Study and application of a high temperature and salt-resisting cement slurry system.

A high temperature and salt-resisting cement slurry system was studied to cement long completion intervals based on characteristics of deep wells such as high temperature and productive layers distributing deeply and dispersedly. This system is composed of high temperature filtrate reducer G301 (or G306), high temperature retarder GH-Ⅱ (GH-HB) and high temperature drag reducer USZ. Evaluation tests showed that, the high temperature and salt-resisting cement slurry has excellent salt durability up to saturated salt solution; it works well at temperature lower than 160℃; the set slurry has compressive strength more than 14 MPa after aging at low temperature, and the value is more than 15 MPa even after aging at high temperature. All these data illustrating that the system possesses excellent strength retrieve resistance at high temperature. The rheological property is good, the fluid loss is less than 150 mL, the thickening time is adjustable with short transient time. In addition, this slurry is easy to prepare onsite. Several cementing jobs with the cement slufry in different oilfields were successful with high cementing quality.