GONFLAGE ET DEGONFLAGE DE L'OBTURATEUR

Different parameters determine the use of inflatable packers.

These must be clearly identified in order to define the most suitable procedure for the planned application in each case.

One of these parameters is the diameter of the bore-hole: the greater the diameter of the bore-hole, the smaller the maximum operating pressure for the same packer.

Another parameter is the depth of use and the water level in the bore-hole.

As well as this, it is advisable to check the static water level (SWL) before and after placing the packer into the bore-hole.

The choice of inflating fluid (water or gas) depends mainly on the difference between the depth of use and the hydrostatic level in the bore-hole (SWL).

1) when inflating with gas, the pressure applied from the surface (pressure gauge) must correspond to the desired inflation pressure, to which shall be added the pressure from the water-column ( one bar per 10 metres of water-column) on the packer.

For example, an packer is placed 100 m below the water level (SWL) and must be effectively inflated to 20 bar. In this case, gauge pressure must be 30 bar: 100 metres of water-column is approximately 10 bar plus the 20 bar of pressure for inflating the packer.

2) Water inflation. In this case, the pressure to be applied from the surface (pressure gauge) must correspond to the desired inflation pressure, which will be decreased by the pressure from the height of the water (A) contained in the inflation hose between the surface and the static water level (SWL).

Using the same example for a height A of 5O metres, the pressure read on the surface pressure gauge must be 15 bar, i.e. 20 bar less 5 bar (50 metres).

Water inflation also has several other advantages such as its low cost, availability and ease of transport.

N.B.Sometimes the pressure resulting from the height of the water A in the inflation hose is sufficiently high to make it impossible to deflate the packer (see expansion curves). Geopro has a deflation device which makes it possible to use water as the inflation fluid in most applications.