MULTIPHASE FLOW IN VERTICAL AND DEVIATED PIPES

Lead Research Organisation: Cranfield University
Department Name: Sch of Engineering

Abstract

This proposal addresses the vital issue of prediction of multiphase flows in large diameter risers in off-shore hydrocarbon recovery. The riser is essentially a vertical or near-vertical pipe connecting the sea-bed collection pipe network (the flowlines) to a sea-surface installation, typically a floating receiving and processing vessel. In the early years of oil and gas exploration and production, the oil and gas companies selected the largest and most accessible off-shore fields to develop first. In these systems, the risers were relatively short and had modest diameters. However, as these fields are being depleted, the oil and gas companies are being forced to look further afield for replacement reserves capable of being developed economically. This, then, has led to increased interest in deeper waters, and harsher and more remote environments, most notably in the Gulf of Mexico, the Brazilian Campos basin, West of Shetlands and the Angolan Aptian basin. Many of the major deepwater developments are located in water depths exceeding 1km (e.g. Elf's Girassol at 1300m or Petrobras' Roncador at 1500-2000m). To transport the produced fluids in such systems with the available pressure driving forces has led naturally to the specification of risers of much greater diameter (typically 300 mm) than those used previously (typically 75 mm). Investments in such systems have been, and will continue to be, huge (around $35 billion up to 2005) with the riser systems accounting for around 20% of the costs. Prediction of the performance of the multiphase flow riser systems is of vital importance but, very unfortunately, available methods for such prediction are of doubtful validity. The main reason for this is that the available data and methods have been based on measurements on smaller diameter tubes (typically 25-75 mm) and on the interpretation of these measurements in terms of the flow patterns occurring in such tubes. These flow patterns are typically bubble, slug, churn and annular flows. The limited amount of data available shows that the flow patterns in larger tubes may be quite different and that, within a given flow pattern, the detailed phenomena may also be different. For instance, there are reasons to believe that slug flow of the normal type (with liquid slugs separated by Taylor bubbles of classical shape) may not exist in large pipes. Methods to predict such flows with confidence will be improved significantly by means of an integrated programme of work at three universities (Nottingham, Cranfield and Imperial College) which will involve both larger scale investigations as well as investigations into specific phenomena at a more intimate scale together with modelling studies. Large facilities at Nottingham and Cranfield will be used for experiments in which the phase distribution about the pipe cross section will be measured using novel instrumentation which can handle a range of fluids. The Cranfield tests will be at a very large diameter (250 mm) but will be confined to vertical, air/water studies with special emphasis on large bubbles behaviour. In contrast those at Nottingham will employ a slightly smaller pipe diameter (125 mm) but will use newly built facilities in which a variety of fluids can be employed to vary physical properties systematically and can utilise vertical and slightly inclined test pipes. The work to be carried out at Imperial College will be experimental and numerical. The former will focus on examining the spatio-temporal evolution of waves in churn and annular flows in annulus geometries; the latter will use interface-tracking methods to perform simulations of bubbles in two-phase flow and will also focus on the development of a computer code capable of predicting reliably the flow behaviour in large diameter pipes. This code will use as input the information distilled from the other work-packages regarding the various flow regimes along the pipe.

Publications

10 25 50
 
Description Through the use of tomography,the flow behaviour of the 250 mm diameter riser was characterised. It was confirmed that conventional slug flow does not exist with continuous gas injection. Instead churned flow was the dominant regime. Large Taylor like bubbles can exist provided their separation distance is larger than 20 diameter. Rise velocity of these bubbles is the same as that in small diameter pipes
Exploitation Route Results are used by multiphase flow code developers to enhance the performance of their code. This is fundamental work. However the results had led to further investigations supported by oil companies. Exploratory discussion has been held with volcanologist linking vertical pipe flows to mechanism of eruption.
Sectors Energy

 
Description Industrial reearch from BP
Amount £800,000 (GBP)
Organisation BP (British Petroleum) 
Sector Private
Country United Kingdom
Start 01/2011 
End 12/2013
 
Description Multiphase Flow Metrology for Oil and Gas Production
Amount € 121,464 (EUR)
Funding ID ENG58 
Organisation European Association of National Metrology Institutes (EURAMET) 
Sector Charity/Non Profit
Country European Union (EU)
Start 06/2014 
End 05/2017
 
Description Research support from Chevron
Amount £240,000 (GBP)
Organisation Chevron Corporation 
Department Chevron Energy Technology
Sector Private
Country United States
Start 01/2011 
End 12/2013
 
Title Multiphase flow test facility 
Description Two large scale experimental facilities have been developed to study multiphase flows (oil,water, gas). 
Type Of Material Improvements to research infrastructure 
Year Produced 2013 
Provided To Others? Yes  
Impact The facilities enable near industrial scale experimentation to be carried out. Output have been encapsulted in engineering design and modelling tools of sponsor companies for better assurance of oil and gas production 
 
Title Multiphase flows behaviour data base 
Description Data collected from a range of experiments are collated into a data base. Data include pressure, hold up and other time series. 
Type Of Material Database/Collection of data 
Provided To Others? No  
Impact The data are use to validate numerical models, both in house and commercial codes 
 
Title Method, controller and system for controlling the slug flow of a multiphase fluid 
Description A new methodology to mitigate slugging using top side information, particularly suitable for brown fields 
IP Reference GB0905375.2 
Protection Patent granted
Year Protection Granted 2009
Licensed Commercial In Confidence
Impact Further research funding from energy companies to continue research and development