English to Russian Tech/Engineering Mining & Minerals / Gems бурение

Gravel Pack
• In each well, a gravel filter pack should be added, extending from the bottom of the well to
approximately 3m above the top of the slotted interval for exploration (Phase 1) wells and
10m for abstraction (Phase 2) wells.
• The gravel shall comprise clean, well sorted, well rounded and graded quartz grains with
the smallest grain size being larger than the casing slots / perforations (nominally 1-3mm
diameter). Filter pack materials should be inert, free from contaminations and very low in
calcareous content. Each tender submission will need to identify where this material will
be obtained from and if successful, pictures and samples may be requested in advance of
drilling.
• The filter pack will be installed directly into the annulus in a controlled manner using a
(tremie) pipe to prevent bridging. The filter pack should then be partially developed and
the pack topped up to account for any settlement that may have occurred. The tenderer
should detail the approach they will use for this.
Sand filter pack (Sand Break)
• Aim coarse (2 - 5mm) sand layer should be placed above the gravel filter pack. The
sand should be well graded, inert, contaminant free and very low in calcareous content.
• A 2m layer of bentonite in the form of pellets will be installed above the sand layer by
using a tremie pipe.
• Water may need to be added to the bentonite to promote the swelling if instructed by the
onsite hydrogeologist.
Backfilling
• Drill cuttings may be used to backfill the annular space above the bentonite seal as these
will likely be high in clay content.