The Effect of Hydraulic Anchor Structure on Casing Deformation and Extrusion Stress

In this paper, an analysis is conducted on the structural characteristics of ordinary and carbide hydraulic anchor so as to optimizeits structure to reduce its damage on casings. A formula for the extrusion stress on the casing at the biting position of carbide hydraulic anchors is derived based on material mechanics theory, and the casing deformation and extrusion stress at the biting position of ordinary hydraulic anchors is analyzed by using finite element method. It was demonstrated that casings are damaged at different degrees by ordinary and carbide hydraulic anchors. Ordinary hydraulic anchors will cause less radial deformation and extrusion stress on the casing than carbide hydraulic anchors under the same tubing pressure differential.Based on the analysis results, screw tooth design should be adopted in hydraulic anchors.When the tubing pressure difference is the same,extrusion stress exerted on the casings at the biting position of carbide hydraulic anchors decreases by power-law index with wedge angles and tooth diameters, but increases polynomially with anchor diameters and axial loads (in smaller amplitude), and increases exponentially with anchor tooth back angles gently. Results indicate setting the wedge angle at 10°, the anchor tooth diameter 10-12 mm and the anchor diameter 40-50 mm.Research provides a theoretical basis for the structure design of hydraulic anchors.