Formation law and prediction of two-phase flow accumulation in medium and low water-content gathering and transportation pipelines

Purpose As China's inland oil fields gradually enter the middle and later stages of development, the proportion of water content in the low and medium water-content surface gathering and transportation system increases year by year. Under some working conditions, liquid accumulation may form at the bottom of the gathering and transportation pipeline, creating a corrosive environment for the pipeline and increasing the risk of corrosion failure in the surface gathering and transportation system. Method A numerical simulation study was conducted on the formation of liquid accumulation in the oil-water two-phase flow characteristics of the low and medium water-content gathering and transportation pipelines. The formation law of bottom liquid accumulation was simulated under different pipe diameters, flow rates, water content, and inclination angles, obtained the volume fraction and position of liquid accumulation under different working conditions, explored the influencing factors and formation laws of liquid accumulation, drew the flow pattern and liquid accumulation state table of oil-water two-phase flow, and established a prediction model for liquid accumulation in gathering and transportation pipelines using the random forest method based on this. Result The formation process of bottom fluid accumulation can be roughly divided into four stages, namely coagulation, coalescence, precipitation, and sedimentation in the low and medium water-content gathering and transportation pipeline. In the simulated working conditions, the accumulation of liquid is positively correlated with the flow rate, negatively correlated with the water content, and shows a trend of increasing first and then decreasing with the inclination angle and pipe diameter. The probability of bottom accumulation and stratified flow formation is 50%, which is highly prone to pipeline corrosion environment; Establish a fluid accumulation prediction model using the random forest method, with a prediction error of approximately 10% or less. Conclusion The research results can provide reference and exploration path for the formation law of two-phase flow and liquid accumulation in the low and medium water-content gathering pipelines. In the future, scientific treatment of bottom liquid accumulation phenomenon can be carried out by changing the operating parameters of gathering pipelines, such as selecting more suitable pipeline inclination angle and diameter in the design stage and selecting more suitable flow velocity in the production stage. The formation pattern and prediction model of fluid accumulation can provide theoretical reference for the treatment of pipeline corrosion in oilfield surface gathering and transportation.