Modeling and Durability Behavior of Erosion–Corrosion of Sand Control Screens in Deepwater Gas Wells

Abstract

Deepwater gas wells usually have high production rates, which result in high-speed sand movement along with the gas flow and acid components such as CO2 in the gas flow. The erosion and corrosion effect intensifies the damage to sand screens and can further lead to sand control failures, which endanger the safety of production operations. In this paper, using a differential rotation device to simulate erosion, corrosion, and erosion–corrosion, experiments observing the impacts of several factors on sand screens were carried out. The factors include CO2 partial pressure, temperature, flow velocity, sand content, and sand particle size. Their impacts on erosion, corrosion, and erosion–corrosion rate are inspected independently, and the sensitivity of factors to the erosion–corrosion rate of a sand screen was determined using the range method. Traditional erosion models involving flow rate, sand content, and sand grain size and traditional corrosion models involving CO2 partial pressure and temperature are taken as references, and an erosion–corrosion coupled model of sand screens is established based on the experimental results using the multivariate regression analysis. With critical damage thickness taken as the failure criterion of a sand screen, a prediction method for sand screen failure is formed and is applied to the case study of the S deepwater gas field. The results show that under the experimental conditions, the screen loss rate due to erosion–corrosion is significantly higher than that of erosion only or corrosion only and is even higher than the sum of both. The erosion–corrosion rate increases with the increase of CO2 partial pressure, temperature, flow velocity, sand content, and sand particle size. It has an exponential relationship with the negative reciprocal of temperature, a linear relationship with the partial pressure of CO2, and power fitting relationships with flow velocity, sand content, and sand particle size. The ranking of sensitivities to the erosion–corrosion rate of high-quality screens is as follows: sand content > flow velocity > temperature > sand particle size > CO2 partial pressure. The error between the predicted results by the proposed model and the experimental results is in the range of 0.44–9.47%. The erosion–corrosion rate of sand screens in each production well of the S gas field is in the range of 0.0111–0.0521 mm/a, while the durability of the screens is 14–68 years. The erosion–corrosion rate model of a sand screen and the prediction method for sand screen failure proposed in this paper provide theoretical support to the durability evaluation of sand screen in deepwater gas wells, which is of great significance for ensuring the safe and efficient development of offshore oil and gas resources.