Laboratory data are presented showing that lime muds utilizing a polysaccharide deflocculant are very effective in combating dispersion of shale particles when compared to several commonly used types of water based muds. Similar studies using Wyoming bentonite particles are reported snowing that potassium hydroxide results in less clay dispersion than sodium hydroxide when used for alkalinity control of a lime mud deflocculated with polysaccharide. While the potassium is shown to be reactive with clay particles, the presence of lime in the mud leaves more potassium ion available to react with shale exposed in the wellbore and protect against borehole instability.

Field results are reported showing that potassium ion concentrations of 1,000 to 4,000 mg/L have been adequate in potassium/lime muds containing polysaccharide deflocculant to provide good borehole stability and low mud maintenance costs.

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