Optimization of sealing solutions for insertion sealing devices in deep formation drill rod testing

This study addresses the limitations of conventional formation testing technologies in meeting the engineering demands of deep and heavy oil reservoir testing. A novel multifunctional gas-lift testing method is proposed, wherein gas is injected through the narrow annulus between the drill rod and tubing to facilitate gas-lift production. To ensure effective annular sealing during the gas-lift process, a specialized insertion sealing device was developed. Structural analysis identified the sealing mechanism as a critical component influencing overall device performance. Based on operational conditions, three sealing configurations were designed and comparatively evaluated to determine the optimal solution. A V-ring seal was selected for further investigation, and a two-dimensional axisymmetric finite element model was established to simulate its sealing behavior under three operating conditions. Subsequently, a high-pressure sealing test at 50 MPa was conducted to validate the device’s performance. Experimental results demonstrate that the integrated V-ring sealing assembly, composed of fluororubber and PTFE materials, provides robust sealing capability. The structure remained intact under preloading and exhibited reliable performance under both internal and external loading conditions, withstanding continuous operation at 20 MPa without leakage. Throughout the entire pressurization and sustained pressure-holding phases, no visible leakage occurred, and the seal showed no signs of crushing, extrusion, or permanent deformation. These results confirm the device’s suitability for high-pressure and deep-sea applications. The proposed tool offers a simple yet effective sealing solution, providing technical support for the application of insertion sealing technology in deep and heavy oil reservoir development. This paper addresses the issue that existing conventional formation testing processes and technologies cannot meet the engineering requirements for testing deep and heavy oil reservoirs. A novel multifunctional gas-lift testing process is put forth, which entails the injection of gas through the narrow annulus between the drill rod and the oil pipe for gas-lift operations. Furthermore, an insertion sealing device has been designed to achieve annular sealing during gas-lift oil extraction. An analysis of the device revealed that the sealing mechanism is of critical importance to its overall performance. Accordingly, three sealing structures were proposed based on the working conditions, and their performances were analysed to select the optimal solution. Furthermore, a stress analysis was performed on the selected V-ring seal. A two-dimensional axisymmetric model of the V-shaped combination sealing mechanism was constructed to discuss its sealing performance under three different conditions. The findings demonstrate that the integrated assembly methodology utilising V-ring seals comprising two distinct materials- fluoro rubber and PTFE- attains a substantial sealing efficacy. The V-ring composite sealing mechanism is capable of withstanding preload conditions without failure. It can withstand a medium pressure of 20 MPa and continue to operate without leakage under both inward and outward stroke conditions, ensuring that the sealing performance meets the requirements for deep-sea operations. The tool has a simple structure and reliable performance, providing a basis and reference for using insertion sealing devices in deep-sea heavy oil applications.