Development and application of curable spacer fluids for adjusting wells in Block Z35

Adjusting wells in Block Z35 of Jiangsu Oilfield are characterized by poor cementation quality and severe oil/gas/water channeling in annular space. These problems were caused predominantly by poor cementation quality on interfaces due to existence of mud cake on sidewall and died mud in borehole. To eliminate them, an innovative curable spacer fluid system was developed, which is mainly composed of suspending agents, curing agents and activator. Test results show that setting stability of the system at 90 ℃ is not higher than 0.01 g/cm3. In accordance with field conditions, 1.40-1.80 g/cm3 curable spacer fluid system with a density of 1.40-1.80 g/ cm3 was prepared. The system has reliable rheological characteristics at 50-90 ℃. Curable spacer fluids with polysulfonate drilling fluid of 0-75% may achieve desirable performances. Cement slurry of Jiangnan Grade G with mixing of 25% curable spacer fluids cured for 48 h at 90 ℃ may have compressive strength up to 16.69 MPa. The newly-developed system has desirable compatibility with drilling fluid and cement slurry. Mixed with cement slurry at different proportions, the system may effective prolong thickening time and reduce filtration loss of cement slurry with minor impacts on initial viscosity of the cement slurry. Through proper adjusting of volumes of weighting materials deployed, curable spacer fluids with densities of 1.4-1.8 g/cm3 can be prepared effectively. Successful application of the system in Well Z35-28 completed with ?139.7 mm tubing casing in Jiangsu Oilfield show the system can enhance displacement efficiency to achieve balanced cementation with effective separation.