Abstract: During the large diaphragm wall construction, it is necessary to increase the specific gravity of the newly made drilling slurry after a long time of rest to maintain the stability of the borehole. Two slurry weight increasing agents, iron powder and barite powder, respectively, are selected for comparative study. The effects of type, content and particle size of the weight increase agent on the specific gravity, viscosity, mud cake thickness, colloid ratio and filter vector of the drilling slurry are evaluated. The results show that iron powder and barite powder have certain effects on gravity, viscosity, mud cake thickness and filter vector of the drilling slurry but have little effect on colloidal ratio of the slurry. The specific gravity gain effect of iron powder on the drilling slurry is more obvious than that of barite powder, which can increase the specific gravity of drilling slurry by 5.7%~10.5%. The slurry viscosity increases with the increase of weight booster content, and the influence of barite powder on the slurry viscosity is the most obvious, and the influence range is about 0.1205/ (s/g) ~0.8165/ (s/g). The particle size of the thickener mainly affects the slurry viscosity, mud cake thickness and filter vector, and these three performance indexes increase with the increase of the particle size of the thickener but have almost no effect on the specific gravity and colloid ratio of the drilling slurry.

Key words: Drilling Slurry, Slurry Water Ratio, Performance Test, Laboratory Test, High Specific Gravity Slurry