Abstract: Sand filling control in horizontal wells is widely used in oil and gas development, but if mudstone exists, the possibility of sand filling failure will increase. In order to solve the failure of filling sand control when drilling a large section of mudstone in horizontal wells in offshore oilfields, through the research and analysis on existing technology, we compare and optimize the feasible treatment programs, and develop and apply a new filling tool. In the new tool design, the back plug, the positioning seal and the bottom bypass assembly form the bottom flow passage of the tool; the 177.8 mm blind tube, the 127 mm blind tube, and the corresponding bottom end are inserted into the sealed annulus to form the middle liquid flow passage; the upper bypass quick connection assembly is connected to the two layers of blind tubes and provides a liquid flow passage at the top. After the completion of the new tool, the reliability and functionality of the method are verified by means of weak point strength theory calculation and actual test. Finally, a field application is carried out in a well in QHD Oilfield. The results show that the new type of open hole fracturing completion tool is superior in performance and safe and stable.