Compositions and methods for well completions

摘要

Well-cementing compositions for use in high-pressure, high-temperature (HPHT) wells usually contain a complex array of cement additives, including retarders, dispersants and fluid-loss additives. Under these extreme conditions additive degradation, reactions between additives, reactions between additives and the cement, or combinations thereof may occur—causing slurry gelation, premature setting or both. Incorporation of organoamine compounds in the cement compositions may help prevent or reduce the severity of slurry gelation, setting-time reduction or both.

主权项

1. A method for controlling the rheological properties, the setting time, or both of a cement slurry, comprising:
(i) providing a cement slurry comprising water and Portland cement; and (ii) incorporating one or more organoamine compounds, one or more retarders, one or more borate compounds and at least one fluid-loss additive in the slurry simultaneously during slurry mixing, wherein the one or more organoamine compounds is present at a concentration between 0.2 L/tonne and 5.0 L/tonne of cement slurry, and the one or more organoamine compounds prevents formation of a quaternary gel in the cement slurry, wherein the organoamine compounds are one or more members selected from the group consisting of monoethanolamine, diethanolamine, monoisopropanolamine, diisopropanolamine, monoethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine, and tetraethylenepentamine, wherein the cement slurry has a temperature between 260° C. and 302° C.