Synergistic Effects of Tricalcium Aluminate and Gypsum on Performance of Oil Well Cement Slurries
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摘要: 为促进油井水泥质量控制,采用不同铝酸三钙(C3A)含量的G级油井水泥熟料与不同种类石膏匹配,研究了在80℃下油井水泥中C3A与石膏协同对水泥浆凝结时间、稠化性能、抗压强度、渗透率和水化产物的影响。结果表明,80℃下,水泥中C3A含量越高,凝结和稠化时间越短,高C3A含量有利于水泥石早期强度提升,但会导致后期强度倒缩,油井水泥中C3A含量宜严格控制在3%以内。石膏促进水泥浆的凝结时间,其作用效果为二水石膏>半水石膏>无水石膏,相比于无水和半水石膏,二水石膏使掺有缓凝剂H42L的水泥浆稠化时间更长,且更有利于水泥石抗压强度的发展。80℃下,C3A和二水石膏协同对早期硅酸钙矿相水化具有促进作用,C3A相水化主要生成C3AH6,其生成量与C3A含量和石膏种类密切相关。该研究结果对油井水泥质量稳定性控制和改善固井质量具有重要的理论和参考意义。Abstract: To better control the quality of oil well cement, class G cement clinkers with different contents of tricalcium aluminate (C3A) were mixed with different kinds of gypsums, and study was conducted on the synergistic effects of C3A and gypsum on the gelling time, thickening property, compressive strength, permeability and hydration products of the cement at 80℃. It was found that at this temperature, the higher the C3A content, the shorter the gelling time and thickening time of the cement. High C3A content is beneficial to the enhancement of the early strength of the set cement, the disadvantage of this is that the strength of the set cement in later stage will have a negative growth. To avoid this deficiency, the C3A content in a cement should be controlled to less than 3%. Gypsum in the cement helps extend the gelling time of the cement, in this way the dihydrate gypsum is better than bassanite, and bassanite is in turn better than anhydrite. Compared with bassanite and anhydrite, dihydrate gypsum can extend the thickening time of the H42L (a retarder) treated cement slurry much longer, and the use of dihydrate gypsum is much more beneficial to the development of the compressive strength of set cement. At 80℃, the synergistic action between C3A and dihydrate gypsum promoted the hydration of calcium silicate’s early stage mineral phase, the hydration product of C3A was mainly C3AH6, the amount of which produced was closely related to the content of C3A in the cement and the types of gypsum. The results of this study are of theoretical and referential importance to the control of the quality stability of oil well cement and to the quality improvement of well cementing operation.
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Key words:
- Class G oil well cement /
- C3A /
- Gypsum /
- Thickening property /
- Compressive strength
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表 1 G级HSR油井水泥熟料和二水石膏的化学成分(%)
组分 CaO SiO2 Al2O3 Fe2O3 SO3 MgO K2O Na2O TiO2 LOI C1熟料 62.35 22.34 3.73 4.95 0.46 4.16 0.66 0.14 0.19 0.34 C3熟料 62.24 21.33 4.57 5.81 0.59 2.91 0.72 0.31 0.44 1.11 二水石膏 31.75 2.72 1.02 0.28 41.27 0.98 0.10 0.03 21.64 表 2 G级HSR油井水泥熟料矿相含量(XRD-Rietveld法)(%)
矿物组分 C3S C2S C3A C4AF C1熟料 50.21 24.8 1.47 15.50 C2*熟料 50.51 24.1 2.74 16.51 C3熟料 50.78 23.4 4.00 17.51 注:C2*熟料由50%C1和50%C3掺混获得。 表 3 C3A与石膏协同对油井水泥浆密度、 流动度和凝结时间的影响(80℃)
组别 ρ/
g/cm3流动度/
cm初凝时间/
min终凝时间/
minC1 1.952 15.9 130 150 C1-G 1.959 15.6 105 120 C1-Hemi CS 1.934 15.8 115 135 C1-CS 1.922 15.5 125 145 C2 1.951 15.8 130 145 C2-G 1.941 16.4 100 115 C2-Hemi CS 1.915 15.5 105 125 C2-CS 1.890 16.5 110 135 C3 1.925 16.4 120 140 C3-G 1.914 17.5 95 110 C3-Hemi CS 1.933 17.2 100 120 C3-CS 1.925 16.8 110 130 表 4 C3A与石膏协同对油井水泥石渗透率的影响
组别 渗透率/mD 1 d 7 d 28 d C1-G 3.63 4.27 1.84 C1-Hemi CS 1.49 3.84 1.49 C1-CS 1.49 1.41 1.31 C2-G 3.71 4.10 1.60 C2-Hemi CS 1.63 3.78 1.44 C2-CS 1.55 1.52 1.50 C3-G 2.63 4.77 1.72 C3-Hemi CS 1.91 4.32 1.58 C3-CS 1.78 1.70 1.66 -
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