Patent ID: 6315042
Filing Date: 2001-11-13
Classification: C04B,C09K,Y10S

Abstract:
A method of cementing a pipe string in a well bore containing oil-based drilling fluid with a cement composition comprising the steps of:(a) preparing an oil-based settable spotting fluid composition comprised of oil, an emulsifying surfactant for emulsifying said oil with water whereby an oil-external emulsion is formed, a de-emulsifying surfactant which de-emulsifies said oil-external emulsion when the emulsion is contacted with external water, a hydraulic settable component selected from the group consisting of ASTM Class C or the equivalent fly ash and ASTM Class F or the equivalent fly ash together with a source of calcium and water selected from the group consisting of fresh water and salt water present in an amount sufficient to form a slurry having a density in the range of from about 12 to about 15 pounds per gallon;(b) pumping said settable oil-based spotting fluid composition into said well bore to displace at least a portion of said drilling fluid out of said well bore thereby preventing said drilling fluid from remaining in fractures or other permeable zones in said well bore and progressively increasing in gel strength over time therein;(c) running said pipe string to be cemented into said well bore whereby said pipe string and well bore are at least partially filled with said settable spotting fluid;(d) pumping and displacing said cement composition through said pipe string and into the annulus between said pipe string and the walls of said well bore whereby said drilling fluid and said settable spotting fluid composition in said pipe string and said annulus are displaced therefrom except for portions of said settable spotting fluid composition which may remain in fractures or other permeable zones therein; and(e) allowing said cement composition in said annulus and any settable spotting fluid composition remaining in said fractures or other permeable zones therein to set into hard impermeable masses therein.