REVIEW OF THE APPLICATION OF CLAY IN THE DRILLING FLUIDS.

Although water was used initially as the carrying fluid, the advantages of using suspensions of clay in water became apparent as clay minerals were inadvertently incorporated in the fluid as a result of drilling through argillaceous strata. Thus it became the usual practice to add surface clays to water in order to prepare a mud for circulation. Clay-in-water suspensions were also found to impede the loss of fluid into permeable, low-pressure formations. This paper reviews the present status of clay in the drilling fluids with special reference to the petroleum industry. It also touches upon the limitations and constraints in the application of clay for certain drilling operations.