Study on performance of hole sealing retarded cement slurry in ultra-deep freezing holes

According to the problem of the water leakage in bottom hole and other parts of shaft lining after vertical shaft with freezing con-struction thawed,the retard ed cement slurry was used to prevent shaft leakage accident effectively. According to special requirements of theretarded cement slurry,which included liquidity,condensati on time,stability and set strength in the frozen vertical shaft construction,a composite high performance retarder which named JS-1 by additive compound technology and C ontrast tests was developed. The re-sults showed that the composite high performance retarder completely met the requirements of the ultra-deep freezing hole which coul d en-sure the cement stable and make the initial setting time up to 40 hours. When the water-cement ratio reduced form 1.0 : 0.8to 1.0 : 1.4,the set strength could be i ncreased from 5 MPa to 12 MPa,which was benefit to improve the sealing quality of ring space between thepipe and the surrounding,and the effect of vertical shaft leakag