Revised Standard from Last Update.

1. SCOPE

1.1 The standard lays down the requirements for material for use as filter pack material in tubewells as source of water. In filter packed wells the zone immediately around the screen is made more permeable by packing it with specially graded material-filter pack earlier known as gravel pack.

1.2 In filter packed wells, the zone immediately around the well screen is made more permeable by removing some formation material and replacing it with specially graded material. This relatively thin zone separates the screen from the formation material and increases the effective hydraulic diameter of the well. A filter pack is advantageous when the small slot size dictated by natural development limits the transmitting capacity of the screen so that the desired yield cannot be obtained. Use of certain drilling methods such as reverse rotary, the borehole diameter cannot be less than 400 mm which is much more than required for installation of the screen and hence filter pack is required to be placed in the annular space. In fine grained uniform sand, friable sand stone, extensively laminated formation (thin layers of fine, medium and coarse sediments), a filter pack is always recommended to get sand free yields.

2. REFERENCES

The standards listed below contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards listed below:

1811 : 1984 Methods of sampling foundry sands (first revision)