Unit 13 drilling problems. Stuck pipe.

13.1. Remember the meaning of the following words and word-combinations:

hostile environment – (зд.) в трудных климатических условиях

stuck pipe – прихват трубы

pressure differential – перепад давления

prevention measures – меры предотвращения

friction reducing component – понизитель трения (для бурового раствора)

spiral drill collar – спиральная УБТ (утяжеленная бурильная колонна)

absorb – поглощать

swell – набухать, раздуваться

potassium salt – соли калия

badly worn drill bit – очень изношенное буровое долото

undergauged hole–ствол скважины с диаметром меньше номинального

string reamer – расширитель колонны

drilling assembly – буровой снаряд (бурильная колонна со скважинным

буровым оборудованием и инструментом)

residual stress – остаточное напряжение

high mud weight – высокая масса бурового раствора

dogleg – резкое искривление ствола скважины

groove – выемка, желобок (в стенке скважины)

key seating – образование желобов на стенках скважины

avoidance – (зд.) устранение

reaming – расширение ствола скважины

key seat wiper = string reamer – расширитель для сглаживания резких

перегибов ствола и жёлобов

retrieve – извлекать (инструмент из скважины)

explosive – взрывчатое вещество, заряд

chemical charge – химический заряд

sever – разъединять

sidetrack – забуривание нового ствола из скважины

retrieve the tubular – извлечь \ достать трубу

13.2. Read and translate the text using a dictionary:

DRILLING PROBLEMS. STUCK PIPE.

Drilling equipment and drilling activities have to be carried out in complex and often hostile environments. Surface and subsurface conditions may force the drilling rig and crew to operate close to their limits. Sometimes non-routine or unexpected operating conditions will exceed the rating of equipment and normal drilling practices may not be adequate for a given situation. Thus, drilling problems can and do occur.

Stuck Pipe

This term describes a situation whereby the drill string cannot be moved up or down or rotated. The pipe can become stuck as a result of mechanical problems during the drilling process itself or because of the physical and chemical parameters of the formation being drilled. Most common reasons for stuck pipe are:

• Excessive pressure differentials between the borehole and the formation. For
instance, if the pressure of the mud column is much higher than the formation
pressure the drill pipe may become ‘stucked’ against the borehole wall. This often happens when the pipe is stationary for some time. Prevention methods include: reduced mud weights, adding of friction reducing components to the mud, continuous rotation / moving of string, adding of centralizers or use of spiral drill collars to minimize contact area between string and formation.

• Some clay minerals may absorb some of the water contained in the drilling mud.
This will cause the clays to swell and eventually reduce the borehole size to the
point where the drill pipe becomes stuck. Prevention: mud additives which prevent
clay swelling e.g. potassium salt.

• Unstable formations or a badly worn drill bit may result in undergauged holes. An
example for unstable formations is salt which can ‘flow’ while the drilling is in
progress, closing around the drill pipe. Prevention: adding of stabilisers and string
reamers to the drilling assembly.

• Residual stresses in the formation, resulting from regional tectonic forces may
cause the borehole to collapse or deform resulting in stuck pipe. Prevention:
sometimes high mud weights may help delay deformation of the borehole.

• If the well trajectory shows a severe dogleg (sudden change in angle or direction)
the movement of the string may result in a groove cut into the borehole wall by the
drill pipe. Eventually the pipe will become stuck, a process termed key seating
(Fig. 18). Prevention: avoidance of doglegs and frequent reaming, insertion of
stabilizers on top of drill collars, insertion of key seat wipers in the string (‘string
reamers’).

Figure 18. Development of key seating (plan view of hole).

In many cases the point at which the pipe is stuck can be determined by means of a ‘free point indicator tool’, a special electrical strain gauge device run on wireline inside the drill pipe which will measure axial and angular deformation.

If the string indeed cannot be retrieved, an explosive or chemical charge is lowered inside the pipe to the top of the stuck interval and the pipe above the stuck point is recovered after severing the string. Since drilling assemblies and redrilling of the borehole in a sidetrack are expensive, a further attempt to retrieve the tubulars (often called a ‘fish’) left in the hole will then be made.

13.3. Give English equivalents of thefollowing expressions. Use the text:

Работать на грани возможности; превышать возможности оборудования; проблемы с бурением могут возникнуть и возникают; колонна не может двигаться вверх, вниз или вращаться; когда труба остается неподвижной некоторое время; это вызовет разбухание глины; приводя к прихвату трубы; замедлить деформацию скважины; резкое изменение угла или направления; в конце концов труба застрянет; индикатор глубины прихвата колонны; спускаемый на вспомогательном канате; измерять осевую и угловую деформацию; опускается в трубу; так как забуривание нового ствола из скважины дорогостоящий процесс.

13.4. Match the words in column A with their equivalents in column B:

A B

1) stage 2) various 3) liquid a) discover b) produce c) part

4) recover 5) above 6) call d) fluid e) step f) grow

7) increase 8) restrict 9) proportion g) different h) over i) limit

10) normal 11) matter 12) boundary j) common k) under l) name

13) find 14) below 15) enormous m) substance n) border o) huge

13.5. Complete the sentences in column A choosing the correct ending from

column B:

A B

1) The situation when the drill string a) … means of a ‘free point indicator

cannot be moved up or down or tool’.

rotated ………

2) Clay minerals may absorb some of b) ……. expensive.

the water and swell …………..

3) Unstable formations or a worn bit c) …. an explosive or chemical charge is

may result in …………… lowered inside the pipe.

4) The point at which the pipe is stuck d) …. stuck pipe.

can be determined by ………….

5) If the string cannot be retrieved by e) …. undergauged holes.

overpull, ………

6) Redrilling of the borehole in a f) …. and reduce the borehole size.

sidetrack is …………

13.6. Answer the following questions on the text:

1) Why do drilling problems occur? 2) What does the term ‘stuck pipe’ mean?

3) What are most common reasons for stuck pipe? 4) When do excessive pressure differentials between the borehole and the formation often happen? 5) What are the prevention methods for this problem? 6) What problem can clay minerals cause? 7) What is the prevention in this case? 8) What may unstable formations like salt result in? What should be done? 9) What may residual stresses cause? 10) What may help delay deformation of the borehole? 11) How is a sudden change in angle and direction called? 12) How to avoid key seating? 13) What is a ‘free point indicator tool’ and what is it used for?

13.7. Translate in writing abstracts describing two of the most common reasons for stuck pipe.

13.8. Make up sentences using the following words:

a.may formation ‘stuck’ the borehole The drill pipe of excessive because pressure against differentials wall between become the borehole and the.

b. electrical cases a stuck special strain In pipe many gauge device the point at determines which the is.

13.9. Render the text “Drilling problems. Stuck pipe” in Russian or in English.