Dynamic analysis and optimization of perforated tubing strings in deep-water wells under diverse operating conditions

Abstract

Deep-water well perforation is an essential process for enhancing the offshore oil and gas production. However, the shock loads generated by perforated operation pose significant safety risks to the integrity of the perforated tubing string system, with the potential for severe accidents. We conducted dynamic simulations of the perforation process and extracted the mechanical data of the perforated tubing string from different directions and locations at different time intervals with ANSYS/LS-DYNA. This paper uncovers the dynamic mechanical behaviors, identifies vulnerable areas of the perforated tubing string system, evaluates the tubing string's response patterns, and proposes optimization strategies for deep-water wellbore perforation by modifying parameters in the finite element model to simulate various perforating operation environments. The main finding are as follows: (1)the most significant displacement deformations, velocity variations, and localized equivalent stress concentrations occur at the bottom of the tubing string; (2) peak equivalent stress is observed at the top of the tubing string, and vulnerable areas is at both ends; (3) to effectively mitigate the explosive impact on the perforated tubing string during perforation, this paper proposes several measures, including maintaining proper alignment of the perforating gun, adjusting the unloaded portion of the gun, reducing perforation fluid density, lowering initial pressure in the wellbore, increasing the wellbore space, strategically arranging loading of charges, employing longer tubing, and moderately increasing the internal pressure of the tubing string; (4)through the validation of a field case in deepwater wellbore, this paper demonstrates that impact loads on downhole tools such as the perforated tubing string, packer, and manometer can be minimized with a comprehensive optimization strategy that include optimizing shock absorber quantity and position, establishing a safety distance for the packer, and modifying perforation parameters. This paper offers essential guidance and a theoretical framework for mitigating shock loads and improving the overall safety of the string system during deep-water wellbore perforation.