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scheme that uses a finite-volume technique24 25 to simulate difficult geometries and features (faults, horizontal wells, and irregular boundaries) that do not follow the standard Cartesian orthogonality of other simulators. In addition, because the grid is based on perpendicular bisectors, it is particularly suited for use within windows of interest, with standard Cartesian grids used outside these windows.

Our first task was to compare the numerical results with well-known analytical solutions to assess the reliability of the simulation model in general and to determine how it would apply to horizontal-well cases. An infinite-acting reservoir saturated with a single fluid and having a fully penetrating vertical well, was simulated for constant production rate. The numerical results agreed with the line-source solution to four digits.

For the specific simulation of horizontal wells, a constant-pressure outerboundary ellipse was used with the half-axis of the ellipse,, related to the well length. The permeability anisotropy between the horizontal and vertical planes was handled by use of multiplication factors to account for the transmissibility of each gridblock. A constant-pressure outer boundary was modeled (with grid points exactly on the boundary) to represent the drainage ellipse of the horizontal well. Simulations were done until steady state was established, and constant pressure was maintained at the well.

Efforts to improve the accuracy of the numerical solution (e.g., adding more vertical layers and diminishing the horizontal block size) showed that the numerical solution could not converge to Joshi's formula. The considerable differences, especially in highly anisotropic cases, made it necessary to investigate the reason for these discrepancies.

Recompletion and Remedial Workovers

It was originally thought unlikely that it would be necessary to work over or recomplete a horizontal well; however, due to the heterogeneity of many "homogeneous" reservoirs and the tendency for natural fractures within a reservoir to extend into either the gas cap or water zone, today there is a much greater need for a completion which will allow for the well to be worked over and or recompleted. Conventional retrievable service tools, as well as coiled tubing conveyed tools, have been developed to enable horizontal wells to be worked over and recompleted.

Coiled tubing technology has been developed to service horizontal wells, without the requirement of having a rig on location, or can be used to log and perforate a well. Coiled tubing conveyed versions of conventional wireline tools, with pump-through capability, are available to permit conventional wireline operations to be performed quickly and efficiently in a horizontal

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wellbore. Selective zone stimulation or isolation is also possible using coiled- tubing-conveyed inflate straddle packers and bridge plugs.

These recent developments mean that the mechanical aspects of a horizontal well completion are no longer the constraining factor. It is now possible to perform any of the services which can be performed in a vertical wellbore equally well in a horizontal wellbore.

Summary

There would now appear to be general agreement within the industry that there is a need for wellbore segmentation, using cement inflate packers or fully cemented liners, to compensate for the natural heterogeneity of most reservoirs and the need for the following during the life of the well.

•Zone Isolation

•Stimulation

•Gas and Water Shutoff

•Reservoir Monitoring

•Cost

Although an "ideal" horizontal well completion has yet to be found.

SELECTING THE RIGHT COMPLETION

Introduction

Once it has been determined that horizontal wells provide the most costeffective solution to developing a specific reservoir, it is still necessary to carefully consider which type of completion will ensure that the full potential of the reservoir can be realized. Unlike a vertical well an inappropriate completion may more than offset the advantages of drilling the horizontal hole section.

Many of the early horizontal wells were completed openhole or with slotted liners and the performance of these wells has, in many cases, proved to be very good. However, it has also highlighted some of the problems and limitations associated with these completions as well as demonstrating how, by selecting a different type of completion, horizontal wells can be used to maximize production from a number of different, previously marginal reservoirs. Outlined below is a review of points, which need to be considered when, choosing how to complete a horizontal well.

Economics

Many of the early horizontal wells were drilled by operators as pilot wells simply to determine their feasibility and cost. Therefore, these wells represented

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a calculated financial risk; the short-term ROI played a major role in selecting the type of completion which was used, openhole or slotted liners.

Now that the technique has become established, the concern is no longer to recover the cost of drilling and completing the well, but rather to maximize the total recovery and useful life of the well, including remedial workovers, recompletion, and stimulation treatments.

Difficult wells require new well control procedure

The development of new software tools and downhole sensors has led to a better understanding of dynamic conditions in the wellbore, allowing drillers to make fundamental changes in the way they approach well control.

Before these technologies became available, however, the complexity of multiphase flow forced drilling personnel largely to ignore conditions in the annulus. In its place, very simple assumptions, based solely on drill pipe pressure, had to be made.

Yet today, drilling near the "edge" - with smaller tolerances between mud weights and fracture pressures, typically prevalent in high pressure, deepwater, and underbalanced wells - no longer affords drilling professionals the luxury of discounting this information.

This article shows how improvements in the understanding of events in the annulus can be incorporated into a simple and cost-effective, well control program for a "more difficult" well. The example given, which compares the "new well control" and "weight and wait" methods, provides a look at a deepwater Gulf of Mexico well drilled with synthetic-base mud.

Different variations of the new well control procedure, for example an equivalent of the "driller's" method, would be used in other circumstances. It should be noted, however, that for wells where the tolerances are sufficient, the continued use of conventional well control methods can be supported.

Two very significant improvements have occurred in drilling technologies, which can now lead to a safer, more economic operation:

1.Development of fully dynamic well-control simulation software and spreadsheet front-end applications capable of modeling multiphase annular flow, real reservoir fluids, and gas dissolution in oil-base mud.

2.Combined use of pressure while drilling and transient hydraulictemperature models. In this case, rheologies based on downhole temperature and pressure readings can pinpoint static and circulating annulus pressures.

The net effects of this new well control procedure include the following advantages:

•Greatly reduced risk for a serious well control incident;

•Improved understanding and control throughout a well control incident;

•Improved safety;

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•Greatly reduced potential for lost circulation;

•Improved drilling effectiveness and reduction of overall drilling costs.

In particular, the goal for the new procedure is safely to circulate out gas without losing returns once a kick has been detected. Unfortunately, this goal is not always attainable using conventional well control methods.

The Completion Within an Anisotropic Formation

The horizontal hole section is usually drilled within a single formation, usually the reservoir, and so it was often presumed, based on information obtained from offset vertical wells, that the reservoir would be homogeneous and, therefore, there would be no requirement for zonal isolation or segmentation.

As so often in the history of the petroleum industry, the development of any new technique is one of trial and error. In this case, it is greatly complicated by the lack of any technique that can predict the exact morphology of the reservoir away from the immediate vicinity of the wellbore. Experience has shown that many supposedly homogeneous reservoirs are in fact heterogeneous along their horizontal axis.

It is this inability to predict the exact nature of the reservoir through which a horizontal borehole will be drilled that has proved to be the limitation of openhole and slotted liner completions. In many cases small faults, microfractures, and horizontal heterogeneity, such as vertical chimneys of dissolved coral in otherwise homogeneous reservoirs, have resulted in water and gas coning or production being confined to certain intervals along the wellbore. It is also the reason why, in many cases, it is now considered essential to complete a horizontal well so that zonal segmentation is possible along the wellbore.

Fractured Reservoirs

Many wells have been drilled intentionally to intercept natural fractures in the reservoir, e.g. in the Austin chalk and Rospo Mare reservoirs. It was hoped that this would eliminate the need for stimulation treatments and the requirement for segmentation of the wellbore.

Although this is fundamentally correct there are an increasing number of cases reported where it now thought that zonal segmentation would have been beneficial. This is either due to intersecting fracture with varying reservoir pressure or where some of the fractures prematurely start to produce water or gas. Also, natural fractures are often severely damaged while drilling and completing the well and must be selectively treated to restore natural productivity.

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Cementing and Perforating

Initially operators were unsure of whether or not it was feasible to run and cement a conventional liner in a horizontal wellbore. The potential cost of failing to either get the liner in place or satisfactorily cemented was an even greater deterrent than the additional cost of cementing and perforating a liner.

Now a number of operators, Maersk Oil and Gas, Shell, and BP, are running and cementing liners in horizontal hole sections on a routine basis, and most operators are confident that it is realistic to expect to be able to run and cement liners in a horizontal wellbore.

It has also often been taken for granted that if a well was completed with a fully cemented liner it would then be necessary to perforate the entire length to have the equivalent production of an openhole or slotted liner completion. Goode and Wilkinson (1989) showed that, in many cases, it is only required to selectively perforate 50% of the length of the horizontal wellbore to obtain between 60% and 95% of the production possible with an openhole completion.

The fraction of the wellbore which must be perforated to have the equivalent of openhole production is a function of dimensionless reservoir

The same approach can also be taken to determine if any reduction in well potential would take place as a result of installing external casing packers at intervals along the casing to provide some degree of zonal segmentation.

10) Информационные технологии

Basic features of database programs

With a database you can store, organize and retrieve a large collection of related information on computer. If you like, it is the electronic equivalent of an indexed filing cabinet. Let us look at some features and applications of a computer database:

• Information is entered on a database via fields. Each field holds a separate piece of information, and the fields are collected together into records. For example, a record about an employee might consist of several fields, which give his/her name, address, telephone number, age, salary, and length of employment with the company. Records are grouped together into files, which hold large amounts of information. Files can easily be updated: you can always change fields, add new records or delete old ones. With the right database software, you are able to keep track of stock, sales, market trends, orders, invoices and many more details that can make your company successful.

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• Another feature of database programs is that you can automatically look up and find records containing particular information. You can also search on more than one field at a time. For example, if a managing director wanted to know all the customers that spend more than £7,000 per month, the program would search on the name field and the money field simultaneously.

If we had to summarize the most relevant advantages of a database program over a card index system, we would say that it is much faster to consult and update, occupies a lot less space, and records can be automatically sorted into numerical or alphabetical order using any field.

The best packages also include networking facilities, which add a new dimension of productivity to businesses. For example, managers of different departments can have direct access to a common database, which represents an enormous advantage. Thanks to security devices, you can share part of your files on a network and control who sees the information. Most aspects of the program can be protected by user-defined passwords. For example, if you wanted to share an employee's personal details, but not his commission, you could protect the commission field.

Other features like mail merging, layout design and the ability to import and export data are also very useful. In short, a database manager helps you control the data you have at home, in the library or in your business.

Computer graphics

Computer graphics are pictures and drawings produced by computer. A graphics program interprets the input provided by the user and transforms it into images that can be displayed on the screen, printed on paper or transferred to microfilm. In the process the computer uses hundreds of mathematical formulas to convert the bits of data into precise shapes and colours. Graphics can be developed for a variety of uses including presentations, desktop publishing, illustrations, architectural designs and detailed engineering drawings.

Mechanical engineers use sophisticated programs for applications in computer-aided design and computer-aided manufacturing. Let us take, for example, the car industry. CAD software is used to develop, model and test car designs before the actual parts are made. This can save a lot of time and money Computers are also used to present data in a more understandable form: electrical engineers use computer graphics to design circuits and people in business can present information visually to clients in graphs and diagrams. These are much more effective ways of communicating than lists of figures or long explanations.

Today, three-dimensional graphics, along with colour and animation are essential for such applications as fine art, graphic design, computer-aided

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engineering and academic research. Computer animation is the process of creating objects and pictures which move across the screen; it is used by scientists and engineers to analyse problems. With the appropriate software they can study the structure of objects and how it is affected by particular changes.

Basically, computer graphics help users to understand complex information quickly by presenting it in a clear visual form.

Programming languages

Unfortunately, computers cannot understand ordinary spoken English or any other natural language. The only language they can understand directly is called machine code: central processors operate on codes, which consist of a series of binary digits (Is and Os). In this form, the instructions are said to be in machine code.

However, machine code as a means of communication is very difficult to write. For this reason, we use symbolic languages that are easier to understand. Then, by using a special program, these languages can be translated into machine code. For example, the so-called assembly languages use abbreviations such as ADD, SUB, MPY to represent instructions. These mnemonic codes are like labels easily associated with the items to which they refer.

Basic languages, where the program is similar to the machine code version, are known as low-level languages. In these languages, each instruction is equivalent to a single machine code instruction, and the program is converted into machine code by a special program called an assembler. These languages are still quite complex and restricted to particular machines.

To make the programs easier to write and to overcome the problem of intercommunication between different types of machines, higher-level languages were designed such as BASIC, COBOL, FORTRAN or PASCAL. These languages are all problem-oriented rather than machine-oriented and can all be converted into the machine codes of different types of computers. Programs written in one of these languages (known as source programs) are converted into a lower-level language by means of a compiler (generating the object program). On compilation, each statement in a high-level language is generally translated into many machine code instructions.

People communicate instructions to the computer in symbolic languages and the easier this communication can be made the wider the application of computers will be. Scientists are already working on Artificial Intelligence and the next generation of computers may be able to understand human languages.

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COMPUTER GAMES IN EDUCATION

(1) Computer games have come a long way since Pong, a high tech version of table tennis, became the first to hit the screen in 1972. The vast majority of children now regularly play games ranging from ND Mario to Mortal Kombat. One study has suggested that one teenager in fifteen devotes thirty hours a week to them, though the majority are moderate consumers.

What does it do to young minds?

For years concern has been expressed by parents and teachers about the effect of computer games on the moral and mental make-up of the next generation. Some have warned that a relentless diet of whizz-bang 'shoot-'em- ups' fosters antisocial behavior, even playground violence. Others believe that the age of the zombie is upon us.

But expert opinion is shifting radically. Psychologists in America and Britain now suggest that while computer games hold some dangers for children, they also provide opportunities their parents never enjoyed to amplify powers of concentration and memory. Researchers have also highlighted (2) the positive response of children to the way computer games reward success, thereby spurring them on to look for greater challenges-a boon if the same attitude is applied to school work. A leading academic at the University of Washington has even claimed that (3) children think differently when they play computer games, learning to deal with problems in parallel rather than in sequence. In effect, children are being trained to tackle problems in a fashion which is not only more rapid but also more effective. In the long term, (4) the facility that game players develop with computer graphics could help much in future career. It could, for example, be of particular benefit to children who go on to become engineers or scientists.

(5) Games are also now being developed for pre-school children to encourage reading and writing skills. At Lanterns, a private nursery in east London, computer games make up part of the syllabus. Each week its sixteen pupilsthe youngest aged two-are treated to a whirlwind tour of cyberspace. Every day the pupils attend a special class, such as dance or drama, and on Tuesdays they have a computer workshop where they spend an hour playing games. All the children love it. There is not technophobe among them.

TALKING TO COMPUTERS

One of the shared assumptions in computer research is that talking to computers is a really great idea. Such a good idea that speech is regarded as the natural interface between human and computer.

Each company with enough money to spare and enough egoism to believe that it can shape everyone’s future now has a ‘natural language’ research group.

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Films and TV series set in the future use computers with voice interfaces to show how far technology has advanced from our own primitive day and age. The unwritten assumption is that talking to your house will in the end be as natural as shouting at your relatives.

The roots of this shares delusion lie in the genuine naturalness of spoken communication between humans. Meaning is transferred from person to person so effortlessly that it must be the best way of transferring information from a human to another object.

This view is misguided on many different levels. First people are so good at talking and at understanding what others say because they share a common genetic heritage. Children's brains are hard-wired with a general language structure that their surrounding spoken-word environment. The old view that language is learned by copying parents and other adults has been discredited in recent years, to be replaced by the theory that words are attached to a way that grammar ‘emerges’, as it were, rather than is taught.

This view of human language, added to shared human experience, shows how people understand each other precisely in a conversation where a transcript would make little sense. Unfinished sentences, in-jokes, catchphrases, hesitation markers like 'er' and 'you know', and words whose meaning is only clear in the context of that one conversation are no bar to human understanding, but baffled early attempts at computer speech recognition.

Recent advances in artificial intelligence address the problem but only in part. Pioneering linguistic research by scientists has revealed much of the underlying structure of human language, that programmers can now mimic that structure in their software and use statistical and other techniques to make up for the lack of shared experience between operator and machine.

Some of the obvious drawbacks of universal voice control have already been countered. The dreadful prospect of an office full of people talking to their machines has brought about the headset and the throat microphone; these also address the fact that people feel ridiculous talking to something which is nonhuman. The increasing sophistication of voice-processing and linguisticanalysis tools cuts out the dangers of inaccurate responses to input, preventing the computer from having to respond to every single word uttered, no matter how nonsensical in the overall context.

The fundamental objection to natural language interfaces is that they’re about as unnatural as you can get. You might be able to order a computer about in its limited sphere of action, but it’ll never laugh at your jokes, make sarcastic comments, volunteer irrelevant but interesting information or do any of the other things that make real human conversation so fascinating. If interaction is limited to didactic instruction from human to computer, why use up valuable processing time performing the immensely difficult task of decoding language correctly? To keep your hands free? For what, precisely?

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There’s another psychological reason why language control is difficult: the decline in domestic service throughout this century, the absence of military experience from the lives of the last two generations, and the flattering out of business management have all combined to produce a population that's not accustomed to giving crisp orders and expecting them to be obeyed.

Controlling a computer by word power works beast if you imitate a drill sergeant, avoiding all ‘could you’s’ and ‘would you mind’s’ that most of us use when trying to make someone to do something they’d rather not do. This modern variant of the servant problem opens up the chance of ambiguity and error when interacting with a machine.

It could be said, though, it's just as well as we’ve forgotten how to give orders. Slaves always have had a reputation for conspiring against their master’s backs.

WILL OUR CHILDREN READ BOOKS?

Before describing the hierarchy of the arts in the 21st century, it is sensible to recall the experts’ forecast for the 20th century. The headline stories were the rise of cinema and then television. And these successes, it was assumed, would mean failure for older forms of entertainment and information. Since the 1950s, commentators have regularly predicted that these two new visual giants would eventually destroy theatre, radio, newspapers and books by taking over the functions of these earlier forms or eroding the time available for enjoying them.

In fact, despite the advent of multi-channel, 24-hour TV and multi-screen movie theatres, it can be said that only two cultural forms have died in the past 100 years — music hall and the letter — and the second of these was killed, not by television but by the telephone, before, in the strange way of these things, being somewhat restored by the inventions of the fax machine and e-mail. So the cultural story of the 20th century — an epoch of electronic invention and mechanical radicalism — has unexpectedly been that of the durability of traditional and particularly printed forms.

Looking forward then, we should be aware of pessimism's poor record. The book, for example, seems as obvious a candidate for redundancy now as it has since the middle of the 20th century. Where people previously assumed that tele-literacy would finish reading, they now point to computer literacy as the executioner. Yet the book, to an extraordinary degree, has learned to coexist with its visual rivals.

Most Hollywood projects derive from novels: often trashy ones, it is true, but also the classics. And not only do movies and television series descend from books, but almost routinely, they return to them as nearly every screen product has its in book. It all suggests that the desire of the viewer to follow the visual experience with a print experience is even more tenacious than ever.