Mechanical behavior of solid expandable tubular in curved borehole based on transverse beam bending theory

Abstract

With the development of shale gas, casing losses in horizontal and curved borehole sections become more and more serious. It is a new attempt to repair horizontal casing with solid expandable tubular (SET), but the passability and expansibility of SET in curved hole will determine the success of this technique. In this paper, based on the bending theory of beam and finite element technique, the theoretical expression of the limit length of SET through curved borehole is derived, and a three-dimensional dynamics model considering friction and contact nonlinear wellbore- SET-expansion cone coupling is established by CAE. Finally, the dynamic load coefficient is introduced to modify the theoretical calculation results, and the extensibility of the SET is studied. The results show that: (1) The theoretical calculation formula of SET flexible passage has high reliability. Finite element technology is used to introduce dynamic load coefficient to modify it, and the dynamic load coefficient is 0.9. (2) SET flexible pass is more in line with practical construction than rigid pass, and the limit length of flexible pass is far greater than that of rigid pass. (3) It is recommended that the expansion rate should not exceed 12% when the SET length meets the limit for SET in curved holes. This value is about 50% lower than the ultimate expansion rate in vertical wells. The results of this paper provide theoretical support for the SET's passability and expansibility in curved borehole sections.