Zhu H.-J.,Tianjin Boxing Engineering Science and Technology Company |
Liu A.-P.,Tianjin Boxing Engineering Science and Technology Company |
An S.-H.,Tianjin Boxing Engineering Science and Technology Company |
Xu J.-X.,Tianjin Boxing Engineering Science and Technology Company
Oilfield Chemistry | Year: 2012
Effective evaluation of cement hydrostatic column pressure was critical for the research of cement anti-gas migration. By standardizing methods of measuring cement slurries' static gel strength and weight loss, a new method to evaluate cement hydrostatic column pressure was presented. Cement slurries with two types of fluid loss controller were chosen. The formula of film-forming copolymer slurry was: 100 g G cement, 44 g water, 1. 6 g G60S fluid loss controller, 0. 3 g GF40S dispersant, and that of AMPS copolymer slurry was: 100 g G cement, 44 g water, 3 g BXF-200L fluid loss controller. When measured by pressure-drop instrument ( PDI), the hydrostatic column pressure of two kinds of cement slurry decreased with increasing waiting time. However, when the test instrument was changed to static gel strength analyzer (SGSA), the static gel strength (SGS) of two kinds of cement slurry increased with increasing waiting time. The value measured by PDI was converted to SGS by the formula presented by Sabins, and was compared with the value measured by SGSA. It was found that these two values were close to each other when the cement slurry was in liquid, and after this, the difference increased with increasing waiting time. The differences of these test results obtained were discussed and explained with effective stress principle. The result measured by SGSA was more accurate. The repeatability and operability of this evaluation method were good, which could do some work for the study of gas migration of cementing technology.