The New Tool Design of Ultra-deep Azimuthal Electromagnetic Resistivity Logging-while-drilling Based on Gray Relational Analysis Method

During the hydrocarbon exploration and development, resistivity Logging-While-Drilling (LWD) plays an important role in formation evaluation and geosteering. Due to the insufficient investigation depth and azimuthal detection of the conventional resistivity LWD, its application to the multi-boundary, far-boundary identification and formation evaluation is limited in the complex reservoirs. Therefore, the study on new tool design of ultra-deep azimuthal electromagnetic resistivity LWD is proposed in this paper. Firstly, we made a forward numerical simulation of azimuthal electromagnetic resistivity LWD based on the Fast Hankel Transform method. Then, the logging response law was analyzed for the reasonable range of the tool parameters design. Owing to modern technology limitations, to achieve the ultra-deep azimuthal detection goal with detectable signal, the selection of relevant tool parameters has become a major problem. So, we proposed the gray relational analysis method to quantify the influence of tool parameters on signal strength and depth of investigation. Finally, the structure of the ultra-deep azimuthal electromagnetic resistivity LWD tool is obtained and the depth of investigation is more than 25 meters theoretically. This design can lay reliable theory basis for efficient geosteering and formation evaluation in the highly deviated and horizontal wells in the future.