The Basics of Drilling Technology
Deep drilling is far from being a new technology. As early as 600 B.C. Confucius reports that wells have been sunk in China to a depth of about 500m into salt brine with hammer drilling devices. In Europe, both in ancient times and in the Middle Ages, wells were sunk to obtain water and later for prospecting shallow ore lodes. Development of drilling engineering and well depths that could be achieved stagnated for many centuries. The search for raw materials (potash, iron ore, and coal) in the course of the industrialization in the 19th century forced the development of deep drilling engineering. At that time, drilling depths already reached 2000 m.
In Europe during the second half of the 19th century and the start of the 20th century an extensive search for raw materials took place. It was pioneers like Von Oeynhausen, Craelius and Anton Raky who encouraged the progression of deep drilling by, for example, developing high-speed rotary percussion drilling with circulating drilling mud. Only then could the frozen boreholes for shaft sinking of mines for coal and rock salt be produced.
The rotary drilling method, developed in the United States at the end of the 19th century for the exploration and development of oil deposits, was an important step forward. Since then, rotary drilling has been continuously developed and today is still the dominant drilling method by which depths of more than 9000m have been reached in commercial boreholes. The present depth record has been achieved with the Kola SG 3 well in the Commonwealth of Independent States, which reached a depth of 12 261 m, using turbodrilling.
The circulating viscoplastic drilling mud and powerful roller cone drill bits are the most important characteristics of rotary drilling. These, in combination with other typical features, have contributed to the overriding importance of rotary drilling in the exploration and development of deep and high-pressure reservoirs. Spectacular blowouts, which were numerous in the past, are now rare.
Beginning to drill
Once the site has been selected, it must be surveyed to determine its boundaries, and environmental impact studies may be done. Lease agreements for the land must be obtained and evaluated legally. Once the legal issues have been settled, the crew goes about preparing the land:
1. The land is cleared and leveled, and access roads may be built.
2. Because water is used in drilling, there must be a source of water nearby. If there is no natural source, they drill a water well.
3. They dig a reserve pit, which is used to dispose of rock cuttings and drilling mud during the drilling process, and line it with plastic to protect the environment. If the site is an ecologically sensitive area, such as a marsh or wilderness, then the cuttings and mud must be disposed offsite – trucked away instead of placed in a pit.
Once the land has been prepared, several holes must be dug to make way for the rig and the main hole. A rectangular pit, called a cellar, is dug around the location of the actual drilling hole. The cellar provides a work space around the hole, for the workers and drilling accessories. The crew then begins drilling the main hole, often with a small drill truck rather than the main rig. The first part of the hole is larger and shallower than the main portion, and is lined with a large-diameter conductor pipe. Additional holes are dug off to the side to temporarily store equipment – when these holes are finished, the rig equipment can be brought in and set up.
The crew sets up, and starts the drilling operations. First, from the starter hole, they drill a surface hole down to a certain depth, which is somewhere above where they think the oil trap is located. There are five basic steps to begin drilling the surface hole:
Place the drill bit, collar and drill pipe in the hole.
Attach the kelly and turntable and begin drilling.
As drilling progresses, mud circulates through the pipe and out of the bit to float the rock cuttings out of the hole.
Add new sections (joints) of drill pipes as the hole gets deeper.
Remove (trip out) the drill pipe, collar and bit when the pre-set depth (anywhere from a few hundred to a couple-thousand feet) is reached.
Once they reach the pre-set depth, they must run and cement the casing – place casing-pipe sections into the hole to prevent it from collapsing in on itself. The casing pipe has spacers around the outside to keep it centered in the hole.
The casing crew puts the casing pipe in the hole. The cement crew pumps cement down the casing pipe using cement slurry and drill mud. The pressure from the drill mud causes the cement slurry to move through the casing and fill the space between the outside of the casing and the hole. Finally, the cement is allowed to harden and then tested for such properties as hardness, alignment and a proper seal.
The cementing of the casings serves the following purposes:
1) massive bond of casing and formation, in order to divert the forces resulting from the loading of the casing into the formation, i.e., absorption of the axial and radial stresses which act on the casing string;
2) isolation of permeable formations, in order to prevent flow between different rock strata and, in particular, the contamination of the groundwater;
3) corrosion protection of the casing.
The cement is mixed with water to form a cement slurry, and a wide variety of additives are added to control the rheological properties, the setting time, the final strength, etc. The slurry is then injected with high pressure pumps through the borehole into the annulus between casing and formation.
Drilling continues in stages: they drill, then run and cement new casings, then drill again. When the rock cuttings reveal the oil sand from the reservoir rock, they may have reached the final depth. At this point, they remove the drilling apparatus from the hole and perform several tests to confirm this finding. These tests are:
Well logging – lowering electrical and gas sensors into the hole to take measurements of the rock formations there.
Drill-stem testing – lowering a device into the hole to measure the pressure, which will reveal whether reservoir has been reached.
Core samples – taking samples of rock to look for characteristics of reservoir rock.
By perforating the casing and cement sheath, the well is hydraulically connected with the reservoir, so that the production fluid can enter the well with the least possible pressure drop. Currently, shaped charges are exclusively used for perforation. They are introduced into the borehole on a self-supporting cable and ignited. The number of perforations, their arrangement, penetration, and size depend on the rock hardness and borehole conditions.
Then, tubing is run down the wellbore. The tubing string transports the fluid produced to the surface. The tubing is landed in the wellhead at the surface and anchored, if necessary, at the lower end. The annulus between casing and tubing can be sealed with a packer if the conditions in the well require it.
When the packer is set at the production level, it is expanded to form a seal around the outside of the tubing. Finally, they connect a multi-valved structure called a Christmas tree to the top of the tubing and cement it to the top of the casing. The Christmas tree allows them to control the flow of oil from the well.
Ex. 7. Decide whether the following statements are True or False, according to the text.
Well drilling is a relatively modern technology.
The application of high-speed rotary drilling has enabled engineers to drill deeper into frozen formations.
Rotary drilling is the most common drilling technique.
Despite its advantages, rotary drilling has a great risk of blowouts.
Before starting to drill, it is necessary to get the lease agreement for land.
It is always necessary to drill a water well to provide water for drilling.
The pit should have protective inside lining.
The cellar is the point where the drilling will start.
The rig is necessary to drill the first part of the hole.
The surface hole is as deep as the supposed oil trap.
The turntable is placed in the hole together with the drill bit.
The mud carries cuttings away from the hole.
The casing helps to strengthen the walls of the borehole.
It is necessary to test the cement seal immediately after running it outside the casing.
Drill stem testing analyses cuttings for hydrocarbon presence.
Perforating charges are ignited at the wellhead.
The packer is needed to isolate the annulus around the tubing.
The Christmas tree allows to regulate the fluid flow.
Ex. 8. Choose the correct variant.
The search for iron ore and coal / methane in the 19th century forced the development of deep drilling engineering.
At the beginning of the 20th century high-speed rotary percussion / compression drilling with circulating drilling mud began to be applied.
The rotary drilling method, developed in Russia / the United States at the end of the 19th century, with powerful roller cone / diamond chip drill bits is the most popular method of drilling.
Sale / Lease agreements for the land must be obtained and evaluated legally.
In drilling operations, there must be a source of sand / water nearby.
The reserve pit is used to dispose of rock cuttings / used water and drilling mud during the drilling process.
The derrick / cellar provides a work space around the hole, for the workers and drilling accessories.
Once they reach the pre-set depth, they must run and cement the casing / tubing.
The cement is allowed to harden and then tested for such properties as hardness / density, alignment and a proper seal.
Cementing of the casings allows to isolate porous / permeable formations, in order to prevent flow between different rock strata and, in particular, the contamination of the reservoir fluids / groundwater.
The drilling mud / cement is mixed with water to form a slurry, and a wide variety of additives are added.
Drill-stem testing involves lowering a device into the hole to measure the pressure / temperature, which will reveal whether reservoir has been reached.
Through perforation the well is hydraulically connected with the reservoir, so that the production fluid can enter the well with the maximum / least possible pressure drop.
The tubing string / drillstring transports the fluid produced to the surface.
The Christmas tree is a two- / multi-valve structure.
Ex. 9. Arrange the following operations in the correct order.
The kelly and the turntable are attached.
Christmas tree is attached at the wellhead.
A reserve pit is dug.
The drillpipe, the drill collar and drill bit are removed.
Access roads are built.
New sections of the drillpipe are added.
Tubing is run down the hole.
Drilling begins.
The pre-set depth is reached.
Lease agreements for the land are obtained.
The casing is run down and cemented.
The casing is perforated.
The drill bit, drill collar and drillpipe are placed in the hole.
Ex. 10. VOCABULARY. In the text above, find the equivalents to the following words and phrases. (The sequence corresponds to their occurrence in the text.)
глубокое бурение
насыщенный солевой раствор
исследовать, производить разведку
неглубокий, мелкий
рудные жилы
находиться в состоянии застоя
сырье
поташ
железная руда
способствовать, содействовать
ударно-вращательное бурение
циркулировать
буровой раствор
шахта
доминирующий
турбобурение
вязкопластичный
шарошечное коническое долото
выброс
многочисленный
проводить изыскания, съемку
экологическое воздействие
лицензионное соглашение
бригада
разравнивать
подъездные пути
выкапывать
амбар, отстойник
утилизировать
буровой шлам
выстилать
площадка, место
болото
дикая местность, заповедник
прямоугольный
устьевая шахта скважины
бурильные принадлежности
передвижной буровой станок
буровая установка
направляющая обсадная труба
временно
буровое долото
утяжеленная буровая труба
бурильная труба
квадрат, ведущая буровая труба
роторный стол
выносить (жидкостью)
секция
устанавливать (в глубину)
обсадная колонна
обрушиваться, обваливаться
ограничитель, регулировочная шайба
твердость
центровка
изоляция, герметичность
отводить, отклонять
нагрузка
поглощение
осевое напряжение
радиальное напряжение
загрязнение
грунтовые воды
коррозионная защита
цементный раствор
добавки, присадки
реологические свойства
время схватывания цемента
прочность
межтрубное пространство
нефтеносный песок
опробование скважины пластоиспытателем
перфорировать
цементное кольцо (в обсаженной колонне)
падение давления
кумулятивный заряд
воспламенять
НКТ (насосно-компрессорная колонна)
устье скважины
закреплять
пакер
клапан
фонтанная арматура
Ex. 11. From the Vocabulary List above, find antonyms to the following items.
develop
secondary
fire up
purification
mount
permanently
deep
discourage
Ex. 12. Match words from Column A to the words from Column B in order to form phrases. Translate the resulting phrases into Russian. Make up five sentences with these phrases.
Column A
|
Column B |
|
|
Ex. 13. The Vocabulary List contains a number of useful terms. Match the terms and their explanations.
a) turbodrill |
g) blowout |
b) cellar |
h) spacer |
c) rotary percussion drilling |
i) rheological properties |
d) drill-stem testing |
j) conductor pipe |
e) kelly |
k) oil sand |
f) wellhead |
l) packer |
__________ is an expanding plug used in a well to seal off certain sections of the tubing or casing when cementing.
The __________ is a heavy square steel pipe suspended from the swivel through the rotary table to turn the drill stem as the rotary table turns.
__________ indicate flow characteristics of a fluid and most often refers to plastic fluid parameters and PV plastic viscosity.
A __________, which is also rectangular in shape, is dug around the location of the real drill hole. The cellar is actually a place of work for the workers as well as is made for housing the drills and accessories.
A __________ is used to close off the annular space between tubing or drill pipe and casing and to provide a constant annular space around the casing.
__________ is a relatively loose sandstone, or porous carbonate rock, impregnated with bitumen
In __________, the drill bit spins much faster than on a conventional motor drill, which results in the increased speed and straighter holes.
A __________ is a procedure for testing the surrounding geological formation through the drill pipe.
Failure of well control systems can lead to a heavy __________.
__________ is run because the shallow section of most wells onshore is drilled in unconsolidated sediment and the direction of drilling needs to be secured.
__________ is typically cemented in place during drilling operations and forms an integral structure of the well.
In __________ a heavy metal bit attached to a cable is alternately raised and dropped, pulverizing the rock beneath it, while constantly rotating.
Ex. 14. Insert appropriate items from the box into the following sentences. Sometimes you will have to change the form of the word.
a) raw material |
e) turntable |
i) additives |
m) cement sheath |
b) viscoplastic |
f) joint |
j) setting time |
n) tubing |
c) access roads |
g) collapse |
k) drill-stem testing |
o) valve |
d) drill bit |
h) seal |
l) perforate |
p) Christmas tree |
In case of a blowout the crew can shut a safety __________ at the Christmas tree.
Cement __________ is affected by a number of items including: cement fineness, water-cement ratio, chemical content (especially gypsum content) and admixtures.
Flexible cement systems can be designed and installed so that the__________ can withstand the expected stresses in the well.
Examples of __________ fluids are drilling mud, mayonnaise, toothpaste, and blood.
The standard length of the __________ of drill pipe or tubing is 9 m.
Typically, casing is __________ to establish fluid communication between the formation and wellbore for production of the hydrocarbons.
The typical __________ will be split into four periods: pre-flow, initial shut-in period, a main flow period and a final shut-in period.
The search for __________ at the age of industrialization encouraged the development of drilling technologies.
The cement slurry is carefully designed with functional __________, such as accelerators or extenders.
Soft formation __________ are used in unconsolidated sands, clays, soft limestone, and shale.
A __________ often provides numerous additional functions including chemical injection points, well intervention means, pressure relief means and well monitoring points.
The space occupied by an __________ should be computed as 60 feet wide for the distance of the actual route to the drillsite.
The first thing to start rotary drilling is to run the kelly through the __________ and thread the pilot bit to the kelly.
The cement casing __________ is an impervious barrier placed between the well casing and the formation.
A __________ is a small-diameter pipe that is run into a well to serve as a conduit for the passage of oil and gas to the surface.
To prevent the casing from __________, it must be cemented in place.
Ex. 15. Translate the following sentences into English, using vocabulary from the text and terms given at the beginning of the Unit. (The items are underlined.)
В древние времена бурение неглубоких скважин осуществлялось вручную.
При ударно-вращательном бурении мощность передается от двигателей роторному столу, установленному на устье скважины.
Ведущая буровая труба удерживает вес бурильной колонны при глубоком бурении.
Шарошечные конические долота разной конструкции являются самым распространенным бурильным инструментом.
Буровой раствор охлаждает долото на забое скважины и выносит обломки породы на поверхность.
Цементный раствор укрепляет стенки скважины и предотвращает ее обвал.
Наружный диаметр кондуктора немного меньше диаметра направляющей трубы.
Турбобуры предназначены для бурения вертикальных и наклонно-направленных нефтяных и газовых скважин с использованием бурового раствора высокой плотности.
Цементное кольцо обеспечивает коррозионную защиту обсадных труб.
Перфорация с использованием кумулятивных зарядов применима в большинстве твердых видов пород.
Лицензионное соглашение на этот участок еще не получено, поэтому мы пока не имеем права строить подъездные пути.
При бурении скважины глубиной 2600 м в амбаре содержится около 65% воды, 30% шлама и 5 % нефти.
Фонтанная арматура регулирует поток флюида и осуществляет контроль давления в затрубном пространстве.
Для бурения первоначального неглубокого отверстия бурильщики используют передвижной бурильный станок, а потом уже бурят с помощью буровой установки.
Обсадная колонна выполняет функцию защиты для насосно-компрессорной колонны и другого оборудования, используемого в скважине.
Некачественное выполнение цементирования ухудшает реологическое свойства цементного раствора и нарушает центровку обсадной колонны.
Для установки и закрепления пакера подбирают интервал, представленный монолитными малопроницаемыми устойчивыми породами.
Эти добавки позволяют регулировать скорость схватывания цемента.
В настоящее время доступны различные системы для проведения опробования скважины пластоиспытателем, позволяющих существенно сократить сроки испытания.
Чем глубже бурение, тем больше высота и грузоподъемность вышек.
Ex. 16. Look at the diagram of the rotary drilling process and find the pieces of equipment indicated. The Russian translation is given.
A |
Drill pipe |
|
B |
Drilling hook |
|
C |
Rotary swivel |
|
D |
Flexible hose |
|
E |
Rotary table |
|
F |
Preventer |
|
G |
Vibrating screen (shaker) |
|
H |
Pit |
|
I |
Cement sheath |
|
J |
Casing |
|
K |
Hollow drill pipe |
|
L |
Circulating drilling mud |
|
M |
Drill collar |
|
N |
Roller cone bit |
|
O |
Rock strata |
|
P |
Reservoir rock horizon |
|
Ex. 17. From the list of pieces of equipment above, find the terms for the following definitions.
The main component of the rotating machine which turns the drill string.
A series of trays with vibrating screens which allow the mud to pass through but retain the cuttings.
The large component attached to the travelling block from which the drill stem is suspended via the swivel.
A component which is suspended from the hook. It allows mud to flow from the rotary hose through the swivel to the Kelly.
A heavy, thick-walled steel tube which provides weight on the bit to achieve penetration.
A heavy seamless pipe which is used to rotate the bit and circulate the drilling fluid.
Ex. 18. Speak about the functions of the following pieces of equipment. Use expressions from the text and the definitions at the beginning of the Unit.
Drill pipe
Flexible hose
Rotary table
Preventer
Vibrating screen
Pit
Cement sheath
Casing
Drilling mud
Drill collar
Roller cone bit
Ex. 19. Analyze the following pictures of various kinds of drill bits. Discuss why they have a particular shape. Use the following expressions:
coarse teeth – крупные зубцы
fine teeth – мелкие зубцы
conically shaped – конический
