Investigation on the Depth of Slip Hanger Teeth Bite into Casing and the Mechanical Properties of Casing under Different Suspension Loads in Ultra-Deep Wells

Abstract

There is great difficulty in controlling the setting load of the large-size slip casing hanger in the Northwest Oilfield in China, and a reasonable setting load is of great significance. This paper studied the relationship between slip hanger bite depth and suspension load in the Ф 273 mm WE-type slip hanger in the Northwest Oilfield in China through experiment, theoretical computation, and finite element analysis. The accuracy of the finite element model was proved by comparing the finite element simulation results with the experimental bite marks on the casing surface. The study results show that the bite mark of the slip insert in the casing is deeper in the lower part of the sitting position. When the hanging load increases from 1000 kN to 6000 kN, the maximum bite depth of the slips in the casing gradually increases with the suspension load. The residual collapse strength of the casing decreases correspondingly. When the residual collapse strength decreases to a certain value, the maximum suspension force corresponding to the bite depth of the slip insert can be obtained. Based on the finite element research results and theoretical equations, the stress distribution on the casing wall where the slips bite the deepest is obtained by derivation. The suggestions on improving the material structure of the casing under this stress were proposed. The limit of the setting load of the large-size casing wellhead for avoiding casing collapse was obtained, which is of great significance for guiding field-casing setting.