Dual Prevention of Severe Losses of Cement Slurries in Cementing Long Open Holes

Aiming at the cementing problem of long open hole malignant leakage wells, the thermo-sensitive shape memory loss prevention spacer and foam leakage prevention cement slurry were developed, which synergistically reduce the cementing loss risk of long open hole malignant leakage loss wells. The thermo-sensitive shape memory material was developed, which resistance temperature is 150 ℃ and deformation memory temperature is 80～110 ℃, the length of thermo-sensitive shape memory mesh particles after deformation is 10 times that of normal temperature, and the diameter of shape memory expansion ball after expansion is 3 times that of normal temperature. The thermo-sensitive leak-proof spacer was developed, and the bearing-capacity of 3mm crack can reach 8.5MPa. Foaming agent and foam stabilizer were selected, and foam cement slurry were developed, and the density can be adjusted from 1.12 to 1.31 g/cm³, the difference between the upper and lower parts was less than 0.01 g/cm³, and the compressive strength of 1.12 g/cm³ foamed cement stone can reach 6.6 MPa at 30 ℃/72 h, and bubbles in set cement are uniformly dispersed. The spacer duration design method that considering the equivalent plugging time and washing efficiency was established, and the foamed cement slurry section constant gas injection method was formed. Based on thermo-sensitive anti-leakage spacer and foam cement slurry, The leak-proof cementing technology has been applied for 2 Wells, and the one-time sealing section length exceeds 4000 m, and the spacer and cement slurry returned to the surface successfully and got good results.