Prediction of thickening time of well cements from Blaine air permeability

Abstract

The following measurements were made on API Class A, G, and H cements: thickening time, compositional analysis in terms of oxide and potential phase concentrations, Blaine fineness, and particle size distribution from which a surface area could be calculated. Regression analysis showed that ∼80 % of the variation in the thickening time measurements of Class G and H cements could be explained by either the calculated surface area, mass percentage of particles having an effective diameter less than 3 μm, or Blaine fineness. Multiple regression analysis using compositional variables did not significantly improve the ability to predict thickening time from the easily measured Blaine data. The relatively low standard error of the regression estimate suggested that Blaine fineness should be considered as an addition to other API specification tests for Class G and H well cements. The API thickening time specification test of 90 to 120 min corresponds to a Blaine fineness of 297 to 246 m 2/kg using the regression equation developed for Class H cements.