Investigations into the standardization, selection and placement of cements for deep boreholes in North Germany

摘要

A description is given of some project-related investigations for determining the optimum cementation system for salt-containing formations, for thermal treatment and in the presence of corrosion stresses in deep boreholes. The mix formulation of the cement suspension and the method of placement under borehole conditions are critical for the quality of cementation. The pumpability of the suspension and the strength and soundness of the resulting hardened cement paste are important. Suspension density and strength are regulated by reactive or inert mineral aggregates. The resistance of the cementation to aggressive media in the surroundings of the borehole require a certain impermeability and material composition of the hardened cement paste. It is the aim of every cementation project that the suspension which has been prepared above ground has the same quality when it is placed underground. It is therefore necessary to ensure that where there is sequential pumping the cement suspension is not mixed with the drilling mud suspensions used beforehand. The actual borehole parameters of depth, formation (surroundings of the borehole), volume and temperature must also be known in advance. The composition of the cement suspension and its setting time then have to be adjusted to suit them.