Foamed Cement Slurry Cementing Technology for Low-Pressure and Leakage-ProneLayers of the Shunbei Oil & Gas Field

Permian strata in Shunbei Oil & Gas Field display a high level of fracture development, low bearing capacity, and a high risk of cementing leakage. In order to solve these problems, a protein foam agent and a polymer foam stabilizer with high temperature and salinity resistance were selected. Their dosages were optimized to be 2%–4% and 0.4%–0.8%, respectively, which could make the foam stable at 120 °C. In addition, an anti-leakage foamed cement slurry was developed with adjustable density ranging from 1.10–1.30 kg/L. The slurry has good fluidity, with API filtration of less than 50 mL at 120 °C. The density difference of foamed cement rocks was less than 0.03 kg/L, and the compressive strength of rocks with foamed cement slurry with density of 1.10 kg/L can reach 7.2 MPa after 72 h under low temperature and atmospheric pressure, which showed that the comprehensive performance of foamed cement slurry was excellent. Based on the well depth, temperature and pressure, the annular segmented aeration method was designed, and the aeration volume was adjusted on the fly according to the well depth, cement slurry density, and slurry displacement, which ensures uniform cement slurry density. According to the above results, the foamed cement slurry cementing technology for the low-pressure and leakage-prone layers of the Shunbei Oil & Gas Field was developed and applied in two wells, and the foamed cement slurry was back to the ground successfully, with good cementing quality. This technology supplies a way for the safe and high-quality cementing of low-pressure and leakage-prone formations of the Shunbei Oil & Gas Field and provides a reference for anti-leakage cementing of fractured formations in other blocks.