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possibility of their usage for measuring high pressures at very high
о
temperatures (up to + 400 С).
There are a lot of downhole pressure gages. But the most simple
and commonly used is the downhole helix pressure gage DPGNS-2

(МГН-2) with the self-contained recording (fig. 11.1). It is named as
downhole pressure gage of the normal series. It is applied for
measurement of pressures in producing wells.

Helix downhole pressure gage DPGNS-2 (МГН-2) consists of

body 7, clockwork drive 1, helix 8, bellows 9, body of bellows 10,
reduction gear 2, lead screw 3, carriage (glass) 4, pen 5 and sleeve 6.
The multicoil hollow tube spring (helix) is the sensitive element

in this downhole pressure gage. Helix is filled with light oil under the
vacuum. The drawing pen is attached to the free end of the helix.

This pen draws the line on the diagram blank at the turn of the

helix. The principle of helix downhole pressure gage DPGNS-2
(МГН-2) operation consists in following: after putting the downhole
pressure gage down to the necessary depth the well pressure p through

the holes in the body of bellows 10 affects bellows 9. The bellows
and helix 8 are linked (they are the linked vessels). The bellows the
same as the helix are filled with light oil. The bellows work as liquids

separator. They contact with the well fluid and so the pressure of the
well fluid is transmitted through the bellows without losses to
the liquid inside of the helix. Under this pressure influence the free
end of the helix with drawing pen 5 is turned to the angle proportional

to the measured pressure. The pen draws the line on the blank inserted
into the carriage (glass) 4. To get the continuous measurement of
pressure change at time the carriage (glass) moves onwlardly on the

lead screw 3 which is rotated by the clockwork drive 1.
All parts of downhole pressure gage DPGNS-2 (МГН-2) except
bellows are located in the hermetical body. The atmospheric pressure
is kept inside of this body. The bellows are located in the separate

body. As a rule there is an ordinary maximum thermometer in the
special chamber in the lower part of the device. The maximum
thermometer is used for recording the bottom hole temperature and

putting the temperature corrections to the readings of the downhole
pressure gage.
The diagram blank of the special paper or metallic foil with

coating is inserted into the internal side of the carriage (glass). The

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