Modelling and improvement of the design of hinged centralizer for casing

Abstract

We have researched an important problem for the oil-and-gas field, which is the problem of centralizing of cases in wellbores with a complex profile. Usually this problem is solved by equipping the case in problematic areas with special centralizing devices. Centralizers have mutually competing requirements: low stiffness in order not to slow down the descent of the case into wellbore and high stiffness in order to provide proper clearance gap for high-quality cementing of the annular space. The aim of the paper is to solve this problem by means of the construction of a hinged-rod centralizer, additionally equipped with a thrust ring. To model the arch-shaped link of the centralizer, the classical theory of the flat rods is used. On the basis of analytical solution of contact problems with unilateral connections, we investigated the stress-strain state of the rod in two cases: before and after the interaction with the axial obstruction. We have determined the non-linear dependencies between the contact force and the mutual approach of the case and the wall of the wellbore, and also the expressions of the acceptable contact loadings that provide structural integrity of the construction.