Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe (e.g., casing) is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. Subsequent secondary cementing operations may also be performed.
Cementitious slurries can set very rapidly, e.g., within a few minutes at elevated temperatures with the rate of reaction increasing as the temperature increases. As such, the thickening times of the compositions may be unacceptably short to allow them to be pumped to their desired downhole locations, making the use of such compositions in well cementing a challenge. For example, the drill pipe or the tool used to lower the piping in the wellbore may be cemented in place, causing delay in the completion of the wellbore. One method commonly employed to lengthen the thickening time of cementitious compositions is to introduce set retarders into the compositions, thereby delaying the time to setting of the cement. However, the effectiveness of many set retarders decreases with increasing temperature requiring the use of multiple retarders at varying concentrations. Thus, an ongoing need exists for set retarder compositions that function at elevated temperatures.
USPTO Backgrounds
USPTO Backgrounds