Ultra-Low Density and Low-Friction Cement Slurry Cementing Technologies in Long Sealing Sections of Fuman Oilfield

This paper aims to solve the technical problems of long open hole section, low leakage pressure, low success rate of one-time return of cement slurry of 1.35 kg/L, poor rheological property and stability of cement slurry, and the slow development of early strength in the second-opening cementing of Fuman Oilfield in the Tarim Basin. The low-friction and ultra-low density cement slurry system of 1.20 kg/L was developed based on the theory of close packing design by studying the reinforcing agent for low-density cement slurry and optimizing the pressure-resistant and light material, the low-viscosity fluid loss agent, and high-efficiency comb-type polycarboxylate drag reducer, etc. The settlement of the system was stable and lower than 0.02 kg/L, K≤0.5 Pa·sⁿ, n≥0.8; the 24 h bottom compressive strength was larger than 7.5 MPa, which was more than 50% higher than that of the traditional low-density cement slurry system and met the requirements of performance and mechanical properties for long sealing section, high temperature and high pressure, and easy leakage well. The field application of three wells has achieved good results, with an average pass rate of 88.0%. The research and field application show that the ultra-low density and low-Friction Cement Slurry can provide support for the safe and efficient development of Fuman Oilfield.