DRILLING MUD-CEMENT COMPOSITIONS FOR WELL CEMENTING OPERATIONS

摘要

In accordance with the instant invention, there is provided herein a method and composition for drilling and cementing well boreholes in accordance with which a magnesium oxysulfate cement is formed in the drilling mud. Disclosed by this invention is a method and composition wherein the drilling fluid is transformed into a cementitious mass of magnesium oxysulfate cement thereby increasing the compatibility of the ementing composition with the drilling fluid and improving the cement bond to the face of the borehole. This is accomplished by forming a magnesium oxysulfate cement from a magnesium inorganic salt-based drilling fluid to produce an economical and sufficiently strong expansive cement having acceptable setting time for well cementing purposes. The cement compositions may be formed using water or brine solution rather than mud if desired. Hence, brine or water may be added as desired to modify the viscosity characteristics of the cement.