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1、中国石油大学（华东）本科毕业设计（论文）外文翻译中国石油大学（华东）本科毕业设计（论文）外文翻译学生姓名：王亮学 号：04051618专业班级：自动化04-6班指导教师：华陈权 2008年6月20日18英文资料Multi-phase Flow Analysis in Oil and Gas Engineering Systems and its ModellingTwo-phase flow is very common in industrial processes and its applications were already in use in ages as remote as t
2、he era of Archimedes. At the present time, many industrial processes rely on multi-phase phenomena for the transport of energy and mass or for material processing. During the last century, the nuclear, chemical and petroleum industries propelled intense research activity on the area. Their efforts h
3、ave been aimed at the demystification of the mechanisms taking place during this complex flow situation.In the petroleum industry, two-phase flow can be found in a variety of situations. The three more common working fluids (oil, natural gas and water) can have four different two-phase flow permutat
4、ions: gasliquid, liquidliquid, solidliquid and solidgas flows. A solid phase can be incorporated to the flow either from the reservoir itself (due to either drilling activities or sand formation during production) or from the formation of complex solid structures due to the prevailing production con
5、ditions (e.g. hydrates in natural gas flow or waxes and asphaltenes in oil flow). Oil and natural gas transportation typically deals with a gasliquid system of flow. Due to the deformable nature of fluids, the simultaneous flow of gas and liquid in a pipe represents a very complex process. As a cons
6、equence of their deformable nature, gas and liquid may adopt a wide variety of spatial configurations, usually referred to as flow patterns.Multi-phase flow phenomena can be found in a wide range of length scales of interest. Therefore, the most suitable approach to study multi-phase flows will larg
7、ely depend on the length scale of interest. Typically, in the petroleum industry, attention is given to large-scale phenomena in multi-phase flows, as no detailed flow behaviour is needed for routine design and operation. For instance, in pipeline networks we are interested only in the pressure drop
8、 and liquid hold-up. Other than the effect of the local flow pattern variables, detailed flow phenomena are not important. However, small-scale studies of multi-phase flows are very important because large-scale phenomena are controlled by small-scale physics. For instance, the transition from one f
9、low pattern to another is driven by local small-scale phenomena. One of the most important problems to be addressed by the scientific community is the development of an improved understanding of transitions from one flow regime to another. This can be achieved only through small-scale studies of mul
10、ti-phase flows. In addition, for the improved understanding of the operation of process equipment such as separators in the petroleum industry, it is necessary to understand the small-scale phenomena associated with separation.1.1 The Growth of Multi-phase Flow ModellingThe development of multi-phas
11、e flow large-scale analysis in the petroleum industry has been divided into three partially overlapping periods the empirical period, the awakening years and the modelling period1 which together encompass the second half of the past century. During the empirical period, all efforts were focused on c
12、orrelating data from laboratory and field facilities in an attempt to encompass the widest range of operational conditions possible. The earliest attempt to empirically predict two-phase flow pressure drops for horizontal pipes is the well-known work of Lockhart and Martinelli. This correlation was
13、followed by an innumerable number of new ones, which claimed to be progressively more applicable for a wider range of operational conditions. Being the first quantitative approach to two-phase flow modelling, Lockhart and Martinellis correlation became a classic against which subsequent correlations
14、 were compared. The fact is that most correlations are always best applicable for the conditions from which they were derived. It is worth mentioning the correlation developed by Beggs and Brill for predicting flow behaviour in inclined pipes. Along with a number of modifications applied to it, Begg
15、s and Brills correlation became one of the most extensively used correlations. The correlation considers horizontal, vertical and inclined pipes, and the basic correlating parameter was the Froude number a dimensional number that is considered a measure of the influence of gravity on fluid motion. I
16、n general, the reliance on the empirical approach was always limited by the uncertainty of their application to systems operating under different conditions than those from which the correlations were originally proposed. Nonetheless, calculating and designing flow lines in multi-phase production fa
17、cilities on the basis of empirical correlations was the norm until well into the 1980s.The advent of the personal computer during the 1980s dramatically enhanced the capabilities of handling progressively more complex design situations, which is why this period has been called the awakening years.1
18、Much of the petroleum research on multi-phase flow during these years and the subsequent modelling period was enriched by the progress already made by the nuclear industry. Although the nuclear industry dealt with much simpler fluids (water and steam), it led the way towards more involved two-phase
19、flow analysis in the petroleum industry. More fundamental multi-phase flow analysis approaches, such as two-fluid modelling, were already in use in the nuclear industry in the 1970s. These seed efforts are the genesis of the well-known fast transient two-phase-flow codes RELAP4, RELAP5, RETRAN, MEKI
20、N, COBRA, CATHARE and TRAC in use today in the nuclear industry. Nowadays, the petroleum industry might be ready to explore new research avenues in multi-phase flow analysis, with the incorporation of the increasingly sophisticated modelling tools that have become available in the last few years.The
21、 modelling period, which extends up to the present day, refers to the growing tendency of introducing more physically based (mechanistic or phenomenological) approaches into multi-phase flow calculations. The main goal remains an attempt to reduce the impact of empirical correlations on multi-phase
22、predictions. State-of- the-art multi-phase modelling efforts can be studied in two different but interrelated fields of interest: small-scale and large-scale, depending on the length scale of interest to the modeller. During recent years, the oil and gas industry has paid particular attention to lar
23、ge-scale modelling of multi-phase flows. However, small-scale modelling promises to bring important physical insights into the quest for more accurate and reliable modelling of multiphase flow in the oil and gas industry in the foreseeable future.1.2 Large-scale InterestState-of-the-art large-scale
24、multi-phase flow modelling in the oil and gas industry is largely based on mechanistic models. One of the distinguished features of a mechanistic model is the need for a reliable tool for the prediction of flow pattern transitions for a given set of operational conditions. Perhaps the earliest attem
25、pt to introduce a fully phenomenological description of how transitions occur among the different flow patterns was the work developed by Taitel and Dukler, which focused on horizontal and near horizontal pipes. The work of Taitel and Dukler is considered one of the classic papers in multi-phase pre
26、dictions that began to incorporate more physical insight into analysis in the petroleum industry. This work led the way for subsequent research in the area, and most of their transition criteria are still in use in more recent two-phase flow models. Few years after that initial work, Taitel and co-w
27、orkers extended the model for the vertical and near vertical case and Barnea extended the phenomenological approach to the whole range of pipe inclinations in the 1980s. These three works are commonly referenced among researchers in the area, with a number of attempts at improvement.Additional stead
28、y-state comprehensive mechanistic models for two phase flow in vertical wells, horizontal pipes and deviated wells were presented by Ansari, Xiao, Kaya and co-workers in the 1990s. All these mechanistic models were developed at the Tulsa University Fluid Flow Projects and are usually referred to as
29、TUFFP models. Nowadays, there are also a number of commercially available two phase flow packages, which include various features intended to accomplish specific tasks. Examples include OLGA, TACITE, PEPITE and PIPESIM, among others.Modern multi-phase flow analysis models the flow of oil and gas thr
30、ough pipelines by invoking the basic principles of continuum mechanics and thermodynamics. Depending on how these equations are applied and how the interactions between phases are described, the most widely used two-phase models are the homogeneous model (flow treated as a single phase with averaged
31、 fluid properties), drift-flux model (flow described in terms of an averaged local velocity difference between the phases), separated model (phases considered to be flowing in separated zones of the channel) and two-fluid model (a multi-fluid model that considers two flowing phases and their interac
32、tions).In the last decade, a great deal of attention has also been devoted to mechanistic or phenomenological models i.e. models trying to capture specific features of individual flow patterns in which simplified conservation equations are invoked while the main focus is the prediction of pressure d
33、rop and hold-up. However, in previous decades, the challenge of modelling two-phase flows by invoking such fundamental laws had been circumvented by reliance on empirical and semi-empirical correlations, especially in the oil industry.Perhaps one of the most fundamental and rigorous approaches to th
34、e study of large-scale multi-phase flow currently in use in the petroleum industry is the two-fluid model. In the two-fluid model, separate conservation equations (mass, momentum and energy) are written for each of the two phases for a total of six equations. These equations are coupled with terms d
35、escribing the interaction between phases. In this two-phase flow method of analysis, as well as in all the others, empiricism cannot be completely avoided, since additional closure relationships are needed. Empiricism comes into the picture during attempts to model the variety of constitutive relati
36、onships that show up in conservation equations. For instance, Ayala et al.2 have presented a unified two-fluid model for the analysis of natural gas flow in pipeline in multi-phase flow regimes. Their formulation assumes that both gas and its condensate are a continuum and invokes the basic laws of
37、continuum mechanics in one dimension coupled with a thermodynamic phase behavior model. In their work, the required semi-empirical relationships needed to give mathematical closure to the model are discussed in detail.1.3 Small-scale Interest and Computational PhysicsThe study of small-scale multi-p
38、hase flow has proved to be extremely difficult for researchers due to the elusive nature of the phenomena and the inherent limitations of experimental set-ups. A great deal of progress has been made on the development of useful small-scale experimental studies, but numerical experiments or models st
39、ill remain the most effective way of studying such detailed flow behaviour. The challenge of modelling small-scale multi-phase flow resides in the finite nature of the computer power typically available to the modeller and the difficulty of tracking separated phases (and interfaces between them) wit
40、h sharply different properties. The interplay of these two factors has historically limited the complexity of the systems that can be studied using small-scale simulation. However, during the last decade, major progress has been achieved by implementing a variety of numerical techniques, which typic
41、ally depend upon the flow pattern type that prevails under the conditions of the study. The study of small-scale phenomena started when a group of scientists at the Los Alamos National Laboratory began to develop the basis of Computational Fluid Dynamics (CFD) in the early and mid-1960s. In multi-ph
42、ase flow modelling within small-scale interest, the Navier-Stokes equations with the appropriate boundary conditions are solved through a suitable numerical method e.g. finite volumes, finite differences, finite elements or spectral methods. The main problem arises when considering that some boundar
43、y conditions are time-dependent, since they are located at phase boundaries, which are free to move, deform, break up or coalesce. Different methods have been proposed; here we mention a few of them.The most common small-scale modelling approach discretises the flow domain using a regular and statio
44、nary grid i.e. the well-known Eulerian frame of reference for fluid motion. The first small-scale Eulerian method proposed was the marker-and-cell (MAC) method, where marker particles distributed uniformly in each fluid were used to identify each fluid. Using this method, in the late 1960s Harlow an
45、d Shanon studied the splash when a drop hits a liquid surface. The MAC method has become obsolete since then and has largely been replaced by others that use marker functions instead e.g. the so-called volume-of-fluid (VOF) method. In the VOF method, the transition between two fluids takes place wit
46、hin the context of one grid cell. The main problem associated with this is the difficulty of maintaining a sharply defined boundary between two flowing fluids. In order to address this difficulty, level-set (LT) methods use continuous rather than discontinuous marker functions in order to identify t
47、he fluids. The use of continuous marker functions creates smooth transition zones between the two fluids of interest and avoids the difficulty of maintaining a sharply defined boundary.Some other small-scale modelling approaches use the Lagrangian frame of reference for fluid motion. In Lagrangian m
48、ethods, the numerical grid follows the fluid and deforms with it. In this approach, the motion of the fluid interface needs to be modelled in order to accurately capture the new fluid positions at each time-step. At every time-step, the grid is refitted and adjusted to match the location of the new,
49、 displaced boundaries. In the 1980s, Ryskin and Leal used this method to study the steady rise of buoyant, deformable, axisymmetric bubbles, while Oran and Boris studied the break-up of a two-dimensional drop. A similar approach, called front tracking, is also used, where a separate front marks the interface but a fixed grid is used for the fluid within each phase; however, the fixed grid is modified near the front so a single grid line follows the interfac