Laboratory Research on 0.9 g/cm³ Ultra-Low Density Cement Slurry

Well cementing with low-density cement slurries is faced with many challenges. By analyzing the requirements of cementing wells with ultra-low formation pressures, an ultra-low density cement slurry was formulated with class C cement, a filter loss reducer C-FL712L and a high performance strengthening material BT5. Laboratory test showed that the cement slurry, with density being adjustable between 0.9 g/cm³ and 1.1 g/cm³, has good overall performance. The slurry has good stability, the density difference between the top and the bottom of a slurry column can be controlled within 0.05 g/cm³. The thickening time of the cement slurry is adjustable. The compressive strength of the set cement at 60℃ can be 7 MPa or higher. The gel strengths of the cement slurry develop fast, and is beneficial to the prevention of gas-channeling. This cement slurry can be used in a wide range of pressures and satisfy the needs of cementing reservoirs and ultra-long sections with low pressures in which mud losses are frequently encountered.