Hydrating cement pastes: Novel rheological measurement techniques of the acceleration of gelation
Schematic of a cementing operating: (a) a section of formation is drilled, (b) a steel casing is lowered into the drilled section, (c) a cement slurry is pumped down the casing, (d) and up the annular space (the cement is pushed by a final brine solution so that the majority of the cement in the steel casing is displaced into the annulus) and allowed to set quiescently, (e) the drill may be reinserted and the next section of well drilled.
Schematic of (a) perforated plate, (b) penetrometer, and (c) detail of penetrometer tip.
(a) Frequency and (b) strain sweeps performed on a 0.40 wt/wt water/cement sample containing 0.25% wt/wt diutan/cement at a constant temperature of . The frequency sweep was done at a constant strain of 0.01%, and the strain sweep at a constant frequency of 1 rad/s. At 8 h, the cement can be seen to yield or slip at high strains. Storage modulus (●, ◼), loss modulus (○, ◻), and complex viscosity for 0 and 8 h, respectively.
Strain sweeps performed at 1 rad/s on a 0.40 wt/wt water/cement sample containing 0.25% wt/wt diutan/cement at a constant temperature of . After 7 h of hydration, the cement can be seen to slip or yield at high strains. Complex viscosity (◼, ◻, ●, ○, ◆, ◇, , , ⬡, and ) at 0,1, 2, 3, 4, 5, 6, 7, 8, and 9 h, respectively.
Effect of varying the wt/wt water/cement ratio (○ 0.25/1, ● 0.30/1, ◻ 0.35/1, and ◼ 0.40/1). Samples were measured at 0.01% strain and 1 rad/s at a constant temperature of .
Rheological data for 0.40 wt/wt water/cement with varying dosages of calcium chloride, measured at 0.01% strain, 1 rad/s, and (◼ 0.0%, ◻ 0.25%, ● 0.5%, ○ 0.75%, ◆ 1.0%, ◇ 1.25%, 2.0%, 3.5%, and 5.0% wt/wt calcium chloride/cement).
Fits of Eq. (1) to the rheological data for various amounts of calcium chloride measured at 0.01% strain, 1 rad/s, and (◼ 0.0%, ◻ 0.25%, ● 0.5%, ○ 0.75%, ◆ 1.0%, ◇ 1.25%, 2.0%, 3.5%, and 5.0% wt/wt calcium chloride/cement).
Plot of , effective acceleration, as a function of dosage of calcium chloride and fit to an exponential curve. Here BWOC represents by weight of cement, or wt/wt calcium chloride/cement. The curve plotted is the fit to Eq. (2):
Penetrometer results for different tip sizes (◼ 9.85 mm, ○ 12.45 mm, and ▲ 18.85 mm), for a sample of 0.40 water/cement, with 0.25% wt/wt diutan/cement. (a) As can be seen, the force curves do not overlap. (b) Once the results are replotted as yield stresses by scaling the forces on the area of the spherical indenter using Eq. (7), the curves collapse. Each curve is the average of two measurements.
Penetrometer results for varying dosages of calcium chloride (◼ 0.0%, ◻ 0.25%, ● 0.5%, ○ 0.75%, ◆ 1.0%, ◇ 1.25%, and 1.5% wt/wt calcium chloride/cement), with yield stresses calculated via Eq. (7) using a measuring tip with a diameter of 12.45 mm.
Oscillatory shear data for a 0.385/1 wt/wt water/solids magnesium oxide paste measured at 1 rad/s using (◼) a 50 mm parallel plate and (◻) the perforated plate tool described above.
Mineralogical composition of Class H oil well cement. Data provided by Scherer et al., Princeton University, Department of Civil and Environmental Engineering.
Particle size distribution for magnesium oxide particles.
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