1、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 日中国石油大学（华东）本科毕业设计（论文）外文翻译1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
2、 as the 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 effo
3、rts have 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 per
4、mutations: 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 productio
5、n conditions (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
6、 consequence 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
7、 largely depend on the length scale of interest. Typically, in the petroleum 中国石油大学（华东）本科毕业设计（论文）外文翻译2industry, 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 intere
8、sted only in the pressure drop 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 insta
9、nce, the transition from one flow 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 thro
10、ugh small-scale studies of multi-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 Modellin
11、gThe development of multi-phase 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,
12、 all efforts were focused on correlating 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 Mar
13、tinelli. This correlation was 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 中国石油大学（华东）本科毕业设计（论文）外文翻译3Martinellis correlation
14、 became a classic against which subsequent correlations 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. A
15、long with a number of modifications applied to it, Beggs 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
16、 measure of the influence of gravity on fluid motion. In 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, calculatin
17、g and designing flow lines in multi-phase production facilities 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
18、 why this period has been called the awakening years.1 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
19、steam), it led the way towards more involved two-phase 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 tran
20、sient two-phase-flow codes RELAP4, RELAP5, RETRAN, MEKIN, COBRA, CATHARE and TRAC in use today in the nuclear industry. 中国石油大学（华东）本科毕业设计（论文）外文翻译4Nowadays, the petroleum industry might be ready to explore new research avenues in multi-phase flow analysis, with the incorporation of the increasingly so
21、phisticated modelling tools that have become available in the last few years.The 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 r
22、emains an attempt to reduce the impact of empirical correlations on multi-phase 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. Du
23、ring recent years, the oil and gas industry has paid particular attention to large-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
24、 in the foreseeable future.1.2 Large-scale InterestState-of-the-art large-scale 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 t
25、ransitions for a given set of operational conditions. Perhaps the earliest attempt 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
26、 of Taitel and Dukler is considered one of the classic papers in multi-phase predictions 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
27、recent two-phase flow 中国石油大学（华东）本科毕业设计（论文）外文翻译5models. Few years after that initial work, Taitel and co-workers 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 com
28、monly referenced among researchers in the area, with a number of attempts at improvement.Additional steady-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 mech
29、anistic models were developed at the Tulsa University Fluid Flow Projects and are usually referred to as 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, TAC
30、ITE, PEPITE and PIPESIM, among others.Modern multi-phase flow analysis models the flow of oil and gas through 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
31、most widely used two-phase models are the homogeneous model (flow treated as a single phase with averaged 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
32、the channel) and two-fluid model (a multi-fluid model that considers two flowing phases and their interactions).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
33、 which simplified conservation equations are invoked while the main focus is the prediction of pressure drop and 中国石油大学（华东）本科毕业设计（论文）外文翻译6hold-up. However, in previous decades, the challenge of modelling two-phase flows by invoking such fundamental laws had been circumvented by reliance on empirical
34、 and semi-empirical correlations, especially in the oil industry.Perhaps one of the most fundamental and rigorous approaches to the 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,
35、momentum and energy) are written for each of the two phases for a total of six equations. These equations are coupled with terms describing 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 addition
36、al closure relationships are needed. Empiricism comes into the picture during attempts to model the variety of constitutive relationships 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 m
37、ulti-phase flow regimes. Their formulation assumes that both gas and its condensate are a continuum and invokes the basic laws of continuum mechanics in one dimension coupled with a thermodynamic phase behavior model. In their work, the required semi-empirical relationships needed to give mathematic
38、al closure to the model are discussed in detail.1.3 Small-scale Interest and Computational PhysicsThe study of small-scale multi-phase 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 de
39、al of progress has been made on the development of useful small-scale experimental studies, but numerical experiments or models still remain the most effective way of studying such detailed flow behaviour. The challenge of modelling small-scale multi-中国石油大学（华东）本科毕业设计（论文）外文翻译7phase flow resides in th
40、e finite nature of the computer power typically available to the modeller and the difficulty of tracking separated phases (and interfaces between them) with sharply different properties. The interplay of these two factors has historically limited the complexity of the systems that can be studied usi
41、ng small-scale simulation. However, during the last decade, major progress has been achieved by implementing a variety of numerical techniques, which typically depend upon the flow pattern type that prevails under the conditions of the study. The study of small-scale phenomena started when a group o
42、f 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-phase flow modelling within small-scale interest, the Navier-Stokes equations with the appropriate boundary conditions are solved through a suitabl
43、e numerical method e.g. finite volumes, finite differences, finite elements or spectral methods. The main problem arises when considering that some boundary conditions are time-dependent, since they are located at phase boundaries, which are free to move, deform, break up or coalesce. Different meth
44、ods 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 stationary grid i.e. the well-known Eulerian frame of reference for fluid motion. The first small-scale Eulerian method proposed was the marker-and-cel
45、l (MAC) method, where marker particles distributed uniformly in each fluid were used to identify each fluid. Using this method, in the late 1960s Harlow and 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 oth
46、ers that use marker functions instead e.g. the so-called volume-of-fluid (VOF) method. In the VOF method, the transition between two fluids 中国石油大学（华东）本科毕业设计（论文）外文翻译8takes place within the context of one grid cell. The main problem associated with this is the difficulty of maintaining a sharply defin
47、ed 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 the fluids. The use of continuous marker functions creates smooth transition zones between the two fluids of interest and
48、 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 methods, the numerical grid follows the fluid and deforms with it. In this approach, the motion of the fluid interface ne
49、eds 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, 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
