The make up water is one of the main building blocks of the drilling mud. The pH, hardness, and salt content of the make up water determine the yield and performance of the bentonite clay. hydration and dispersion of dry clay are greatly affected if the makeup water contains salt or various metallic ions. Many drilling muds are prepared with seawater for economy and convenience. This research study therefore details a comparative study of different salts namely sodium chloride, potassium chloride and calcium chloride on the hydration of bentonite. The rheological values were determined using FANN viscometer with different concentrations of NaCl, KCl and CaCl2((0%,0.5%, 1.0%,1.5%,2.0%, 2.5%, 3.0%, 4.0%, 4.5% and 5.0%) respectively by weight of bentonite. Test results indicated that plastic viscosity for NaCl, KCl and CaCh ranged from 11 to 5 cP, 9 to 8 cP and 9 to 4 cP respectively. Also the yield point ranged from 13 to 2 lb/100ft2,17 to 8 lb/100ft2 and 17 to 1lb/100ft2 respectively. The fluid loss also ranged from 15 to 20ml/30mins for NaCl, 12 to 16ml/30mins for KCl and 18 to 30ml/30mins for CaCh respectively. Test results indicated that increase in the concentration of the salts resulted to decrease in rheological properties and increase in fluid loss respectively. The effect was more pronounced with CaCl2 than the other two salts. It is imperative to introduce fluid loss and viscosifying additives when using mix water with high salt concentrations.

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