STRAIGHT HOLE DRILLING

Frequently it is necessary to drill a straighter hole than was originally planned when the job was started with a certain string of drill collars. Also, it may happen that it is desired to put more weight on the bit without increasing the deviation. The best single proven way to do either of these things with the same string of drill collars is to add stabilizers. For deviation control a single stabilizer is sufficient if it is properly located in the drill string. The proper location is the first bend in the drill string above the bit. Since the bending point depends on the hole size, drill size and weight on the bit, it may occur at different points. To some extent the placement is also dependable on the formation characteristics.

It has been considered good practice in some cases to space additional stabilizers about one stand apart through a portion or all of the rest of the drill collar string. The additional stabilizers do not help to keep the hole straight. They do help in preventing wall sticking and other problems associated with hole conditions.

With the use of stabilizers, it is important to remember that stabilizers are usually the weakest point in the drill string and, therefore, subject not only to wear but failure. Some of the more modern stabilizers have been designed so that the wings do not create a serious hazard in the hole. For example, some of these are made of drillable material and some may be removed with washover pipe.

By reducing the weight on the bit, the bending characteristics of the drill string are changed and the hole will tend to be straighter. One of the oldest techniques for straightening a hole was to reduce the weight on the bit and speed up the rotary table. In recent years it has been found that this is not always the best procedure because reducing the bit weight sacrifices considerable penetration rate.

The straightening of a hole by reducing bit weight should be done very gradually so that the hole will tend to return to vertical without sharp bends and will therefore be much more safer for future drilling.

The words to be memorized:

1. Bending point – точка перегиба

2. Penetration rate – скорость проникновения

3. Space – помещать, размещать

4. Washover pipe – промывочная труба

5. Stabilizer – стабилизатор

6. Sticking – прихват

7. Collar – муфта трубы

8. Drilling equipment – буровое оборудование

9. Rotary table – роторный стол

10. Bottom-holeassembly(ВНА) – компоновка инструмента для бурения

11. Logging – каротаж

12. Blowout preventer (ВОР) – противовыбросовый превентор

13. Pay zone – продуктивная зона

14. Wild well –неуправляемая скважина;

15. Kill line –линия глушения;

16. Flare pit –факельный амбар;

17. Dummytrip – «холостой» подъем-спуск