Simple control structure for stabilizing Core Annular Flow operation in heavy oil transportation

Abstract

This research aims to develop a simple regulatory controller to control a Core Annular Flow (CAF) in the oil and gas industry, focusing on transporting heavy oils. CAF is an economical method to transport viscous crude oil where less viscous liquid, typically water, is used to lubricate the pipe walls, creating an annular flow regime. However, managing the stability of CAF is challenging due to geometric variations, changes in pipeline flow direction, and emulsion formation. We used computational fluid dynamics (CFD) simulations to represent the CAF system and subsequently designed a simple control structure for the process. This process involved conducting both open-loop and closed-loop tests. The findings from the study indicate that the I controller significantly improves the system's response to disturbances in oil velocity by adeptly adjusting water velocity. This adjustment is crucial for maintaining the desired oil fraction and sustaining an annular flow pattern. An important observation was the effectiveness of the proportional gain in tracking the setpoint within annular flow regimes and the enhanced system stability achieved by increasing the integral action. The study concludes that the PI controller stabilizes operations in previously challenging conditions and expands the system's operational range.