Abstract: Mud-To-Cement (MTC) is the technology that may convert drilling fluid to cement slurry by adding cheap blast furnace slag (BFS) and stimulated agent and making use of the properties of fluid loss control and suspension of drilling fluids.As we know, ordinary cement is usually incompatible with drilling fluids and it can cause contamination of cement and has a very bad influence on the performance of cement slurry. A mud-cement system that has 1.50~1.60 g/cm³ n density has been designed. Results of tests and field application indicate that this system has advantages of good compatibility, high
compressive strength and adjustable thickening time. In Zhongyuan oilfield, it was firstly applied in ten wells of the Third Drilling Company and got great success. In this way, the cost of cementing can be decreased greatly. Therefore this technology has been popularized in this area.

Key words: mud-to-cement, well cementing, oil cement, slag cement, polymer