Critical Erosion Simulation of Sand-carrying Gas Production at Y-shaped Wellhead of Gas Storage
The working system of "strong injection and strong production" in the production process of gas storage will easily lead to the erosion of pipe string, which will result in the failure of wellhead pipe string and bring hidden dangers to the safe operation of gas storage. The work aims to determine the erosion law of pipe string in the production process of gas storage, accurately predict the erosion rate of wellhead pipe string and identify the safety of pipe string. Based on the pipe string structure and production conditions of the injection-production well in Shuang-6 gas storage in Liaohe Oilfield and according to the theoretical model of gas-solid two-phase flow, the standard k-ε turbulence model was used to calculate the hydrodynamic characteristics of the continuous phase, describe the kinematic state and trajectory of discrete particles through the discrete model, and study the injection-production process of the gas storage and the wellhead erosion law under the conditions of different injection-production parameters.The numerical simulation results showed that the maximum erosion rate of different parts of the pipe string decreased nearly exponentially with the increase of production pressure. The maximum erosion rate of different parts of the string increased nearly exponentially with the increase of gas production rate. The maximum erosion rate of different parts of the string increased linearly with the increase of sand production rate. In addition, the erosion rate of the variable diameter part of the pipe string showed a downward trend with the increase of service time. When the chamfer of the variable diameter part of the pipe string was 5°, the erosion rate of the variable diameter part decreased, and finally it was basically the same as the erosion rate of the pipe wall.The erosion angle was set at 90°, the sand production particle size was 0.10-0.25 mm, and the sand production rate was 0.1-5.0 g/s. The experimental results showed that the sand blasting erosion test was carried out. The results showed that the numerical simulation results were quite different from the experimental results. At the same time, compared with Finnie model, McLaury model, Oka model and DNV model in classical theory, under the same working conditions, the erosion results solved by Fluent model were the closest to the erosion experimental results.Considering the erosion effect of integral Y-shaped gas production wellhead, based on the numerical simulation results, the erosion rate model of Y-shaped gas production wellhead string under sand production conditions is constructed by multiple regression analysis, and the sensitivity of sand production particle size to the erosion effect of string is poor. The maximum erosion rate of pipe string is proportional to the quadratic power of daily gas production, the negative quadratic power of pressure in wellhead and the first power of sand production rate. According to API RP 14E standard, the chart of critical erosion coefficient is established. At the same time, it is suggested that under the current sand production condition of gas storage, in order to make the gas storage meet the service life, the value of C is 180. Further considering the maximum production capacity of gas storage, it is recommended that the value of C is between 175 and 200.To sum up, this work establishes the erosion rate model of gas storage injection-production well string through numerical simulation research on the erosion process of gas storage string. According to the critical erosion theory, the design version of critical erosion coefficient of gas storage injection-production string is constructed, which provides key real-time and safe basic data guidance for engineers and technicians to accurately identify the production load and service safety conditions of gas storage injection-production string under real-time production conditions.
万方数据
维普
