Early hydraulic borehole tests as well as borehole completion operations
at the HDR geothermal test site at Soultz-sous-Fôrets were characterized
by several technical problems due to conventional (rubber-based) packer
technology at temperatures exceeding 120 to 140 °C, and high gas- and
salt content of the borehole fluids. After extensive investigations with
aluminum, copper, and even stainless steel as packer material for different
applications such as hydraulic / hydrofrac testing at great depth or
permanent borehole sealing for nuclear waste storage, casing packers consisting
of soft metal shells of salt water resistant copper - nickel alloy
mounted on a mandrill of 7" or 9-⅝" casing were developed during the
past years to overcome these problems.
After numerous laboratory prototype tests, the new casing packer
technology was successfully used during the extension of borehole GPK-2
and the completion of the boreholes GPK-3 and GPK-4.