MULTIPHASE FLOW IN VERTICAL AND DEVIATED PIPES

该建议解决了海上油气开采中大直径套管内多相流预测的关键问题。立管基本上是一个垂直或接近垂直的管道，将海底收集管网（出油管）连接到海面设施，通常是一个浮动接收和处理船。在石油和天然气勘探和生产的最初几年，石油和天然气公司选择最大和最容易进入的海上油田首先开发。在这些系统中，导管相对较短，直径适中。然而，随着这些油田的枯竭，石油和天然气公司被迫在更远的地方寻找能够经济开发的替代储量。因此，人们对更深的沃茨以及更严酷和更偏远的环境越来越感兴趣，特别是在墨西哥湾、巴西坎波斯盆地、设得兰群岛西部和安哥拉阿普蒂亚盆地。许多大型深水开发项目位于水深超过1 km的区域（例如，Elf的Girassol位于1300 m处，Petrobras的Roncador位于1500- 2000 m处）。为了在这种系统中利用可用的压力驱动力输送采出流体，自然导致了比先前使用的那些（通常75 mm）直径大得多的套管规格（通常300 mm）。对这种系统的投资已经并将继续是巨大的（到2005年约为350亿美元），其中立管系统约占成本的20%。预测多相流立管系统的性能是至关重要的，但非常不幸的是，用于这种预测的可用方法的有效性是值得怀疑的。其主要原因是，现有的数据和方法是基于对较小直径管（通常为25-75 mm）的测量，以及根据这些管中出现的流型对这些测量的解释。这些流型典型地为气泡流、段塞流、搅动流和环状流。现有的有限数据表明，较大管道中的流型可能完全不同，在给定的流型内，详细的现象也可能不同。例如，有理由相信，正常类型的弹状流（由经典形状的泰勒气泡分隔的液弹）可能不存在于大管道中。通过三所大学（诺丁汉、克兰菲尔德和帝国理工学院）的综合工作方案，将大大改进有信心地预测这种流动的方法，这将涉及更大规模的调查以及在更密切的规模上对特定现象的调查以及建模研究。在诺丁汉和克兰菲尔德的大型设施将用于实验中，在管道横截面的相位分布将使用新的仪器，可以处理一系列的流体进行测量。克兰菲尔德试验将采用非常大的直径（250 mm），但将限于垂直、空气/水研究，特别强调大气泡行为。相比之下，诺丁汉的试验将采用稍小的管道直径（125 mm），但将使用新建的设施，在这些设施中，可以采用各种流体来系统地改变物理性质，并可以使用垂直和略微倾斜的测试管道。在帝国理工学院进行的工作将是实验性的和数字化的。前者将侧重于研究波的时空演变在搅拌和环形几何形状的环形流;后者将使用界面跟踪方法来执行模拟气泡在两相流中，也将侧重于开发一个计算机代码能够可靠地预测大直径管道的流动行为。该代码将使用从其他工作包中提取的关于管道沿着各种流动状态的信息作为输入。

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.