Abstract: The study of the LWD (Logging While Drilling) azimuthal gamma imaging mode under different geological structures can provide bases for fast and accurate identification of drilled formation. The detection model of LWD azimuthal gamma is set up, and physical models of several positions of the formation and gamma detector is established, combining the descartes coordinate with the spherical coordinate, an azimuthal gamma log response algorithm under different position models is derived. Comparing the simulated results with the measured results of the azimuthal gamma ray logging tool, it is proved that the algorithm can effectively simulate the response characteristics of the azimuthal gamma, and has a high accuracy. It simulates the gamma image and analyzes the characteristics of the image, which provides a theoretical basis for real-time geosteering.

Key words: LWD azimuthal gamma, gamma ray flux, strata model, forward simulation