Objective Notable erosion damages occur in skid-mounted choke manifolds during the choking process of high-pressure sour natural gas, thus necessitating effective detection methods.

Methods Taking the wellhead skid-mounted choke manifold L004-X1 in the Shuangyushi Lower Permian Gas Reservoir of Northwest Sichuan Gas Mine as the study object, a numerical model was developed using Fluent software to simulate the flow field and erosion process under high-pressure conditions (103 MPa) at the wellhead. The comprehensive analysis focused on the pressure field and velocity field within the choke skid under on-site operating conditions. Factors influencing the erosion of choke valve body, including mass flow rate, inlet velocity, diameter of solid impurity particles in natural gas, and pressure drop before and after the choke skid, were thoroughly investigated. Additionally, ultrasonic phased array technology was employed for onsite online and offline wall thickness detection of the temperature/pressure measuring casing at the outlet section of Well L004-X1. This study aimed to verify the feasibility of the proposed numerical simulation and on-site online detection method for choke skid erosion without requiring shutdown.

Results From a morphological standpoint, the inner wall surface of the valve spool exhibited a predominant distribution of dotted erosion. The temperature/pressure measuring casing at the outlet section showed continuous sheet erosion, with the most severe erosion observed on the lower face C, attributed to the force of gravity. The valve spool displayed the most significant erosion on its inner wall surface, followed by its outlet. The erosion rate increased with higher mass flow rates and inlet velocities of particles, while gradually decreasing and stabilizing with increasing particle diameters. A comparison of results between numerical simulation and on-site offline detection using ultrasonic phased array technology revealed an average relative error of 4.1% in the minimum wall thickness of the four faces of the temperature/pressure measuring casing at the outlet section. This finding verified the feasibility of the proposed numerical simulation. The on-site online and offline ultrasonic phased array detection methods demonstrated consistent results for the minimum wall thickness. Therefore, the online detection method is recommended to facilitate on-site operations.

Conclusion The findings of this study provide valuable theoretical guidance for the safe detection of field facilities in high-pressure sour gas reservoirs. However, the effect of H₂S corrosion was not considered in the numerical simulation study. It is suggested to conduct H₂S corrosion experiments under different gas pressures and velocities in further researches for more accurate prediction of erosion rate.