Patent ID: 6283213
Filing Date: 2001-09-04
Classification: E21B

Abstract:
A method for displacing a drilling fluid from an annular space between the inner surface of a wellbore and the outer surface of a casing positioned in the wellbore with a cement slurry, the method consisting essentially of:a) injecting a spacer fluid consisting essentially of:1) an aqueous lead spacer fluid designed to clean an upper hole section and having a density equal to or greater than the density of the drilling fluid and a viscosity greater than the drilling fluid and containing from about 0.5 to about 10 weight percent of a surfactant consisting essentially of from about 10 to about 90 mole percent of at least one alkyl polyglycoside containing alkyl groups containing from about 4 to about 20 carbon atoms and having an oligomerization number from 1 to about 12 and from about 90 to about 10 mole percent of at least one ethoxylated alcohol containing monofunctional alkyl alcohols containing from about 6 to about 16 carbon atoms and from about 2 to about 8 ethylene oxide groups per molecule of monofunctional alkyl alcohol; and,2) an aqueous tail spacer fluid designed to clean a bottom hole space and having a density equal to or greater than the lead spacer fluid and equal to or less than the density of the cement slurry and having a viscosity less than the cement slurry and containing from about 0.5 to about 5.0 weight percent of a surfactant consisting essentially of from about 30 to about 100 mole percent of at least one alkyl polyglycoside containing alkyl groups containing from about 4 to about 20 carbon atoms and having an oligomerization number from about 1 to about 12 and up to about 70 mole percent and less than in the lead spacer of at least one ethoxylated alcohol containing alkyl alcohols containing from about 6 to about 16 carbon atoms and from about 2 to about 8 ethylene oxide groups per molecule of alkyl alcohol;b) injecting the cement slurry; andc) injecting a chaser fluid in an amount sufficient to displace the drilling fluid, the spacer fluid and at least a portion of the cement slurry from the casing into a selected portion of the annular space.