Abstract:

On the basis of the hole-buttom model experiment, this paper studies the damage of mud and cement slurry to foemation. The study shows that the damage of mud is more serious than that of cement slurry. Since the aggressive quantity of cement particles and filtrate is limited by the percolation properties of inner and outer mud cakes and rock core, the damage of cement slurry to formation is therefore decresed. The damage in the area 122 cm inside the wellface is resulted mainly from plugging of grain, while the damage to the formation 2 cm away from the wellface is resulted from the precipitates of filtrate of cement slurry. This paper also analyzes the pollution depth, the filtrate composition, the quantity of precipitates, and the separation sequence.
　

Key words: Formation damage, Pollution zone, Cement slurry, Filtration rate, Filtrate, Grain, Settling