Mud Condition Effect on Cement Job Performance

The predominant cause of cementing failure appears to be channels of gelled mud remaining in the annulus after the cement is in place. If mud channels are eliminated, any number of cementing compositions will provide an effective seal.In evaluating factors that affect the displacement of mud, it is necessary to consider the condition of drilling fluid before cement job. Model studies reveal that any decrease in viscosity of the drilling fluid increases the displacement efficiency. The drilling fluid removal is affected by two major downhole conditions, namely, the thixotropic properties of the drilling fluid (very closely related to the gel strength) and its filter cake deposition characteristics.This paper looks at a range of specific mud properties which has a bearing on mud removal during cement job.