The present invention relates to a method of cementing a casing of an oil or gas pipeline to a surrounding well wall, where a hydraulic cement slurry is formed and the slurry is deployed in the annulus between the pipeline casing and the surrounding well wall. The cement slurry is formed by mixing together a hydraulic cement 12 to 24% of silica based on the weight of cement, and water; wherein the silica comprises 1/3 to 2/3 microfine silica and 2/3 to 1/3 silica flour. The invention further relates to a cement slurry for use in the method.
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