Unit 8 Blowing-out the well

Ex.1 Read and translate international words.

Circulation, agent, column, effect, liquid, technique, engine, internal, fluid, principle, operation, particle, risk, produce, process, rock, purification, hydrostatic, condition, absorption, compressor, conduct, pulp, limited, geophysical, control, phenomenon, emission.

Ex.2 Learn the new words.

rate of penetration - механическая скорость проходки	integrity - сохранность
footage per bit - проходка на долото	to affect adversely –отрицательно влиять
gumbo – вязкая порода	strata pressure – пластовое давление
blowing the well – продувка скважины	drill cutting - буровой шлам; обломки выбуренной породы
gaseous agent – газообразный агент	exhaust - выхлопной
pipe string – колонна труб	to descend - погружать(ся)
annulus – затрубное пространство	liquid column – столб жидкости
bit cooling – охлаждение долота	circulation - циркуляция
arid zone – засушливая зона	to adhere – плотно прилегать, налипать
landslide - обвал	water seepage – просачивание воды
fractured - трещинный	advanced techniques - новейшие методы
tricky rocks – каверзные породы	internal combustion engine – двигатель внутреннего сгорания
to percolate - просачиваться, проникать

Ex.3 Read and translate the text.

Blowing out the well

The essence of the blowing wells lies in the fact that all procedures like cleaning the wellhead, removal of drill cuttings to the surface, cooling the bit are fulfilled with the help of gaseous agents instead of drilling fluid. These agents are: compressed air, natural gas and exhaust fumes of internal combustion engines.

To blow the well pipe string is descended to the bottom of the borehole, but, instead of water, air is supplied under pressure of 10-15 atm. The principle of operation is the following: through annulus dirty water and rock particles are emitted from the bottomhole to the surface.

Process of blowing well with air or gas has several advantages over that with drilling fluid:

1) increasing the rate of penetration (ROP) ¹ and footage per bit² due to better purification of the borehole from cuttings, the lack of hydrostatic pressure in liquid column and advanced techniques of bit cooling;

2) improving conditions for drilling wells in fractured and tricky rocks, where the wells can be absorbed by the washing fluid; this phenomenon causes partial or complete loss of circulation;

3) facilitating conditions for drilling wells in arid zones;

4) providing better integrity of productive stratum;

However, blowing is not always conducted. Problems arise while drilling in aquifers where significant water losses take place. The increase of hydrostatic pressure in liquid column affects adversely the work of compressors. It is also difficult to drill gumbo (clay type) which adheres to the walls of the borehole and forms seals on drill string.

The main disadvantages of drilling well with air or gas are:

a) water seepage while drilling gumbo and soft rock, because the pulp produced does not allow blowing out the well;

b) danger of landslide;

c) inability to control strata pressure;

d) risk of fires and explosions;

e) limited area for geophysical work.