction and mwd logs in formations with both vertical and horizontal layers.
A measurement-while-drilling (mwd) neutron porosity tool has been designed that is superior to wireline porosity tools in several respects. Longer sample periods and greater porosity sensitivity reduce the statistical...
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A measurement-while-drilling (mwd) neutron porosity tool has been designed that is superior to wireline porosity tools in several respects. Longer sample periods and greater porosity sensitivity reduce the statistical uncertainty in the mwd porosity measurement. Most of the borehole effects that perturb the measurement (salinity, mud weight, and borehole size) are reduced or nonexistent because the drill stem virtually fills the hole during drilling. Formation effects, lithology, and salinity changes, are comparable to or less than those for the wireline measurement. A sophisticated computer model was used to develop the initial design for this instrument and to estimate its response characteristics. Simulated response data are compared with experimental data to demonstrate the validity of the model. The response characteristics are superior to those of the wireline device.
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