LAUSR

Abstract In this paper, the acceleration performances and mechanisms of chlorides (CaCl 2 , LiCl and KCl) on oil well cement at low temperatures were studied. The results indicated that their accelerating ability follows the order of CaCl 2  > LiCl > KCl. CaCl 2 has some unfavorable effects on the performance of cement, such as increasing the adiabatic temperature, causing bad rheology and thixotropy of cement slurry, and thickening the slurry, which may cause a “flash set”. LiCl can significantly enhance the compressive strength development of oil well cement stone at low temperatures like CaCl 2 , but do not have the disadvantages of CaCl 2 . Besides, LiCl can effectively shorten the static gel strength from 48 Pa to 240 Pa and also have much smaller adiabatic temperature. Based on the micro-test analyses, it was found that LiCl can accelerate the hydration rate of oil well cement under low temperatures. The hydration products of cement slurry include the ettringite (AFt), strip-shaped CSH gel (250–350 nm) and strip-shaped CSH gel (50–70 nm). The small spherical CSH gel fills in the pores of strip-shaped CSH gel to form a dense spatial structure. On contrast, the CSH gel forms a network structure in the cement containing CaCl 2 or KCl. CaCl 2 also inhibits the generation of AFt.