Method for insulating and lining a borehole in permafrost

Claim 1

A method for insulating and lining a borehole penetrating a subterranean region comprising forming a liner in situ by hardening in place a hardenable, flowable composition consisting essentially of a hardenable, flowable, adhesive cement and a divided, solid, closed-cell material, wherein the divided, solid, closed-cell material comprises as much as about 80 volume percent of the hardenable, flowable composition, and wherein the hardened material forming the liner has a hydrostatic crush strength of at least about 200 psi; wherein the hardenable, flowable composition contains about 10 to 60 volume percent of hollow siliceous microspheres whose diameters are in the range of 1 to 1000 microns having wall thicknesses of 0.5 to 10 percent of their diameters, and the remainder comprises a hardenable, flowable, adhesive cement, said hardenable, flowable, adhesive cement comprising a hydraulic cement, an epoxy resin, a phenolformaldehyde resin, a polyurethane resin, or a polysulfide.

Claim 2

A method for insulating and lining a borehole penetrating a permafrost region comprising drilling a borehole through the permafrost region, removing extraneous material from the borehole, flowing a hardenable, flowable composition consisting essentially of a hardenable, flowable, adhesive cement and a divided, solid, close-cell material into the borehole filling said borehole, hardening the hardenable, flowable composition in the borehole, and drilling a smaller diameter borehole through the hardened material to complete the formation of the insulating liner in the original borehole; wherein the divided, solid, closed-cell material comprises as much as about 80 volume percent of the hardenable, flowable composition; and wherein the hardened material forming the liner has a hydrostatic crush strength of at least about 200 psi.

Claim 3

A method for insulating and lining a borehole penetrating a permafrost region comprising forming a liner in situ by hardening in place to form hardened matter a hardenable, flowable composition consisting essentially of a hardenable, flowable, adhesive cement consisting essentially of an epoxy resin plus a hardening agent plus a divided, solid, closed-cell material; wherein the divided, solid, closed-cell material comprises as much as about 80 volume percent of a hardenable, flowable composition; wherein about 10 to 60 volume percent of the hardenable, flowable composition is hollow, siliceous, microspheres having diameters in the range of 1 to 1000 microns and wall thicknesses of 1 to 5 percent of their diameters; and wherein the hardened matter of the liner has a hydrostatic crush strength of about 200 to 15,000 psig.