US Patent 7956015 Equivalent circulating density control in deep water drilling

A method of providing a substantially constant rheological profile of a drilling fluid over a temperature range of about 120° F. to about 40° F. includes adding a drilling fluid additive to the drilling fluid, wherein the drilling fluid additive includes the reaction product of a carboxylic acid with at least two carboxylic moieties; and a polyamine having an amine functionality of two or more. A composition, such as an oil based drilling fluid, includes the reaction product of a carboxylic acid with at least two carboxylic moieties and a polyamine having an amine functionality of two or more.