Study and application of corrosion-resistant low-density cement system

The mechanism of set cement corrosion is discussed by using phase analysis method in this paper. It is pointed out that the unconsolidated phase and diffusional effect as a result of the action of formation water solution matrix Ca (OH)2 with Ca(OH)2 are the basic reason causing the corrosion of the set cement and casing's exterior wall and a technical idea of using corrosion-resistant cement to from a protection ring to prevent casing's exterior wall corrosion is put forward. A new low-density cement system suited to sealing Luohe formation is developed and, by using it, the difficult problem of casing's exterior wall corrosion in Luohe aqueous layer in Changqing Oil Field is successfully solved, effectively prolonging the production phase of oil and gas wells.