Construction Of Deep Wells
Prior to drilling LDW will inspect the site and planning the followings.
1. Possible way of mobilizing machines
2. Planning the drilling method as per recommendation of hydro-geologist
3. Organizing the materials for drilling.
4. Organizing the suitable drilling rig to perform the job.
5. Organizing the working staff, their food, accommodation and transport
MOBILIZING THE MACHINES
A suitable drilling rig will mobilize to the site under the instruction and supervisor or drilling manager.
PERFORMING THE DRILLING
A drilling location will re-confirmed from the geologist as per his report. Most of the time checking the coordinates given by geologist and if any verifications required confirming over the phone or with GPS coordinates and parking the rig to the drilling point. Once the rig is parked to the precise point the rig will take on to the level jacks by levelling vertically and horizontally and make the machine ready for drilling.
There after preparing the bentonite mud pits, mud water circulation system and mixing bentonite solution to the fresh water till the solution velocity is capable to lift the drilling soil and performing drilling. (If required during the drilling the soil samples are collecting at every 3 meters intervals and any special hard or soft formation discovered immediate sample will keep for reference).
When drilled up to required depth as per hydro- geologists recommended depth, the drilling manager or supervisor (or the well design given in the survey report can be followed) will discuss with geologist about the details of the strata to decide the casing of well. After discussion we decide the depth of screened and blank casing to be installed.
After inserting the casings in the hole, the filter media will be inserted gradually with water to the space between the casing and soil bank up to a thickness of 3 inch. Normally the blank hole to be the size of 1.5 times of the casing diameter. Once the filter media is inserted the rig will do the surging and bailing process to pack the filters sand around the entire well casing. This process will make sure there is no cavities or air pockets between the casing and wall.
Then the rig will start flushing the well with fresh water sweeps through the screens to the well by compressed air. While flushing the driller will check the turbidity of the water and if necessary will repeat the bailing and surging process for further packing of filter sand and if necessary will add the filter sand to maintain the required height of the pack.