Study on Performance of Low-Density Cement Slurry at Big Temperature Differences

When cementing a long well section with big temperature difference between the top and bottom of the section in one stage, it is generally difficult for the top cement to develop strengths in a long period of time. Presently studies are focused on the retarders for big temperature differences, other cement additives for big temperature differences and cementing wells with temperature differences bigger than 100℃ receive less attention. To solve problems encountered in cementing wells with big temperature differences between the two ends of the cementing sections, a 1.4 g/cm³ cement slurry with good performance in big temperature differences was developed based on laboratory study on the properties of filter loss reducers, dispersants and retarders at big temperature differences. It was found in the study that the filter loss reducer C-G86L and the retarder C-H42L show very good performance at big temperature differences. Introduction of butylbenzene latex into the cement slurry helps the development of the strength of the set cement at low temperatures. At temperature difference of 110℃, temperature at the top of cement of 20℃, the compressive strength of the set cement in 48 hours reached 5.92 MPa. The cement slurry was successfully used in cementing a well and the job quality was excellent.