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Abstract

This study considers the improvement of the overall permeability of fractures linking two geothermal boreholes, by means of a chemical leaching. This causes the selective dissolution of one mineral, which produces a permeable channel in the rock, while maintaining adequate rigidity of the matrix, and sufficient chemical inertia to maintain this permeability. A sodium based treatment is suitable in crystalline rocks, such as granite and granodiorite, which contain a sufficient amount of quartz. The reaction products remash in solution, and do not clog the pore spaces; while the relatively slow rate of reaction at high temperatures means that areas relatively far from the fractures are also reached. The selective solution of silica is controlled by adding alcohol, which limits the production of insoluble aluminate gels from aluminium compounds. Suitable results can also be obtained in rocks with a lower quartz content, by alternating acidic and basic leaching. This increased permeability of rocks can be maintained by the injection of sodium chloride solution.

Additional information

Authors: ROQUE C, INSTITUT FRANCAIS DU PETROLE, RUEIL MALMAISON (FRANCE);SARDA J P, INSTITUT FRANCAIS DU PETROLE, RUEIL MALMAISON (FRANCE);GRABIAS J, INSTITUT FRANCAIS DU PETROLE, RUEIL MALMAISON (FRANCE);RENARD M INSTITUT FRANCAIS DU PETROLE, RUEIL MALMAISON (FRANCE), INSTITUT FRANCAIS DU PETROLE, RUEIL MALMAISON (FRANCE)
Bibliographic Reference: EUR 8316 FR (1984) MF, 47 P., BFR 120, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
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