A New Method to Evaluate the Gas Migration for Cement Slurries

Abstract The oil industry wrestled with the problem of gas migration after cementing for many years. As yet an extensive research has been carried out on the problem of gas migration. A lot of corresponding slurries were developed, and most of them have been used successfully in some districts but not total alleviation of the problem. The main reason is the lack of a method to evaluate the gas migration of cement slurries when considering actual well parameters. In this paper, based on previous art of the method to scale-down well parameters to laboratory for more realistic testing of cement recipes, by establishing the method of measuring cement slurries’ static gel strength to gain the development of the annular column hydrostatic pressure, a new method to evaluate the gas migration for cement slurries was developed. This method depends on the decline of upper annular column hydrostatic pressure, and can be used to evaluate the ability of the cement slurry in controlling gas migration. Several cement slurries were investigated by this method. The laboratory tests were presented with good repeatability, and could be used to test the ability of cement slurries in controlling gas migration. In field applications, this method has been used in designing cement recipes when cementing gas wells in Chuanyu Area of China. The ability of cement slurries in controlling gas migration has been tested. The field results were consistent with the laboratory tests, and demonstrated the method could be used to guide cement slurries design effectively.