A new theory for modeling transport and deposition of solid particles in oil and gas wells and pipelines

Abstract

The deposition of asphaltene, wax, hydrates, scale, and even transfer of sands in oil wells and pipelines are serious problems that cause production interruptions and lead to substantial economic losses. The present study opens a new window for solving this unresolved problem. Accordingly, an improved Eulerian deposition model that incorporates various mechanisms of particle transport and deposition (e.g., molecular and turbulent diffusion, turbophoresis, thermophoresis, and surface roughness) was extended to predict solid deposition in oil wells. In this paper, to make it possible to predict deposition in inclined and horizontal pipes, the model was modified to include the gravitational settling effect. Moreover, using this model, a new method was proposed to determine the particle size distribution and particle flocculation function. It was first validated by predicting particle deposition in turbulent airflow and showed very good agreement with a wide range of published observation data. Then the model was used for predicting the thickness profile of asphaltene deposition in two laminar flow capillary tube experiments reported in the literature. This model, for the first time, has predicted asphaltene deposition profiles with high accuracy, especially without the use of empirical parameters. The predictions of this model are as accurate as particle tracking methods but at much lower computational costs. This study demonstrates that under certain conditions in laminar flow, deposition is dominated by gravitational settling, while it has been hypothesized previously that asphaltene deposition predominantly occurs by diffusion. The results reveal that particle size distribution plays a vital role in asphaltene deposition modeling. The findings of this study can help for a better understanding of the effective mechanisms of asphaltene deposition. This is the most versatile theory that can be adapted with various flow conditions. Since this approach does not depend on the solid type, it can be similarly applied to predict the behavior of other solid-fluid flow assurances in oil and gas facilities. Modeling the solid solution and multi-solid phase behavior are other capabilities of the developed methodology. The high accuracy of this approach and using minimum adjustable parameters offer many avenues for future development to evaluate particle deposition in real field applications.