An inertial two-phase model of wax transport in a pipeline during pigging operations

Abstract

Pig in pipelines performs operations for cleaning the pipe interior and internal inspection. In the past few years many 1D models have been developed to simulate the process because of their reduced computational cost; however, they rely on simplifications which are not always valid. In this paper, the results of a three-dimensional (3D) numerical investigation of the interaction between a waxy-oil and a dynamic sealing pig in a pipeline are presented. The results are obtained at a reduced computational cost by using a moving frame of reference, and an "injection" boundary condition for the wax deposited on the wall. The effect of the temperature and the wax particles' size has been investigated. The 3D results show the structure assumed by the debris field in front of the pig. In particular, a lubrication region at the bottom of the pipe, whose dimensions are temperature dependent, is shown. This information cannot be deduced from 1D modeling. The influence of the oil on the mixture viscosity and the internal bed dynamics are discussed. This work provides insights into the interaction between the debris field in front of the pig and pipeline hydraulics.

A non-inertial two-phase model of wax transport in a pipeline during pigging operations

“…In analogy with Boghi et al (2017a), the dynamics will be described in a frame of reference fixed to the pig center of mass. This approach has been already used in 1D modeling (Minami & Shoham, 1995;Nieckele et al, 2001; Hosseinalipour et al, 2007b;Tolmasquim & Nieckele, 2008).…”

“…Despite very useful in pipeline engineering, 1D models do not capture important details of the pig-flow motion. A series of three-dimensional (3D) Computational Fluid Dynamics (CFD) simulations describing the interaction of the waxy oil with a moving sealing pig was presented by Boghi et al (2017a). The influence of temperature and particle size was discussed.…”

“…Despite more than two decades of research, the full 3D flow of the wax-inoil slurry coupled with the bypass pig dynamics, has not been investigated computationally yet. Three-dimensional numerical simulations have been successfully used to study the flow of the wax-in-oil slurry coupled with the sealing pig (Boghi et al, 2017a). However, that approach is not applicable to the bypass pig case, since: i) the pig velocity and the mean crude-oil velocity are decoupled; ii) the pig and pipe frames of reference are non-inertial.…”

“…In this paper a series of 3D CFD simulations describing the interaction of a waxy oil with a moving bypass pig are presented. For this purpose, the model developed in Boghi et al (2017a) has been modified as follows: i) the pig velocity is calculated by solving the pig momentum equation; ii) the waxin-oil slurry motion is described in the pig non-inertial frame of reference; iii) the drift-flux model has been modified to include the pig acceleration; iv) the effect of turbulence, due to the oil jet, has been taken into account.…”

“…The sealing pig study of Boghi et al (2017a) is referenced to remark the differences with the bypass pig case.…”