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The performance of a transient multiphase flow simulator was evaluated using high-quality field data measured in a large diameter gas-condensate offshore production system during different operating conditions (pigging, production shut-in and restart, production ramp-up, quasi steady state). Production data included measurements recorded from more than 120 sensors (pressure, temperature, flow rate, monoethylene glycol (MEG) fraction, slug catcher volume) during a three-year production time span. After thorough data screening and analysis, 19 distinct subsets encompassing both steady state conditions and at least one pigging event per subset were selected as benchmarks for validating simulation results. For each subset, a simulation model was developed to account for ambient and operating conditions, fluid properties, bathymetry profiles, thermal insulation and pipe burial, and hydrate inhibitor tracking (MEG). A comprehensive statistical analysis comparing predicted and measured pressure drop, pigged liquid volumes, outlet temperatures, and rich MEG mass fractions over the three-year time period demonstrated that the simulator predictions were in good agreement with the field data. The analysis included an uncertainty assessment of the measured production flow rates and volumes to better estimate the simulator accuracy. It was found that the simulator predicted both the cumulated rich MEG and condensate volumes received at the delivery point within the measurement uncertainty. The predicted rich MEG fractions at delivery were also in good agreement with the measurements, underlining the reliability of the inhibitor tracking module of the simulator. The pig travel time and the total liquid volume displaced by the pig during each pigging event were the main parameters considered to evaluate the accuracy of the simulator; both were predicted within a 10% error margin. Multiphase flow simulators are often developed and tuned against experimental data recorded in small to medium diameter scale pilots. The opportunity to validate a transient multiphase flow simulator against measured operating conditions in large diameter pipelines over an unprecedented three-year time span is valuable, not only for quantifying the performance of the simulator, but also for assessing its scalability.

The entrainment of liquid droplets, occurring in a limited range of gas and liquid flow conditions within the stratified flow region, could represent an effective way to transport a non-volatile liquid corrosion inhibitor through the gas phase and combat top of the line corrosion (TLC). However, such an approach is only viable if the inhibitor can reach the top of the pipe and deposit at a rate higher than the local rate of condensing water can dilute it. This work presents a combined modeling and experimental methodology to determine the onset of droplet entrainment from the bottom and deposition at the top of the line. A modeling approach predicting the droplet entrainment onset is proposed and validated against new multiphase flow data recorded in a large scale flow loop, at operating conditions similar to those encountered in gas-condensate production facilities. Additionally, TLC experiments were performed in the same flow loop under simulated water condensation conditions to measure the actual corrosion at different rates of inhibiting droplet deposition. The results confirm that the droplet entrainment/deposition can effectively mitigate TLC when operating parameters are accurately controlled.