Spacers and Their Application in Primary Cementing

Many factors are involved in successful completion of a well. It is well accepted that the best cement hob possible is of prime importance. For a good cement job, the contamination of the cement by the drilling fluid should be minimized so that the cement can develop its desired properties. In addition, the drilling fluid should be thoroughly displaced from the annulus so that a competent sheath of cement can form a bond to both the pipe and the formation. When the drilling fluid is not thoroughly displaced, thus allowing commingling with the cementing composition, many undesirable results may occur. Laboratory work and field results show that spacer fluids can be advantageous in assisting in keeping the drilling fluid and cementing composition separated and also aid in more effectively removing the drilling fluid from the annulus. This paper identifies the properties that a good spacer should possess to function properly and discusses general practices in the use of spacers.