Chapter VIII rotary drilling bits

EXERCISE 1 Read and translate the text, using the words after the text.

Rotary drilling bits may be drag bits and rolling cutter bits. All drag bits consist of fixed cutter blades that are integral with the body of the bit and rotate as a unit with the drill string. Rolling cutter bits have two or more cones containing the cutter elements which rotate about the axis of the cone as the bit is rotated at the bottom of the hole.

Drag bits may be bits with steel cutters, diamond bits and polycrystalline diamond bits. An advantage of drag bits over rolling cutter bits is that they do not have any rolling parts. Since drag bits can be made of one solid piece of steel, there is less chance of bit breakage, which would leave junk in the bottom of the hole. Drag bits such as fishtail bits perform best in uniformly soft formations. Diamond bits perform best in non-brittle formations. Polycrystalline diamond bits (PCD bits) have drill blanks consisting of a layer of synthetic poly-crystalline diamond about 1/64 inches thick. They perform best in soft, firm and medium hard, non-abrasive formations that are not «gummy»,

Important design features of a PCD bit are the bit shape or crown profile, the size, shape and number of cutters used and the angle of attack between the cutter and the surface of the exposed formation. Cutter orientation is defined in terms of back-rake, side rake and chip clearance or cutter exposure.

Rolling cutter bits

The three-cone rolling cutter bit is the most common type now used in rotary drilling operations. The general type may have a large variety of tooth design and bearing types and thus is suited for a wide variety of formation characteristics. The three cones rotate about their axis as the bit is rotated on the bottom. The largest limitation in their design is that the bit must fit inside the borehole. It is necessary to maximum use of a very limited space.

The drilling effect of a rolling cutter bit depends on the offset of the cones. The offset of a bit is a measure of how much the cones are moved so that their axis does not intersect at a common point of the center line of the hole.

The shape of the bit tooth also has a large effect on the drilling action. Long widely spaced steel teeth are good for drilling soft formations. While drilling rock, the tooth length and cone offset must be reduced to prevent tooth breakage.

Standard classification of bits

This classification is a three-digit code. The first digit is the bit series number. The letter D before the first digit means the bit is diamond or PCD drag bit. Series D1 to D5 are reserved for diamond bits in the soft, medium soft, medium, medium hard and hard formations respectively. The second digit is the type number. Type O is for PCD drag bits. Types 1-4 designate a formation hardness classification. Feature numbers are interpreted differently, depending on the general type of bit being described.

Eight standard diamond and PCD drag bits features are: step-type profile, long taper profile, short taper profile, non-taper profile, down-hole motor type, side-track type, oil-base type, core-ejector type. The remaining feature (9) is reserved for special features.

The words to be memorized:

1. bottom of the hole - забой

2. drag bit – лопастное долото

3. rolling cutter bit – шарошечное долото

4. blade - лопасть, лезвие

5. integral - цельный

6. body - корпус

7. cone - конус, шарошка

8. axis - ось

9. cutter – режущий элемент, резец

10. solid - сплошной, цельный

11. breakage - поломка

12. junk – металлические обломки, мусор

13. fish tail bit – долото типа «рыбий хвост»

14. uniformly - однородный

15. non-brittle - неломкий, нехрупкий

16. design - конструкция

17. blank - покрытие, слой

18. non-abrasive - неабразивный

19. gummy - липкий, налипающий

20. angle of attack – угол атаки

21. rake – угол резания

22. cutter exposure – величина выступа резца

23. crown profile – профиль шарошки

24. exposed formation - обрабатываемая порода

25. cutter orientation - направления расположения резцов

26. back-rake – наклоненный назад

27. side-rake – наклоненный в бок

28. chip clearance - зазор для выбуренной породы

EXERCISE 2 Answer the following questions.

1. What do all drag bits consist of?

2. What do rolling cutter bits consist of?

3. What is the advantage of drag bits over rolling cutter bits?

4. What are important design features of a РСD bit?

5. What is the most common type used in rotary drilling operations?

6. What does the drilling effect of a rolling cutter bit depend on?

7. While drilling rock, the tooth length and cone offset must be reduced to prevent tooth breakage, mustn’t they?

8. What is standard classification of bits?

9. How are feature numbers interpreted?

10. Is the remaining feature reserved for special features?

EXERCISE 3 Find the proper Russian equivalent to the given English ones.

1. cone 1. неломкий

2. axis 2. режущийэлемент

3. non-brittle 3. Металлические обломки

4. blade 4. липкий

5. cutter 5. профиль шарошки

6. gummy 6. угол резания

7. junk 7. ось

8. rake 8. покрытие, слой

9. crown profile 9. лопасть

10. blank 10. шарошка

EXERCISE 4 Complete the sentences.

1. Rotary drilling bits may be…

2. … which would leave junk in the bottom of the hole.

3. Diamond bits perform…

4. Cutter orientation is defined…

5. The three – cone rolling cutter bit…

6. The largest limitation in their design is…

7. … the effects of the cones.

8. …are good for drilling soft formations.

9. While drilling rock…

10. Feature numbers are interpreted…

EXERCISE 5 Translate the sentences from Russian into English.

1. Роторное бурильное долото может быть лопастным и шарошечным.

2. Преимущество лопастного долота над шарошечным в том, что у него нет вращающихся частей.

3. Лопастное долото типа «рыбий хвост», лучше всего подходит для однородных легких пород.

4. ПКА долота наиболее эффективны в мягких, твердых и средне-твердых неабразивных породах.

5. Когда бур вращается на дне скважины, три конуса – шарошки вращаются каждый вокруг своей оси.

6. Так как лопастное долото можно сделать из цельного куска стали, вероятность поломки бура меньше.

7. Трехшарошечное долото – это наиболее распространенный тип, используемый в роторном бурении.

8. Рабочий эффект шарошечного долота зависит от смещения шарошек.

9. Форма зубьев бура также влияет на результаты бурения.

10. Важной характеристикой ПКА долота является форма или профиль шарошки.

EXERCISE 6 Retell the text and discuss in dialogs with your group mates this theme.

EXERCISE 7 Prepare a presentation about rotary drilling bits.

UNIT IV

SUPPLEMENTARY READING

Text 1

Read, translate the text "Oil Business" and make the annotation of it.

Oil Business

Part I

Nowadays speaking about all the activities connected with oil and gas business the petroleum experts use three terms: upstream, midstream and downstream. The term «upstream» means oil and gas exploration, drilling and production, «midstream» means transportation, storage, gas processing and «downstream» means refining, distribution, marketing.

To start the story of oil business one should know something about the origin of petroleum. Most geologists believe that oil is of organic origin, i.e. (that is), it originated from decomposition of mainly marine animals and plants buried under thick layers of mud perhaps as long as 400 - 500million years ago. These deposits rich in organic material became the source rocks (sedimentary rocks) for the generation of crude oil. High temperatures and pressures in the sedimentary rocks caused chemical processes that, in turn, resulted in the formation of a waxy substance called kerogen. When heated to a temperature above 100° С kerogen is separated into a liquid (oil) and gas (natural gas). The chemical composition of petroleum is principally hydrocarbons, although a few sulphur-, nitrogen-, and oxygen-containing compounds are usually present.

To look for and to find petroleum is the art of exploration. According to the theories of petroleum origin sedimentary basins are a prime aim for the oil hunters. In general, to form oil and gas pools the following conditions must be fulfilled. 1) The presence of a "source rock" which geologic history allowed the formation of oil. 2) Migration of the oil from the source rock to a «reservoir rock» that is thick, permeable and porous enough to hold a sizable accumulation of oil. 3) Entrapment. Waters and pressure of overlying layers pushed oil upward until it reached an impermeable layer of rock called a cap rock. A cap rock stops further migration of oil and oil is thus trapped in a reservoir. It is from these reservoirs that people began extracting oil and gas millions of years later.

It should be noted that successful exploration is based on accurate interpretation of the information to be provided by geological and geophysical surveys. Seismic prospect minimizes exploration risk and reduces finding costs. Using complicated tools geologists identify potential traps for oil and gas.

Drilling can prove the presence of oil after the geologists and gee-physicists have found a favorable location for the accumulation of oil. All wells drilled to discover oil and gas accumulations are "exploratory wells", commonly referred to as "wildcats". A successful wildcat is a "discovery well", while an unsuccessful one is a "dry hole".

After oil has been discovered the first wells to be drilled to establish the limits of the field are "appraisal wells". All subsequent wells are "development wells". To determine the reservoir and oil properties geophysical investigations (logging) are to be conducted in the wells. If the first wells "prove" an oilfield, the data from them are used in drawing up plans for the commercial development of the field.