| Abstract:It is difficult to top fill cementing in the lost circulation formation for geothermal wells because the squeezed cement slurry often deviates from the design position, resulting in cementing failure. The technical idea of top fill cementing in the lost circulation zone is proposed. The fluid column pressure in the well is balanced with the formation fracture pressure to effectively control the moving position of the cement slurry column, and the cement slurry is prevented from being diluted by controlling the displacement of squeeze injection. Both of open cementing and closed cementing methods can be used. For The former, the cement slurry column moves down a long distance during the balancing process and is easily diluted, and the position of the slurry column is difficult to control, which can be used for the conditions with small difference between upper and lower casing, especially in the casing of the same level. For the latter, special sealing tools shall be used to seal the lower casing. The upper and lower well-bore are impassable during cementing, avoiding the disadvantages of long downward distance of cement slurry column, difficult position control, easy dilution, etc., which is suitable for cementing under various casing grading conditions, especially for the larger casing grade difference. |