Various types of propping agents have been tested in order to evaluate their behaviour at great depth. Several experimental procedures have been used: short duration tests with stress increase at constant temperature, long term tests at constant stress and temperature, tests with simultaneous increase of stress and temperature, with and without continuous flow of water or brine. The behaviour of the proppants having-the "average" density of 3.7 is satisfactory up to a temperature of 100 to 150°C and a stress of 70 MPa.
In order to simulate the steam injection or geothermal, or water producting wells, the propping agents have been tested first without stress at 200°C and 280°C in alcaline solutions at pH chosen from 10,5 to 11,5. At 280°Cthe behaviour of these materials is insufficient at pH 11,5 relatively satisfactory at pH 10,5 for the bauxites having a low silica content. At 200°C a stress of 10 MPa leads to a loss of mechanical strength, Whatever pH may be.