Study And Application On Cementing Technology For Low Pressure Lost Circulation Wells In East Sichuan

The average well depth in East Sichuan Province reaches up to 6000m, and its complex geology is characterized by multi variable pressure gradient. In Qianfoya Group and Xujiahe Group, there are very low formation fracture pressure layers or faults existed, which leads to lost circulation during drilling and cementing operations. The cementing quality can not be assured as well.In this paper, an extender which could improve compressive strength of is introduced into conventional low density slurry which is composed with cement, microsilicate and microsphere as well. Other additives for adjusting slurry performance are also optimized and high strength low density slurry system ranged between 1.20 g/cm3 and 1.50g/cm3 is worked out. On the other hand, cementing technology is studied to perfect the operation, including balanced pressure engineering design, preliminary lost circulation control, technically prevent leakage, dual or multi set slurry system design, casing running process control or drilling fluid optimization, etc., to minimize formation pressure differential and finally control the lost circulation.Field application in Dingshan 1 Well, Heichi 1 Well, and Puguang 4-2 wells demonstrated that the combination of high strength low density slurry system with matched cementing technology and measures improved cementing quality apparently.