Simulation Analysis of Soft Focusing of Azimuth Laterolog Resistivity Imaging LWD Tool
When logging while drilling directional lateral instruments work in formations,due to the long length of the drill collar,the surface potential attenuation is severe.The current flowing out of the drill collar will produce axial components,which cannot flow out strictly perpendicular to the surface of the drill collar,resulting in inaccurate measurement results.To address this issue,five soft focusing working modes are designed based on the electrode structure of the azimuth laterolog resistivity imaging logging tool(RIT),and expressions for calculating the azimuth lateral electrode current and apparent resistivity under different working modes are provided.The soft focusing working mode can simulate the simultaneous operation of symmetric antennas with different source distances to maintain the surface equipotential of the drill collar,and obtain more accurate axial current through linear superposition difference approximation.By using the three-dimensional finite element method to calculate the response of different soft focusing working modes in gradually changing thin interlayers,and comparing it with the original logging response.The results show that the soft focusing method can smooth out the peak and step phenomena at the interface of a single transmitting antenna,and is more accurate in identifying thin layers and calculating apparent resistivity.It has certain guiding significance for the interpretation of actual logging data of instruments.
logging while drilling resistivity loggingazimuthal laterolog resistivitypotential decaysoft focusdetection characteristic
万方数据
维普
