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API standard class G cement and its inconsistencies in slurry thickening times
A Class G oil well cement conforming to API Standard Specifications was reported to give considerable variation, between batches, in the thickening time of a cement slurry formulation designed for well application. A fundamental study was undertaken on cement obtained from 3 separate batches in an attempt to determine the cause of the variability. The cement was characterized in terms of the chemical and physical properties and found to be within API Specifications: thickening times at 55 °C, and 5200 psi give consistent thickening times of around 99-107 minutes and was well within the 90 -120 minutes limit. When used in a slurry formulated for a well having a bottom hole circulation temperature of 67 °C, the 3 batches of cement give significantly different thickening times ranging from 1090 to 1400 minutes. A baseline was determined on the 3 batches of cements hydrated without additives, and properties of the hydration products determined using SEM, XRD, calorimetry, TGA/DTA and FTIR. The study was then extended to investigate the effect of the cement, first, in combination with the individual additives of the slurry formulation and second, with the complete additive composition. Additives of the slurry formulations included, lignosulfonate based retarder, sulfonated naphthalene formaldehyde condensate dispersant, hydroxyethylcellulose based fluid loss and polyether polyalcohol antifoam agent. Baseline data indicated almost no difference in performance between the 3 batches of Class G cement. Variations in the thickening time observed in the formulated cement slurry were attributed primarily to the interaction with the lignosulfonate retarder though it was not the sole cause. Data suggests that the amount of absorption of the lignosulfonate retarder appear dependent on the specific surface area of the individual cement phases, in particular the alite phase. In addition the lignosulfonate influences the initial development of the ettringite and calcium hydroxide phases and alters the morphology of the C-S-H. Hydroxyethylcellulose component of the fluid loss additive also acts as a powerful retarder though its contribution to the variation between batches is minimal due to the physical rather than chemical process involved. The effects of the sulfonated naphthalene formaldehyde condensate dispersant and the polyether polyalcohol antifoam agent on thickening time were minimal and are only briefly discussed.
API standard class G cement and its inconsistencies in slurry thickening times
A Class G oil well cement conforming to API Standard Specifications was reported to give considerable variation, between batches, in the thickening time of a cement slurry formulation designed for well application. A fundamental study was undertaken on cement obtained from 3 separate batches in an attempt to determine the cause of the variability. The cement was characterized in terms of the chemical and physical properties and found to be within API Specifications: thickening times at 55 °C, and 5200 psi give consistent thickening times of around 99-107 minutes and was well within the 90 -120 minutes limit. When used in a slurry formulated for a well having a bottom hole circulation temperature of 67 °C, the 3 batches of cement give significantly different thickening times ranging from 1090 to 1400 minutes. A baseline was determined on the 3 batches of cements hydrated without additives, and properties of the hydration products determined using SEM, XRD, calorimetry, TGA/DTA and FTIR. The study was then extended to investigate the effect of the cement, first, in combination with the individual additives of the slurry formulation and second, with the complete additive composition. Additives of the slurry formulations included, lignosulfonate based retarder, sulfonated naphthalene formaldehyde condensate dispersant, hydroxyethylcellulose based fluid loss and polyether polyalcohol antifoam agent. Baseline data indicated almost no difference in performance between the 3 batches of Class G cement. Variations in the thickening time observed in the formulated cement slurry were attributed primarily to the interaction with the lignosulfonate retarder though it was not the sole cause. Data suggests that the amount of absorption of the lignosulfonate retarder appear dependent on the specific surface area of the individual cement phases, in particular the alite phase. In addition the lignosulfonate influences the initial development of the ettringite and calcium hydroxide phases and alters the morphology of the C-S-H. Hydroxyethylcellulose component of the fluid loss additive also acts as a powerful retarder though its contribution to the variation between batches is minimal due to the physical rather than chemical process involved. The effects of the sulfonated naphthalene formaldehyde condensate dispersant and the polyether polyalcohol antifoam agent on thickening time were minimal and are only briefly discussed.
API standard class G cement and its inconsistencies in slurry thickening times
API Standardklasse G Zement und dessen Widersprüchlichkeiten bei den Abbindezeiten
Lota, J.S. (author) / Farris, S.R. (author) / Luke, K. (author)
2013
26 Seiten, 17 Bilder, 2 Tabellen, 9 Quellen
Conference paper
English
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