The structure of the DMS casing anchor is designed with two stages of fluke with different lengths. The first stage is shorter fluke adapted to the borehole with reduced diameter and hard formation, and the second stage is suitable for the borehole with loose and expanded diameter.  During the anchoring process, the two stages can interact with each other. The first stage opens first during construction. When the strength of the first stage is insufficient, the second stage opens automatically for joint anchoring, complementing each other.  The outer diameter of the anchor jaw is large, up to 560mm.  The tool is equipped with an anchor claw locking mechanism to prevent accidental opening during down hole process.  Built-in floating hoops, float shoes and guide shoes reduce completion string costs.  The two-stage flugs are distributed symmetrically at 90° along the axial direction. This design can not only improve the strength of the anchor, but also improve the adaptability and reliability of the anchor, so as to ensure the successful application of the anchor in shallow loose expanding formation, deep reducing diameter borehole and irregular hard borehole.  
      The two-stage casing anchor at the lower end of the casing string and directly connected with the casing. After the casing reaches the bottom of the well, the pump is circulated, and the drilling fluid is returned from the circulation hole. Normal cementing and impact pressure. After the rubber plug is pressed, sit on the upper rubber plug of the ground anchor, and then slowly hold back the pressure. When the pressure reaches 15-20 MPa, cut the shear pin, the ground anchor rubber plug seat moves down, push the center tube and the connecting rod group, and open The two-stage anchor claw makes it anchored to the well wall, and the prestress of the wellhead lifting reaches the designed tonnage or length under the pressure holding state, and the casing is set afterwards, and the prestress construction of the lifting casing is completed.