Read and translate the text. One important consideration when starting a job is the derrick or mast to be used

One important consideration when starting a job is the derrick or mast to be used. A derrick or mast is the steel structure that supports many feet of drill pipe, often weighing more than 100 tons.

A standard derrick is a structure with four supporting legs resting on a square base. It can be assembled piece by piece each time a well is drilled. In contrast, the mast is assembled once when it is manufactured. After manufacture, it remains a single unit and is raised and lowered as a single unit each time a well is drilled. When a mast is raised and lowered, it looks something like the blade of a huge jackknife being opened and closed. As a result, masts are sometimes referred to as jack-knife masts. The standard derrick-except as found on a few land rigs and many offshore drilling rigs-has become fairly rare today, the mast having all but replaced it.

The mast or derrick is erected on a substructure, which serves two main purposes: (1) to support the rig floor, providing space for equipment and workers, and (2) to provide space under the floor for special, large valves called blowout preventers.

The substructure supports not only the rotary table, but also the full load of the drill stem when the stem is suspended in the hole by the slips. It also supports a string of casing when the casing is being run in the hole by an arrangement of slips resting on the rotary or when it is being temporarily stored on the substructure. The rig floor also holds the drawworks, the driller's control panel, the doghouse, and other related equipment.

Derricks and masts are rated according to the vertical load they can carry and the wind velocity they can withstand from the side. Derrick load-bearing, capacity figures may vary from 250,000 to 1,500,000 pounds. A typical mast or derrick can withstand winds of about 100 to 130 miles per hour with the racks full of pipe and without the need for external guy wires attached to ground anchors.

Another consideration in the design of the mast is height. The derrick or mast and its substructure support the weight of the drill stem at all times, whether the stem is suspended on the crown block or resting in the rotary table. The height of a derrick or mast does not affect its load-bearing capacity, but the length of the sections of drill stem to be removed from the hole is limited by the height of the derrick or mast. This is because the crown block must be-sufficiently elevated above the derrick floor to permit the withdrawal and temporary storage of the drill stem when it is pulled from the well to change bits or for other reasons.

Drill pipe is pulled and racked in stands. A stand usually consists of three joints of pipe, each about 30 feet long. When a stand consists of three joints of pipe, it is sometimes called a thribble. Such a stand, having a total length of some 90 feet, can be accommodated in a derrick or mast that is 136 feet high.

3. Answer the following questions:

1. What is a derrick or mast?

2. What does derrick or mast support?

3. What is its weight?

4. What is the difference in structure between derrick and mast?

5. Does mast replace the derrick?

6. What are two main purposes that derrick serves?

7. What does the substructure support?

8. What additional pipes does the substructure support?

9. What equipment does the rig floor hold?

10. What wind velocity can a typical mast or derrick withstand?

11. Does the height of derrick or mast affect its load-bearing capacity?

12. Why is the length of the sections of drill stem limited by the height of the derrick or mast?

13. How is a drill pipe usually pulled and racked?

14. What is the length of each stem?

15. What is another name for a drill pipe usually pulled on stems of three joints?

4. Find the English equivalents for these words and word combinations in the text:

ü весить больше чем

ü фундаментная рама буровой мачты

ü собирать по частям

ü остаётся единой конструкцией

ü поднимать и опускать мачту

ü морская буровая установка

ü противовыбросовое оборудование

ü приостанавливается из-за скольжения

ü временно находиться

ü канаты, тросы

ü скорость ветра

ü несущая мощность

ü кронблок должен быть достаточно поднят

ü соединение из трёх труб

ü колонна обсадных труб

ü длина секций буровой колонны

ü сменить долото

ü изъятие и временное нахождение

Дата добавления: 2015-10-24