Borehole Engineering Services

The success of the water well drilling operations increasingly led to clients asking Drilcorp to provide additional services related to water wells eventually prompting management to create a new division of the company dedicated to non-drilling services. Borehole Engineering Services division was established. This division of the Company has fully trained engineers dedicated to specialist testing, monitoring, surveying, borehole referbishment  and remediation and decommissioning of boreholes. The division is also a distributor for borehole equipment and pump manufacturers.

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Case Study

Drilcorp’s Borestorer advanced borehole jetting technology, completes chalk aquifer borehole refurbishment.

Challenge

A major UK water supply company approached Drilcorp’s Borehole Engineering Services division (BES) to rehabilitate two of their supply boreholes in the Chalk Aquifer, where elevated turbidity in raw water was causing issues and knocking off the supply. The main objectives of the project were for BES to: (i) assess the extent of the issue at hand and the source of turbidity; (ii) remove iron-oxide slime using their flagship borehole jetting system the Borestorer; (iii) airlift/remove debris and sediment build up at the base of the boreholes; and (iv) disinfect the borehole. Any water produced during the project had to be treated to stringent water quality standards before it could be discharged into a river nearby.

Solution

BES carried out the following sequence of operations at the boreholes:

1.Removal and inspection of the permanent pumping equipment;
2.Pre-clean downhole camera inspection;
3.Geophysical logging;
4.Borehole jetting with the Borestorer;
5.Backfilling (one borehole only)
6.Airlift pumping;
7.Borehole treatment with chlorine dioxide;
8.Airlift pumping;
9.Post-clean downhole camera inspection;
10.Cleaning, inspection and reinstallation of the permanent pumping equipment;
11.Clearance pumping.

The airlifted water was de-silted in a series of settlement tanks and any free chlorine was neutralized with sodium thiosulphate.

Results

The sequence of operations delivered outstanding results:

-Removal of large quantities of iron-oxide slime/encrustations on the casing and borehole wall;
-Identification of a well-connected fracture network in the aquifer, discovered during chemical dosing of the boreholes by analysing free chlorine concentrations
-Rejuvenation of the mild steel casing;
-Initial results suggest an improvement on their longstanding turbidity issue;

No environmental impact on the nearby stream.

Drilcorps’ Borestorer jetting unit
Drilcorps’ Borestorer jetting unit
Before jetting: chalk borehole wall covered by iron-oxide slime
Before jetting: chalk borehole wall covered by iron-oxide slime
After jetting: large quantities of iron-oxide slime removed, as was the case throughout both boreholes
After jetting: large quantities of iron-oxide slime removed, as was the case throughout both boreholes

Borestorer®

Aquifer Testing & Monitoring

Borehole Refurbishment & Remediation

Surveys CCTV & Deviation (Verticality)

Decommissioning

Maintenance & Continuity plans

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