CEMENTING TECHNIQUE WITH BI-BASE BI-SETTING CEMENT SLURRY SYSTEM

The formation pore pressure coefficient is very low in such blocks as Huatugou, Shizigou and Qigequan in Qinghai Oilfield, and lost circulations of different degrees, poor isolations and sometimes as worse as production zone abandonment take place during drilling. According to the geological characteristics of the three blocks, and by careful analyzing of the acoustic amplitude data of the completed well in this area, the conventional cement slurry system is modified based on many experiments. A novel cementing technique of using bi-base and bi-setting cement slurry system is developed, i.e., in the upper lost circulation interval, foam cement slurry is used with retardant, while conventional cement slurry with accelerator is used in the lower production zone. This technique has been field used in 18 wells, and remarkable improvement in cementing quality has been obtained.