Study on a Low Density Cement Slurry Capable of Preventing and Stopping Mud Losses and the Use of the Slurry

The well Yuejin-3-3XC is drilled to a measured depth of 9,432 m, with length of the horizontal section exceeding 3,400 m. This depth and length of horizontal drilling has broken the record of the longest horizontal section in the deepest and ultra-deep horizontal drilling in Asia. The well Yuejin-3-3XC penetrated formations with complex geologic characteristics, and was difficult to drill. Requirements for the properties of cement slurries are high; high temperature, high pressure, low pressure bearing capacity of the formations drilled have all to be considered to avoid losses of the cement slurries. To deal with these difficulties, three low density cement slurries, which are C-Lo PSD (1.30 g/cm³), C-Lite STONE (1.60 g/cm³) and C-Hi PSD (1.40 g/cm³), are formulated. These cement slurries can be used in medium-low and high temperature conditions, and have been successfully used in cementing the well Yuejin-3-3XC. Compared with the cement slurries previously used, these three new slurries have mixing efficiency, rheology, suspension stability and compressive strength of set cement that are significantly improved. Among the three cement slurries, the C-Lite STONE (TBHC = 75 ℃/TTOC = 30 ℃) and the C-Hi PSD (TBHC = 145 ℃/TTOC = 105 ℃) have the strengths of the top slurries in 48 h of 81 MPa and 14.3 MPa under the temperature differences of 45 ℃ and 40 ℃, respectively. During drilling operation, the well Yuejin-3-3XC has encountered several times of mud losses. Use the self-made new lost circulation materials C-B62 and C-B66, the fractures into which the mud was lost were successfully sealed off, ensuring the smooth progress of the cementing operation.