Development and Test of Internal-Cutting Down-Attached Anchor

To solve the problems of low cutting efficiency and unstable cutting fracture quality caused by severe vibration and eccentric rotation of the cutter device in downhole hydraulic cutting operation of tubing and casing， a cutter down-attached anchor tool was developed， which could also realize conventional power up-attachment under special working conditions. The tool uses a rotary seal structure to achieve the “rotation + anchoring” function of the anchor， and solves the problems of small anchoring range and unstable anchoring through blade-type anchor blocks and a dual-piston structure. The field test results show that the down-attached anchor and the hydraulic cutter exhibit excellent operational compatibility. Compared with up-attached anchor cutting operation， the tool string is not eccentric after cutting operation of down-attached anchor， and the overall cutting time is reduced from 4 min to 2 min（ø73.0 mm tubing）， with cutting time shortened by 50%. The down-attached anchor structure can simultaneously anchor at least two sizes of tubing， indicating that it maintains anchoring stability even at larger opening angles. The tool features a simplified and reliable structure， with universal applicability across multiple sizes and working conditions. The successful development of the tool provides guidance for further improving the efficiency of field cutting operations.