Anti-Leakage Cementing Technology for the Long Well Section below Technical Casing of Ultra-Deep Wells in the No.1 Area of Shunbei Oil and Gas Field

With a goal of overcoming cementing challenges encountered in drilling the section below technical casing in the No.1 Area of the Shunbei Oil and Gas Field, an anti-leakage cementing technology for long-sealing section was studied. Problems to be overcome included low pressure-bearing capacity of Silurian strata, serious leakage, long sealing section of primary cementing and high leakage rate. Causes were analyzed from geological and engineering aspects, and technical requirements were clarified. High strength hollow glass microspheres were selected as the weight reducer, and a low-density cement slurry was developed based on particle grading principle. Fibers of different sizes in the isolation fluid were used to improve the pressure bearing capacity of formation. In addition, a“normal injection and reverse squeezing”anti-leakage cementing technique was developed to optimize the performance of the liner cementing of long sealing section in ultra-deep wells. The results of laboratory tests show that the density increase of low-density cement slurry was less than 0.03 kg/L under 100 MPa. The cement stone had a good pressure bearing capacity and compressivestrength, which was over 15 MPa. The pressure-bearing capacity of formation was increased by 1.5 MPa by using an anti-leakage spacer fluid. An anti-leakage cementing technique for the long sealing well section below the technical casing in the ultra-deep wells in the No.1 Area of the Shunbei Oil and Gas Field is formed by the combination of“normal injection and reverse squeezing”cementing process, low-density cement slurry, and plugging-type spacer fluid. This technology has been applied in the ϕ177.8 mm liner cementing jobs in more than 10 wells with annulus of those wells thoroughly sealed by cement slurry without leakage section, by which the cementing leakage problem was solved. The results of research and applications show that this technology has achieved a significant anti-leakage effect, and it can effectively solve the cementing problems in this area.