关键词: G级油井水泥, 不确定度评定, 固井质量, 稠化时间, 游离液含量, 抗压强度 

Abstract: With the development of metrology，measurement uncertainty has been widely applied to many fields，which reflects the testing level of a laboratory and the reliability of testing results. In order to improve the accuracy of the quality testing data of grade G oil well cement，the testing processes of all physical parameters were investigated and analyzed in respect of testing repeatability，sample weighing，and cement slurry preparation by building a mathematical model. A typical method to evaluate the uncertainty in testing the thickening time，free liquid content and compressive strength of grade G oil well cement was established. The evaluation results show that when the inclusion factor K is 2，and the thickening time of grade G oil well cement is 103.3 min，its spread uncertainty is 1.09 min； when the free fluid content is 3.71%，its spread uncertainty is 0.71%；when the compressive strength at 38 ℃ is 5.44 MPa，its spread uncertainty is 1.23 MPa. The factors affecting the uncertainty in the testing process were determined，which are mainly the testing repeatability of samples，and followed by the mass weighing of samples. In actual testing，the testing error should be minimized by improving the weighing process of the mixed materials and increasing the number of repeated testing of samples. 

Key words: grade G oil well cement, uncertainty evaluation, cementing quality, thickening time, free fluid content, compressive strength