A geometric analysis-based approach toward mechanical analytics of multi-packer completion tubular string

Abstract

Multi-packer completion strings have played a pivotal role in secure exploitation of oil and gas, increasing production and mitigating greenhouse gas emissions. While the integration of multi-packer structures has proven advantageous in oil and gas exploration, it has introduced complexities in load distribution, consequently giving rise to safety concerns. This study undertakes a thorough examination of the mechanical analysis pertaining to multi-packer completion strings. We present an analytical model for predicting the axial forces acting on the multi-packer string, utilizing the geometric constraint arising from the immobility of packers. It is demonstrated that the pressure differentials at the packers exhibit uniqueness in relation to both initial and boundary conditions, as well as the geometrical constraint. This paper provides an analytical solution for these pressure differentials. Novel concepts regarding the eigen-matrix of an N-packer completion string, influenced solely by Poisson’s ratio, a virtual (N+1)th packer and the eigen-depth and eigen-ratio of two adjacent packers, are proposed and their applications are discussed. Furthermore, this paper delves into a deeper examination of the multi-packer string’s underlying mechanism. A consistent algorithm grounded in geometric analysis is developed based on the analytical model. Validation of our model is performed using three practical cases across various operation conditions, and the results demonstrate the efficacy of this methodology in accurately predicting failure occurrences. Sensitivity analysis results further substantiate the robustness of this method in practical applications. Additionally, it has been shown that strategically positioning the packers in areas where the string is highly prone to fractures significantly enhances the safety of the multi-packer string system. The findings presented in this paper offer a foundational framework for analyzing the mechanical behavior of constrained strings. Furthermore, there is potential for the development of the analytical model to incorporate additional factors, such as string system with packers of semi-free or free movement. The proposed method is also of fundamental significance for safety evaluation of string systems in carbon storage projects, which is obtaining increasing attention in the context of carbon neutralization.