Formation Damage Caused by Cement Filtrates in Sandstone Cores

A series of core damage experiments was conducted with filtrates containing various cement additives, such as dispersants and fluid-loss additives. Results clearly show that the extent and location of the permeability impairment varies, depending on the relative rate of particle precipitation and the residence time in the core. Results of the core-flow experiments are interpreted in conjunction with particle-size distribution and concentration results obtained in batch experiments. In this paper variations in the average particle size and the number concentration of particles with time in various compositions of cement filtrates are reported. These prove to be useful indicators of the extent and location of the damage observed in the cores.