Anti gas-migration cementing

摘要

A casing or liner in a wellbore penetrating a zone having high formation gas pressure is cemented with a cementitious slurry comprising blast furnace slag. In one embodiment the cementitious slurry is made by combining blast furnace slag and a drilling fluid. Also, a method for plugging or setting sidetracking plugs and other secondary cementing operations in a wellbore penetrating a zone having high gas formation pressure comprising placing a mass of blast furnace slag cementitious slurry at a preselected location and allowing the slurry to set.