Abstract: Using the geosteering technology in Sudan oilfields can break the western technology monopoly and solve the technology challenge during the horizontal well drilling process. This article uses Assel-15H as an example, carrying out pre-drilling geological risk analysis. Combined the 3-D geological modeling and the oriented geosteering technology, making full use of the LWD data and rebuilding the 3D geological model during the drilling process, a high drilling footage has been finally achieved. The success of this horizontal well gives a reference on how to use the geosteering technique in the complex fault block reservoir and how to make the proposed solutions in the horizontal well drilling.