A distortion model test method of the casing string system considering FSI

Abstract

To solve the problem of prototype test’s high cost and difficulty of the casing string system in shale gas horizontal wells, this paper proposes a large-scale distortion model test method for the casing string system. Firstly, the elastic centralizer is simplified as elastic support, and the dynamic model of casing string system is established by finite element method. Then, the test platform of casing string system is designed and built. The modal test results show that the maximum error of the first five natural frequencies between the numerical calculation and the test results is 5.12 %, which verifies the correctness of the dynamic model of casing string system. On this basis, the distortion model’s constant power similarity law (CPSL) and power function similarity law (PFSL) are obtained by the dimensional analysis method and the least square method. The CPSL and PFSL are used to predict the vibration characteristics of the prototype casing string system by distortion models with different scaling ratios. The calculation and analysis show that the prediction accuracy of the PFSL is higher than CPSL’s with the same scaling ratio, and the PFSL can accurately predict natural frequency of the prototype casing string system within a large-scale distortion range and greatly reduce the test cost.