Transient modeling and simulation of piston devices moving through single-phase and two-phase flows in pipes applied to pigs and plungers

Abstract

The passage of piston devices through pipes is commonly used in the oil and gas industries for the purposes of cleaning, monitoring, and increasing production efficiency. These devices are not self-driven and require their interaction with the flow entailing a pressure discontinuity across the piston body that drives it along the pipe. To ensure the proper operation of such devices it is crucial to predict the dynamics of the piston and its effects on the flowline. In this work, two modeling approaches are studied for pigs, and one model is proposed for a plunger upstroke. The pig model is applied to single-phase flow, and two-phase flow, including the bypass flow through the piston body. The plunger upstroke model includes the effects of liquid fallback and the gas slippage through the plunger body. In addition, a new methodology is proposed for the coupling of the piston models with the transient one-dimensional flow models. For the two-phase flow models, two two-fluid models are tested with different numerical methods, with the combinations of model-method being validated through benchmarking. The results obtained with the pig model are compared with results from the literature under single-phase and two-phase stratified flow. The results obtained with the plunger upstroke model are also validated with data from the literature, and with experimental data acquired during this work