Optimum design of downhole chokes with high sulfur content and large pressure difference

Abstract

Natural gas resources are abundant in southwest China, but the exploitation environment with high pressure and sulfur always affects the working performance of downhole chokes, which in turn restricts the output of natural gas. In this paper, a high sulfur resistance fixed downhole choke is designed for high temperature (120°C), high production rate and high pressure difference (105MPa) sand-producing Wells. Through the nozzle discharge model to simulate the flow of the fluid through the nozzle, with Bono Maleev method to predict the hydrate formation conditions of downhole choke for the design of the structure. According to the failure forms of different parts, the materials were optimized, and the high sulfur resistant 3YC51 alloy, hard alloy and wear and corrosion resistant sulfur resistant rubber were selected through the test to improve the service life of the choke in the high sulfur high-pressure gas well and ensure the reliability of the tool. The results of numerical analysis on the tool holder and the pressure test of the Laboratory seal show that the choke designed has a good sealing and pressurization performance in the high temperature and high pressure difference environment of 120°C and 105MPa, and it can realize the function of lowering the pressure at the bottom of the well under this working condition, meeting the feasibility requirements. Through this design, the design and improvement of high sulfur gas well tool and new choke has guiding significance.