Factors affecting the behavior of bentonite fluids and their in-situ conversion into cement. Final report

To develop a basic understanding of the effects of common salts, hydroxides, and other mud additives on the rheology and other functions of bentonite fluids, bentonite fluids containing these additives were autoclaved at the temperature range 70 to 600/sup 0/F, and under a pressure of 17,000 psi. Subsequently, the high-temperature rheology of the fluids was measured with a FANN 50C viscometer. Other fluid properties such as plastic viscosity, gel strength, yield point, pH, CEC, and fluid losses were also determined before and after autoclaving of the fluids. The high-temperature reactions occurring in these fluids were studied with x-ray diffraction and electron microscopy. Another costly problem in drilling technology is related to the poor cement bonding of the casing to the formation. As a solution to this troublesome situation, the in-situ conversion of bentonite fluids into cement has been studied. This conversion has been successfully achieved by the addition of lime to bentonite fluids at and above 300/sup 0/F.