2. Pay attention to the pronunciation of the following words:

• success

• signs of outer bearing failure

• sulfur compounds

• undue stress

• undergauge hole

• reaming

• deleted gauge row teeth

• severe cone erosion

• uncirculated junk

3. Read and translate the text

When a decrease in penetration rates calls for a change in the bit, it is necessary to trip out, giving the driller or toolpusher a chance to examine the used bit. Even a bit well-suited for the formation in which it is drilling will show some wear, and how it wears is valuable information. An experienced toolpusher, by reading the dull bit appearance, can see firsthand the relative success or failure of the drilling program he is following.

Skid marks on cones or a locked cone are signs of outer bearing failure. This problem is usually caused by excessive weight and rotary speed, but it can also result from sulfur compounds or abrasive materials in the drilling fluid. Inner bearing failure is usually the result of an improper bit selection. A bit designed for harder formations, run with a reduced rotary speed, will present undue stress on the bearings.

Extreme wear on the gauge teeth of the bit can result from improper bit type, unstable drill collars, or excessive rotary speed. Changing to a bit that is more suitable for harder formations and with greater gauge pro­tection can help remedy this situation. Exces­sive gauge wear can be critical because a hole that is drilled undergauge just creates new costs in reaming or in damage to the drill stem. An undergauge hole, the result of the bit wearing to a diameter less than, full gauge, is cone-shaped, and it must be reamed to full gauge by the next bit.

Tooth breakage results from the use of a bit that is not suited for varied or unconsolidated formations. As the drill string breaks through from one rock type to another, it may bounce, and the bit teeth must be able to with­stand the shock load. Short-tooth bits, less bit weight, and reduced rotary speed should be em­ployed. Also, a clean hole must be maintained to avoid excessive junk, which can cause tooth breakage.

When the inner rows of bit teeth wear faster than the gauge teeth, improper bit selection can be suspected. A bit with deleted gauge row teeth or a hard-formation bit may be necessary.

In using insert bits, broken inserts are the most common problem, and they, too, can usu­ally be traced to bit selection. The longer inserts characteristic of soft-formation bits cannot withstand the shock loads encountered in hard formations. Unnecessary wear to the outside rows of hard-formation bits is evidence that excessive rotary speed is being employed.

Improper drilling practices are also evident in wear on bit cones. Severe cone erosion sometimes resulting in a cracked cone is usu­ally caused by a combination of excessive drill­ing fluid flow and uncirculated junk in the hole. Off-center wear can be remedied by measures to increase the rate of penetration. Center coring, the wearing away of a cone's nose area, can cause insert loss or cone breakage. Just as there is a code for classifying bits by design and expected performance, dull bit condi­tion can also be recorded using another IADC system. This code uses combinations of letters and numbers to indicate the type and degree of wear to bit cutting structures, bearings, and cones. This information, when entered on the bit record, serves as a useful check on bit selection and drilling practice and helps keep drilling costs down.

4. Give the adequate Russian variants for the following word combinations:

The dull bit appearance; to see firsthand; inner/outer bearing failure; undue stress; exces­sive gauge wear; to be drilled undergauge; to remedy situation; a bit with deleted gauge row teeth;

a cone's nose area; a code for classifying bits by design and expected performance.

5. Find in the texts the English equivalents for the following words and word combinations and learn them by heart:

Поднять инструмент из скважины; засоренная шарошка; утяжеленная буровая труба; бурить скважину меньшего диаметра; обрабатывать ствол скважины расширителем до полного диаметра; резкое сотрясение бурильной колонны; внешние зубья; сокращать затраты на бурение.

6. Analyze the information regarding bit wear and complete the chart:

problem	reasons	remedy

7. Explain how the dull bit appearance can indicate success or failure of the drilling program.

8. Make up the dialogue between an experienced toolpusher and a beginner. Imagine that you have got some problems with bit wear (tooth breakage; bearing failure; etc.). Discuss possible reasons of it. Suggest the solution of the problem.