In 2017, Vietsovpetro switched to G cement brand for casing the strings/liners. For further improvement of casing quality, Vietsovpetro completed the research studies on justifying the selection of effective chemicals, as well as the lab tests with the use of gas migration control additives BA-58L and BA-86L and expanding additive EC-2 in the cement slurry. Initially, the formulations provided by Baker Hughes – BJ with expanding additive EC-2 and gas mitigation control additives based on fine-grained silica (BA-58L) were tested. Later on, this formulation was handed-over to Vietsovpetro laboratory for checking and adjusting; besides, the research scope was expanded by changing the range of EC-2 additive concentration. The researches of the liquid-rubber based additive, BA-86L, were performed the same way. The tests revealed that adding EC-2 in concentration of 0.5% leads to a double increase of cement stone expandability, while concentration of 0.75% to only 20%, which proves unviability of increasing the concentration to 1.0%. To determine a sensibility to gas migration during a cement slurry thickening, the tests with an application of cement hydration analyzer were performed. The tests results led to a definitive conclusion on good anti-gas migration properties of the composition with BA-58L additive. Similar results were obtained for the formulations with BA-86L additive. Therefore, two alternative formulations of cement slurries with expanding and gas migration control additives were developed. These formulations fit the category of tolerant to gas penetration and migration compositions. The tests during the production strings cementing in 2021 proved the efficiency of the developed formulations.
References
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