High-temperature-resistant cementing material is required for wells drilled for heavy and shale-oil production by steam injection and in-situ combustion and for deep geothermal wells. Current cementing materials do not meet these requirements. A cementing material with heat resistance up to 600A degrees C, compressive strength exceeding 60 MPa, and elasticity as low as 12 GPa was developed by the author. This material can be used for cementing both oil and gas wells. It can strongly cement formation rocks and well casings.