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Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries
Egyptian Journal of Petroleum xxx (2018) xxx–xxx
Contents lists available at ScienceDirect
Egyptian Journal of Petroleum journal homepage: www.sciencedirect.com
Full Length Article
Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries I. Aiad a, A.M. El-Sabbagh b, A.I. Adawy c,⇑, S.H. Shafek d, S.A. Abo-EL-Enein e a
Head of Petrochemicals Department, Egyptian Petroleum Research Institute, Egypt Director of Egyptian Petroleum Research Institute, Egypt c Surfactants Laboratory, Petrochemicals Department, Egyptian Petroleum Research Institute (EPRI), 1-Ahmed El-Zomor St., Nasr City, Cairo 11727, Egypt d Surfactants Laboratory, Petrochemicals Department, Egyptian Petroleum Research Institute, Egypt e Chemistry Department, Faculty of Science, Ain Shams University, Egypt b
a r t i c l e
i n f o
Article history: Received 4 January 2018 Revised 4 March 2018 Accepted 18 March 2018 Available online xxxx Keywords: Superplasticizers Rheological properties Apparent viscosity Plastic viscosity Yield stress
a b s t r a c t Three superplasticizers namely: cyclohexanone glyoxylic sulfanilate (CGS), acetone glyoxylic sulfanilate (AGS) and melamine glyoxylic sulfanilate (MGS) were prepared and characterized using FT-IR. The prepared admixtures were evaluated as additives for improving the rheological properties of oil well cement. The effect of temperature (25°, 45° and 65 °C) and admixture dose (0.25, 0.5, 0.75 and 1%) were determined on the apparent viscosity, plastic viscosity and yield stress. The results showed that the prepared superplasticizers, CGS, AGS and MGS decreased these parameters. The results concluded that the CGS, AGS and MGS admixtures act as retarders and dispersant for oil well cement. The three prepared admixtures exhibited high enhancement on the rheological properties which mean that it can use in oil cementing processes. Ó 2018 Egyptian Petroleum Research Institute. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction Oil well cement has been used in underground casing in oil and gas wells [1]. Cement slurry is placing in the annulus space between the geological formations surrounding to the well bore and well casing [2]. Oil well cementing was introduced in the twenties of the last century [3] with a number of objectives: to protect oil producing zones from water flow, to collapsing protect the well casing under pressure, to protect wells from corrosion and to protect ground water from oil and gas contamination [4,5]. OWC chemical composition is slightly different from that of regular Portland cement by lower C3A contents, are coarsely ground and have special retarders such as starch, sugars, etc, in addition to or in place of gypsum [6]. The American Petroleum Institute (API) Specifications for Materials and Testing for Well Cements [7] include requirements for eight classes of OWCs (classes A through H). A wide variety of chemical admixtures is currently available to enhance the OWCs physical properties such as fluidity and workability to achieve successful cementing process and required
Peer review under responsibility of Egyptian Petroleum Research Institute. ⇑ Corresponding author. E-mail address: [email protected] (A.I. Adawy).
compressive strength. They are adsorbed on the cement particles and act as dispersants by electrostatic and/or steric repulsion effects as demonstrated by Uchikawa et al. [8]. The admixture type and its chemical composition, dosages and the molecular structure of the admixtures [9,10] all of these parameters effect on workability of cement. In addition to the chemical composition of cement, especially the amount of C3A and the availability of sulfate attack during early hydration [11] also effect on the cementing process. So, the selection of the most suitable type and the optimum dosage of admixture in cement technology have increasing the importance [12,13]. The rheological properties of oil well cement (OWC) slurry determines the quality of the final product and helps predicting its end use performance and physical properties during and after processing. The rheology of OWC slurries is generally more complicated than that of conventional cement paste. The enhancement in the rheological properties of cement pastes depends on the cement composition and delaying addition time [14–16]. In order to deal with bottom whole conditions (wide range of pressure and temperature). This study aim to prepare three superplasticizers, CGS, AGS and MGS and studying their influence on the rheological properties of the oil well cement slurries. Also, the plastic viscosity and yield stress were determined.
https://doi.org/10.1016/j.ejpe.2018.03.011 1110-0621/Ó 2018 Egyptian Petroleum Research Institute. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011
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I. Aiad et al. / Egyptian Journal of Petroleum xxx (2018) xxx–xxx
2. Materials
solution of polycondensation product, solid content of 40.9 wt%, was cooled to 25 °C.
2.1. Cement 2.3. Mixing and preparing cement slurry A freshly produced sample of class G moderate sulfate resistant oil well cement supplied by Schlumberger Company, Egypt was used. Its chemical composition was found to be: CaO, 60.4%; SiO2, 20.2%; Al2O3, 2.2%; Fe2O3, 2.7%; MgO; 6.0%; SO3, 3.0%; total alkali expressed as Na2O, 0.75%; insoluble residue, 0.75% and loss on ignition, 3%. The specific surface area as determined by the Blaine air-permeability method was found to be 3000 cm2/g. 2.2. Synthesis of superplasticizers 2.2.1. Sulfanilic acid-cyclohexanone glyoxylic condensate 270 g of water and 122.1 g (1.649 mol) of 50% aqueous glyoxylic acid are introduced into 1 L reaction vessel with a thermometer, stirrer, reflux condenser, pH equipment and dropping funnel. 123.4 g of 50% aqueous caustic soda was added while the contents of the vessel were stirred, and the pH was adjusted to 4.0. The temperature was raised to 50 °C and 133 g of cyclohexanone (1.00 mol) was added with continuous stirring. The contents of the vessel were stirred at 50 °C for further 75 min. until the original suspension was turned into a clear solution. The pH was raised during this time to 5.9. While cooling the solution, 88 g (0.509 mol) of sulfanilic acid and 48 g of 20% caustic soda were added simultaneously, this caused the pH dropped to 5.2. The reaction mixture was stirred at 90 °C until a final viscosity of 5.52 cSt (20 wt% solution at 20 °C) was obtained. The pH was adjusted to 10.0 by adding 39.2 g of 50 °C caustic soda to the reaction mixture. The clear aqueous solution of polycondensation product, with a solid content of 40.9 wt%, was cooled to 25 °C [17]. 2.2.2. Sulfanilic acid-acetone glyoxylic condensate 244.1 g (1.649 mol) of aq. glyoxylic acid (50%) and 270 g of water were added to a 1 L reaction flask with a three neck, reflux condenser, stirrer and dropping funnel. 123.4 g of 50% aq. NaOH was added with stirring and the pH was adapted to 4.0, the temperature was adjusted to 50 °C and 116 g of acetone (2.00 mol) was added with continuous stirring for 75 min. till the mixture was turned to a transparent solution. The pH was ascent during this period to 5.9. After cooling, 88 g (0.509 mol) of sulfanilic acid and 48 g of 20% aq. NaOH were added simultaneously, which caused the pH dropped to 5.2, the vessel content was stirred at 50 °C till obtained a viscosity of 5.52 cSt (20 wt% solution at 20 °C). Then the pH was adjusted to 10.0 by adding 39.2 g of 50% NaOH. 2.2.3. Sulfanilic acid-melamine glyoxylic condensate 270 g of water and 244.1 g (1.649 mol) of 50% aqueous glyoxylic acid were introduced into a 1 L reaction vessel with a thermometer, stirrer, reflux condenser, pH equipment and dropping funnel. 123.4 g of 50% aqueous caustic soda was added while the contents of the vessel were stirred, and the pH adjusted to 4.0. The temperature was raised to 50 °C and 126.1 g of melamine (1.00 mol) added with continues stirring. The contents of the vessel were stirred at 50 °C for a further 75 min until the original suspension was turned into a clear solution. The pH was raised during this time to 5.9. While cooling the solution, 88 g (0.509 mol) of sulfanilic acid and 48 g of 20% caustic soda were added simultaneously, this caused the pH dropped to 5.2. The reaction mixture was then stirred at 50 °C until a final viscosity of 5.52 cSt (20 wt% solution at 20 °C) was obtained. The pH was adjusted to 10.0 by adding 39.2 g of 50% caustic soda to the reaction mixture. Then the clear aqueous
The blender type mixer was used to prepared cement slurries according to the following procedure. The required water and the quantity of liquid admixture were poured into the blender. At a slow speed the mixing started for 15 s to disperse the chemical admixtures thorough the water. The cement was added to the admixed liquids over a period of 15 s. by a rubber spatula manual mixing was continued for 15 s to ensure homogeneity of material sticking to the mixing container wall. Finally, for another 35 s the mixing resumed at high speed. For all cement slurries the mixing procedure was strictly followed. All mixing was conducted at a controlled ambient room temperature of 23 ± 1 °C. The total time between the beginning of mixing and the start of the rheological tests was kept constant to avoid the effect of exogenous variables on the results. The rheometer set-up was also maintained constant for all slurries. The concentric cylinder test geometry was kept at the test temperature so as to avoid sudden thermal shock of the slurry. Cement slurries used in this study were prepared using moderate sulfate-resistant Class G oil well cement with a specific gravity of 3.15. The Distilled water was used for the mixing, and its temperature was maintained at 23 ± 1 °C using an isothermal container. A number of conventional chemical admixtures along with new-generation admixtures were used and their effects on the rheological properties of cement slurries at different temperatures were evaluated. These three synthetic admixtures sulfanilic acid-cyclohexanone glyoxylic (CGS), sulfanilic acid-acetone glyoxylic (AGS) and sulfanilic acid-melamine glyoxylic (MGS), (Scheme 1) were used by four different dosages 0.25%, 0.50%, 0.75% and 1% of weight of cement. 3. Results and discussion 3.1. Chemical structure The chemical structure of the prepared admixtures was confirmed by FTIR spectra. 3.1.1. FTIR spectra The FTIR spectra of the synthesized admixtures as shown in Fig. 1 showed the following absorption bands as shown in Table 1. IR spectra are represented in Fig. 1 referring to the hydrogen bonding intermolecular in the solid materials as the result of the coiling form of the polymer molecules. In all synthesized superplasticizers spectra, the characteristic absorption of the ether linkage (CAOAC) formed due to condensation of methylol groups, however, C@N stretching band in MGS appears at 1603 cm 1. The FTIR spectra confirmed the expected functional groups in the synthesized admixtures. 3.2. Effects of temperature and chemical admixtures on apparent viscosity The apparent viscosity results of OWC slurries at a shear rate of 31 s 1. A shear rate of 31 s 1 was chosen since it was the mean shear rate used in the experimental program. The apparent viscosity for cement slurries incorporating various dosages of CGS at different temperatures was presented in Fig. 2. It can be observed that the apparent viscosity decreased with increased CGS dosage at all investigated temperatures except 0.25% dosage showed increasing of apparent viscosity than blank. However, apparent viscosity values at 25 °C reached lower values
Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011
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NH2
COONa
O
COONa
*
*
O
SO3Na
n
O
Cyclohexanone glyoxylic sulfanilate (CGS)
NH2
COOH
*
O
O
CHO
O
COONa
COONa
*
NH2 CH3 H3C
NaOH
SO3Na
n
SO3H
Acetone glyoxylic sulfanilate (AGS)
NH2 N H2N
N N
NH2
NH2 O
H N
COONa
COONa
*
*
N N
SO3Na
NH N
NH2
n
Melamine glyoxylic sulfanilate (MGS) Scheme 1. Synthetic route of CGS, AGS and MGS superplasticizers.
at higher CGS dosage. It appears that CGS acted as an accelerator at low dosage and as a retarder and dispersant at higher dosage. Apparent viscosity values of OWC slurries incorporating various AGS dosages is presented in Fig. 3. It can be observed that the apparent viscosity generally decreased with the increase of AGS dosage, and increased significantly with increasing the temperature. At 65 °C, no significant change in apparent viscosity was evident between dosages of 0.25 and 0.5%, but beyond this level the apparent viscosity decreased sharply. A sharp decrease in apparent viscosity was observed at dosage 0.75% and 1%. A similar trend was observed in the case of yield stress for OWC slurries. It appears that AGS acted as a retarder and dispersant at all dosages. Fig. 4 illustrates the apparent viscosity at different temperatures for cement slurries incorporating various dosages of MGS. It can be observed that the apparent viscosity decreased with increased MGS dosage at all investigated temperatures. It appears that MGS acted as a retarder and dispersant at all dosages.
3.3. Effects of temperature and chemical admixtures on yield stress Fig. 5 illustrates the yield stress values for OWC slurries incorporating various dosages of CGS at different temperatures. It can be observed that yield stress decreased significantly with increasing CGS dosage regardless of the temperature. The rate of decrease in yield stress was steeper at higher temperature. The differences between yield stress values measured at different temperatures (25 °C, 45 °C and 65 °C) decreased with higher dosage of CGS. Moreover, the higher the temperature, the higher was the admixture saturation dosage. The yield stress values of cement slurries incorporating various dosages of AGS and MGS are presented in Figs. 6 and 7. Yield stress values increased significantly with increasing temperature and decreased slightly with increasing admixture dosage. At 25 °C, the yield stress showed a sharp drop when the dosage increased from 0.50% to 1.00%. Beyond this dosage, there was no noticeable change in yield stress. At 65 °C a gradual decrease in yield stress
Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011
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I. Aiad et al. / Egyptian Journal of Petroleum xxx (2018) xxx–xxx
Fig. 1. FT-IR spectrum of: a) AGS, b) MGS.
Table 1 IR Characteristic bands of the synthesized superplasticizers. Compounds Band (cm
1
)
NH2 stretching CAOAC stretching C@O stretching C@N stretching C@C stretching S@O stretching CAH symmetric Stretching aliphatic
AGS
MGS
3376 1036–1185 1707 – 1514–1608 1392 –
3384 1033–1177 1571 1603 – – 2862
with increasing AGS and MGS dosage was observed. This is likely due to the fact that a higher AGS and MGS dosage offset the acceleration of hydration due to higher temperature. 3.4. Effects of temperature and chemical admixtures on plastic viscosity The plastic viscosity at different temperatures of OWC slurries incorporating different dosages of various admixtures was determined from the slope of the shear stress-shear strain down curve. The measured plastic viscosity does not always truly represent the material properly and sometimes could be misleading because of the high error involved in the fitting curve to the Bingham model. However, plastic viscosity was measured and presented in this
Fig. 2. Apparent viscosity of oil well cement slurries at various temperatures and different dosages of admixtures of CGS (w/c = 0.40).
section because it is very difficult to create mechanical models for the deformation behaviour of cement paste using the apparent viscosity at each shear rate point. As shown in Fig. 8, the plastic viscosity at 0.25% show a significant increasing with CGS dosage at all investigated temperatures. The sharply decrease showed at 0.5% then the plastic viscosity values gradually decrease with increasing CGS dosages. Also, the plastic viscosity at different temperatures for cement slurries incorporating various dosages of AGS and MGS is illustrated in Fig. 8.
Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011
I. Aiad et al. / Egyptian Journal of Petroleum xxx (2018) xxx–xxx
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Fig. 3. Apparent viscosity of oil well cement slurries at various temperatures and different dosages of AGS admixture (w/c = 0.40).
Fig. 6. Yield stress of oil well cement slurries at various temperatures having different dosages of AGS admixture (w/c = 0.40).
Fig. 4. Apparent viscosity of oil well cement slurries at various temperatures and different dosages of MGS admixture (w/c = 0.40).
Fig. 7. Yield stress of oil well cement slurries at various temperatures having different dosages of MGS admixture (w/c = 0.40).
Fig. 5. Yield stress of oil well cement slurries at various temperatures and different dosages of CGS admixture (w/c = 0.40).
It is shown that plastic viscosity decreased with the increase of AGS or MGS dosages, and increased significantly with increasing the temperature at low AGS and MGS dosages. However, plastic viscosity values at all tested temperatures reached comparable values as the AGS and MGS dosages increased. As mentioned earlier, the rheology of OWC slurries depends on a number of factors, such as cement hydration kinetics, supporting liquid rheology, inter-particle forces, and solid volume fraction [18]. A number of chemical admixtures such as plasticizers/water reducer (dispersants), retarders, weighting agents, extenders, etc, have been used to modify the rheological properties of OWC slurries for proper placement in deep and narrow oil well annulus.
Most water reducing admixtures retard the cement hydration rate in addition to acting as a deflocculant due to electrostatic repulsion, steric repulsion, or both [19]. Moreover, the performance of chemical admixtures also depends on other factors including the type of cement and its fineness, nature and amount of calcium sulfates and soluble alkali sulfates, C3A content and distribution of aluminate and silicate phases at the surface of cement grains, reactivity of cement phases, time, mixing energy and mixing method, water temperature, w/c, etc. The mechanisms by which chemical admixtures act are still a matter of controversy. It was documented that the combined effect of adsorption and nucleation are responsible for the hydration retardation induced by admixtures. Admixtures inhibit the contact of cement grains with water by adsorbing on to the surface of cement grains and the hydration products throughout the hydration process and thereby delay the hydration process. Retarders may also adsorb onto the nuclei of hydration products and can inhibit the further hydration. But at higher temperature, this layer can break down and the rate of hydration is accelerated. This may be one reason why prepared admixtures seem to increase the yield stress and viscosity at high temperature. Moreover, at lower dosage the adsorbed layer of admixture might not be sufficiently effective to act as a barrier to prevent the contact of water and cement grains, which promotes the acceleration of hydration reactions. This could be the reason why relatively higher yield stress and viscosity values were observed at low dosages of prepared admixtures. Moreover, lower water content reduces the space between solid particles. Hence, hydration products can easily come in closer contact with each other, resulting in faster rate of hydration reactions and earlier stiffening. This
Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011
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I. Aiad et al. / Egyptian Journal of Petroleum xxx (2018) xxx–xxx
Fig. 8. Plastic viscosity of oil well cement slurries (w/c = 0.40) at various temperatures and different dosages of admixture: a) CGS, b) AGS, c) MGS.
could probably be another reason why prepared admixtures acted as accelerators up to a certain dosage. 4. Conclusion 1. The rheological properties of OWC slurries are highly temperature dependent; they generally increased nonlinearly with increasing the temperature. This is mainly due to the dependence of the formation of hydration products on temperature. 2. As expected, the viscosity of OWC slurries decreased significantly with increase the w/c ratio. 3. The rheological properties of OWC slurries depend on the type of admixture used, AGS and MGS improved fluidity at all tested temperatures and for all dosages used. 4. The admixture dosage has a significant effect on the rheology of the slurry, at lower dosages CGS acted as accelerators.
Acknowledgment The authors are greatly thankful to Egyptian Petroleum Research Institute (EPRI) for financial and technical support. References [1] S. Ghabezloo, Effect of the variations of clinker composition on the poro elastic properties of hardened class G cement paste, Cem. Concr. Res. 41 (8) (2011) 920–922. [2] M. Economides, Well Cementing, Schlumberger Educational Services, Sugar Land, Texas, 1990. [3] , Fly Ash in Concrete: Production, Properties and Uses, Advances in Concrete Technology vol. 2 (1997) 269. [4] E.B. Nelson, M. Michaux, B. Drocho, Cement additives and mechanism of action, in: E.B. Nelson, D. Guillot (Eds.), Well Cementing, Schlumberger, Texas, 2006, pp. 49–91.
[5] D.K. Smith, Cementing, Monograph Series vol. 4 (1987) 264. [6] S. Popovics, in: Concrete Materials: Properties, Specifications, and Testing, second ed., Noyes Publication, 1992, p. 661. [7] API Specification 10A, in: Specifications for Cementing and Materials for Well Cementing, 23rd ed., 2002, p. 58. [8] H. Uchikawa, S. Hanehara, D. Sawaki, The role of steric repulsive force in dispersion of cement particles in fresh paste prepared with organic admixture, Cem. Concr. Res. 27 (1) (1997) 37–50. [9] K. Yamada, T. Takahashi, S. Hanehara, M. Matsuhisa, Effects of the chemical structure on the properties of the poly carboxylate-type superplasticizer, Cem. Concr. Res. 30 (2) (2000) 197–207. [10] F. Winnefeld, A. Zingg, R. Holzer, R. Figi, J. Pakusch, S. Becker, Interaction of polycarboxylate-based superplasticizers and cements: influence of polymer structure and C3A-content of cement, in: 12th ICCC, Montreal, 2007. [11] M.Y.A. Mollah, W.J. Adams, R. Schennach, D.L. Cocke, A review of cement superplasticizer interactions and their models, Adv. Cem. Res. 12 (4) (2000) 153–161. [12] C. Teodoriu, P. Asamba, Experimental study of salt content effect on class G cement properties with application to well integrity, J. Nat. Gas Sci. Eng. 24 (2015) 324–329. [13] I. Aiad, S. Abd El-Aleem, H. El-Didamony, Effect of delaying addition of some concrete admixtures on the rheological properties of cement pastes, Cem. Concr. Res. 32 (2002) 1839–1843. [14] L. Lei, J. Plank, Synthesis, working mechanism and effectiveness of a novel cycloaliphatic superplasticizer for concrete, Cem. Concr. Res. 42 (2012) 118– 123. [15] I. Aiad, M.S. Morsy, A.O. Habib, Influence of some low formaldehyde superplasticizers on the rheological and mechanical properties of cement pastes, J. Silicates Indus. 73 (2008) 71–76. [16] A.O. Habib, I. Aiad, T.A. Youssef, A.M. Abd El-Aziz, Effect of some chemical admixtures on the physico-chemical and rheological properties of oil well cement pastes, Constr. Build. Mater. 120 (2016) 80–88. [17] I. Aiad, A.M. Al-Sabbagh, S.H. Shafek, A.I. Adawy, S.A. Abo-El-Enein, Effect of some prepared superplasticizers (Cyclohexanone Based) on compressive strength and physico-chemical properties of oil well cement pastes, Egypt. J. Chem. 59 (5) (2016) 851–867. [18] A. Shahriar, M.L. Nehdi, Rheological properties of oil well cement slurries, Proc. ICE-Constr. Mater. 165 (2012) 25–44. [19] A. Shahriar, M. Nehdi, Modeling rheological properties of oil well cement slurries using multiple regression analysis and artificial neural networks, Int. J. Mater. Sci. 3 (2013) 26–37.
Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011
Contents lists available at ScienceDirect
Egyptian Journal of Petroleum journal homepage: www.sciencedirect.com
Full Length Article
Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries I. Aiad a, A.M. El-Sabbagh b, A.I. Adawy c,⇑, S.H. Shafek d, S.A. Abo-EL-Enein e a
Head of Petrochemicals Department, Egyptian Petroleum Research Institute, Egypt Director of Egyptian Petroleum Research Institute, Egypt c Surfactants Laboratory, Petrochemicals Department, Egyptian Petroleum Research Institute (EPRI), 1-Ahmed El-Zomor St., Nasr City, Cairo 11727, Egypt d Surfactants Laboratory, Petrochemicals Department, Egyptian Petroleum Research Institute, Egypt e Chemistry Department, Faculty of Science, Ain Shams University, Egypt b
a r t i c l e
i n f o
Article history: Received 4 January 2018 Revised 4 March 2018 Accepted 18 March 2018 Available online xxxx Keywords: Superplasticizers Rheological properties Apparent viscosity Plastic viscosity Yield stress
a b s t r a c t Three superplasticizers namely: cyclohexanone glyoxylic sulfanilate (CGS), acetone glyoxylic sulfanilate (AGS) and melamine glyoxylic sulfanilate (MGS) were prepared and characterized using FT-IR. The prepared admixtures were evaluated as additives for improving the rheological properties of oil well cement. The effect of temperature (25°, 45° and 65 °C) and admixture dose (0.25, 0.5, 0.75 and 1%) were determined on the apparent viscosity, plastic viscosity and yield stress. The results showed that the prepared superplasticizers, CGS, AGS and MGS decreased these parameters. The results concluded that the CGS, AGS and MGS admixtures act as retarders and dispersant for oil well cement. The three prepared admixtures exhibited high enhancement on the rheological properties which mean that it can use in oil cementing processes. Ó 2018 Egyptian Petroleum Research Institute. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction Oil well cement has been used in underground casing in oil and gas wells [1]. Cement slurry is placing in the annulus space between the geological formations surrounding to the well bore and well casing [2]. Oil well cementing was introduced in the twenties of the last century [3] with a number of objectives: to protect oil producing zones from water flow, to collapsing protect the well casing under pressure, to protect wells from corrosion and to protect ground water from oil and gas contamination [4,5]. OWC chemical composition is slightly different from that of regular Portland cement by lower C3A contents, are coarsely ground and have special retarders such as starch, sugars, etc, in addition to or in place of gypsum [6]. The American Petroleum Institute (API) Specifications for Materials and Testing for Well Cements [7] include requirements for eight classes of OWCs (classes A through H). A wide variety of chemical admixtures is currently available to enhance the OWCs physical properties such as fluidity and workability to achieve successful cementing process and required
Peer review under responsibility of Egyptian Petroleum Research Institute. ⇑ Corresponding author. E-mail address: [email protected] (A.I. Adawy).
compressive strength. They are adsorbed on the cement particles and act as dispersants by electrostatic and/or steric repulsion effects as demonstrated by Uchikawa et al. [8]. The admixture type and its chemical composition, dosages and the molecular structure of the admixtures [9,10] all of these parameters effect on workability of cement. In addition to the chemical composition of cement, especially the amount of C3A and the availability of sulfate attack during early hydration [11] also effect on the cementing process. So, the selection of the most suitable type and the optimum dosage of admixture in cement technology have increasing the importance [12,13]. The rheological properties of oil well cement (OWC) slurry determines the quality of the final product and helps predicting its end use performance and physical properties during and after processing. The rheology of OWC slurries is generally more complicated than that of conventional cement paste. The enhancement in the rheological properties of cement pastes depends on the cement composition and delaying addition time [14–16]. In order to deal with bottom whole conditions (wide range of pressure and temperature). This study aim to prepare three superplasticizers, CGS, AGS and MGS and studying their influence on the rheological properties of the oil well cement slurries. Also, the plastic viscosity and yield stress were determined.
https://doi.org/10.1016/j.ejpe.2018.03.011 1110-0621/Ó 2018 Egyptian Petroleum Research Institute. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011
2
I. Aiad et al. / Egyptian Journal of Petroleum xxx (2018) xxx–xxx
2. Materials
solution of polycondensation product, solid content of 40.9 wt%, was cooled to 25 °C.
2.1. Cement 2.3. Mixing and preparing cement slurry A freshly produced sample of class G moderate sulfate resistant oil well cement supplied by Schlumberger Company, Egypt was used. Its chemical composition was found to be: CaO, 60.4%; SiO2, 20.2%; Al2O3, 2.2%; Fe2O3, 2.7%; MgO; 6.0%; SO3, 3.0%; total alkali expressed as Na2O, 0.75%; insoluble residue, 0.75% and loss on ignition, 3%. The specific surface area as determined by the Blaine air-permeability method was found to be 3000 cm2/g. 2.2. Synthesis of superplasticizers 2.2.1. Sulfanilic acid-cyclohexanone glyoxylic condensate 270 g of water and 122.1 g (1.649 mol) of 50% aqueous glyoxylic acid are introduced into 1 L reaction vessel with a thermometer, stirrer, reflux condenser, pH equipment and dropping funnel. 123.4 g of 50% aqueous caustic soda was added while the contents of the vessel were stirred, and the pH was adjusted to 4.0. The temperature was raised to 50 °C and 133 g of cyclohexanone (1.00 mol) was added with continuous stirring. The contents of the vessel were stirred at 50 °C for further 75 min. until the original suspension was turned into a clear solution. The pH was raised during this time to 5.9. While cooling the solution, 88 g (0.509 mol) of sulfanilic acid and 48 g of 20% caustic soda were added simultaneously, this caused the pH dropped to 5.2. The reaction mixture was stirred at 90 °C until a final viscosity of 5.52 cSt (20 wt% solution at 20 °C) was obtained. The pH was adjusted to 10.0 by adding 39.2 g of 50 °C caustic soda to the reaction mixture. The clear aqueous solution of polycondensation product, with a solid content of 40.9 wt%, was cooled to 25 °C [17]. 2.2.2. Sulfanilic acid-acetone glyoxylic condensate 244.1 g (1.649 mol) of aq. glyoxylic acid (50%) and 270 g of water were added to a 1 L reaction flask with a three neck, reflux condenser, stirrer and dropping funnel. 123.4 g of 50% aq. NaOH was added with stirring and the pH was adapted to 4.0, the temperature was adjusted to 50 °C and 116 g of acetone (2.00 mol) was added with continuous stirring for 75 min. till the mixture was turned to a transparent solution. The pH was ascent during this period to 5.9. After cooling, 88 g (0.509 mol) of sulfanilic acid and 48 g of 20% aq. NaOH were added simultaneously, which caused the pH dropped to 5.2, the vessel content was stirred at 50 °C till obtained a viscosity of 5.52 cSt (20 wt% solution at 20 °C). Then the pH was adjusted to 10.0 by adding 39.2 g of 50% NaOH. 2.2.3. Sulfanilic acid-melamine glyoxylic condensate 270 g of water and 244.1 g (1.649 mol) of 50% aqueous glyoxylic acid were introduced into a 1 L reaction vessel with a thermometer, stirrer, reflux condenser, pH equipment and dropping funnel. 123.4 g of 50% aqueous caustic soda was added while the contents of the vessel were stirred, and the pH adjusted to 4.0. The temperature was raised to 50 °C and 126.1 g of melamine (1.00 mol) added with continues stirring. The contents of the vessel were stirred at 50 °C for a further 75 min until the original suspension was turned into a clear solution. The pH was raised during this time to 5.9. While cooling the solution, 88 g (0.509 mol) of sulfanilic acid and 48 g of 20% caustic soda were added simultaneously, this caused the pH dropped to 5.2. The reaction mixture was then stirred at 50 °C until a final viscosity of 5.52 cSt (20 wt% solution at 20 °C) was obtained. The pH was adjusted to 10.0 by adding 39.2 g of 50% caustic soda to the reaction mixture. Then the clear aqueous
The blender type mixer was used to prepared cement slurries according to the following procedure. The required water and the quantity of liquid admixture were poured into the blender. At a slow speed the mixing started for 15 s to disperse the chemical admixtures thorough the water. The cement was added to the admixed liquids over a period of 15 s. by a rubber spatula manual mixing was continued for 15 s to ensure homogeneity of material sticking to the mixing container wall. Finally, for another 35 s the mixing resumed at high speed. For all cement slurries the mixing procedure was strictly followed. All mixing was conducted at a controlled ambient room temperature of 23 ± 1 °C. The total time between the beginning of mixing and the start of the rheological tests was kept constant to avoid the effect of exogenous variables on the results. The rheometer set-up was also maintained constant for all slurries. The concentric cylinder test geometry was kept at the test temperature so as to avoid sudden thermal shock of the slurry. Cement slurries used in this study were prepared using moderate sulfate-resistant Class G oil well cement with a specific gravity of 3.15. The Distilled water was used for the mixing, and its temperature was maintained at 23 ± 1 °C using an isothermal container. A number of conventional chemical admixtures along with new-generation admixtures were used and their effects on the rheological properties of cement slurries at different temperatures were evaluated. These three synthetic admixtures sulfanilic acid-cyclohexanone glyoxylic (CGS), sulfanilic acid-acetone glyoxylic (AGS) and sulfanilic acid-melamine glyoxylic (MGS), (Scheme 1) were used by four different dosages 0.25%, 0.50%, 0.75% and 1% of weight of cement. 3. Results and discussion 3.1. Chemical structure The chemical structure of the prepared admixtures was confirmed by FTIR spectra. 3.1.1. FTIR spectra The FTIR spectra of the synthesized admixtures as shown in Fig. 1 showed the following absorption bands as shown in Table 1. IR spectra are represented in Fig. 1 referring to the hydrogen bonding intermolecular in the solid materials as the result of the coiling form of the polymer molecules. In all synthesized superplasticizers spectra, the characteristic absorption of the ether linkage (CAOAC) formed due to condensation of methylol groups, however, C@N stretching band in MGS appears at 1603 cm 1. The FTIR spectra confirmed the expected functional groups in the synthesized admixtures. 3.2. Effects of temperature and chemical admixtures on apparent viscosity The apparent viscosity results of OWC slurries at a shear rate of 31 s 1. A shear rate of 31 s 1 was chosen since it was the mean shear rate used in the experimental program. The apparent viscosity for cement slurries incorporating various dosages of CGS at different temperatures was presented in Fig. 2. It can be observed that the apparent viscosity decreased with increased CGS dosage at all investigated temperatures except 0.25% dosage showed increasing of apparent viscosity than blank. However, apparent viscosity values at 25 °C reached lower values
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I. Aiad et al. / Egyptian Journal of Petroleum xxx (2018) xxx–xxx
NH2
COONa
O
COONa
*
*
O
SO3Na
n
O
Cyclohexanone glyoxylic sulfanilate (CGS)
NH2
COOH
*
O
O
CHO
O
COONa
COONa
*
NH2 CH3 H3C
NaOH
SO3Na
n
SO3H
Acetone glyoxylic sulfanilate (AGS)
NH2 N H2N
N N
NH2
NH2 O
H N
COONa
COONa
*
*
N N
SO3Na
NH N
NH2
n
Melamine glyoxylic sulfanilate (MGS) Scheme 1. Synthetic route of CGS, AGS and MGS superplasticizers.
at higher CGS dosage. It appears that CGS acted as an accelerator at low dosage and as a retarder and dispersant at higher dosage. Apparent viscosity values of OWC slurries incorporating various AGS dosages is presented in Fig. 3. It can be observed that the apparent viscosity generally decreased with the increase of AGS dosage, and increased significantly with increasing the temperature. At 65 °C, no significant change in apparent viscosity was evident between dosages of 0.25 and 0.5%, but beyond this level the apparent viscosity decreased sharply. A sharp decrease in apparent viscosity was observed at dosage 0.75% and 1%. A similar trend was observed in the case of yield stress for OWC slurries. It appears that AGS acted as a retarder and dispersant at all dosages. Fig. 4 illustrates the apparent viscosity at different temperatures for cement slurries incorporating various dosages of MGS. It can be observed that the apparent viscosity decreased with increased MGS dosage at all investigated temperatures. It appears that MGS acted as a retarder and dispersant at all dosages.
3.3. Effects of temperature and chemical admixtures on yield stress Fig. 5 illustrates the yield stress values for OWC slurries incorporating various dosages of CGS at different temperatures. It can be observed that yield stress decreased significantly with increasing CGS dosage regardless of the temperature. The rate of decrease in yield stress was steeper at higher temperature. The differences between yield stress values measured at different temperatures (25 °C, 45 °C and 65 °C) decreased with higher dosage of CGS. Moreover, the higher the temperature, the higher was the admixture saturation dosage. The yield stress values of cement slurries incorporating various dosages of AGS and MGS are presented in Figs. 6 and 7. Yield stress values increased significantly with increasing temperature and decreased slightly with increasing admixture dosage. At 25 °C, the yield stress showed a sharp drop when the dosage increased from 0.50% to 1.00%. Beyond this dosage, there was no noticeable change in yield stress. At 65 °C a gradual decrease in yield stress
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I. Aiad et al. / Egyptian Journal of Petroleum xxx (2018) xxx–xxx
Fig. 1. FT-IR spectrum of: a) AGS, b) MGS.
Table 1 IR Characteristic bands of the synthesized superplasticizers. Compounds Band (cm
1
)
NH2 stretching CAOAC stretching C@O stretching C@N stretching C@C stretching S@O stretching CAH symmetric Stretching aliphatic
AGS
MGS
3376 1036–1185 1707 – 1514–1608 1392 –
3384 1033–1177 1571 1603 – – 2862
with increasing AGS and MGS dosage was observed. This is likely due to the fact that a higher AGS and MGS dosage offset the acceleration of hydration due to higher temperature. 3.4. Effects of temperature and chemical admixtures on plastic viscosity The plastic viscosity at different temperatures of OWC slurries incorporating different dosages of various admixtures was determined from the slope of the shear stress-shear strain down curve. The measured plastic viscosity does not always truly represent the material properly and sometimes could be misleading because of the high error involved in the fitting curve to the Bingham model. However, plastic viscosity was measured and presented in this
Fig. 2. Apparent viscosity of oil well cement slurries at various temperatures and different dosages of admixtures of CGS (w/c = 0.40).
section because it is very difficult to create mechanical models for the deformation behaviour of cement paste using the apparent viscosity at each shear rate point. As shown in Fig. 8, the plastic viscosity at 0.25% show a significant increasing with CGS dosage at all investigated temperatures. The sharply decrease showed at 0.5% then the plastic viscosity values gradually decrease with increasing CGS dosages. Also, the plastic viscosity at different temperatures for cement slurries incorporating various dosages of AGS and MGS is illustrated in Fig. 8.
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I. Aiad et al. / Egyptian Journal of Petroleum xxx (2018) xxx–xxx
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Fig. 3. Apparent viscosity of oil well cement slurries at various temperatures and different dosages of AGS admixture (w/c = 0.40).
Fig. 6. Yield stress of oil well cement slurries at various temperatures having different dosages of AGS admixture (w/c = 0.40).
Fig. 4. Apparent viscosity of oil well cement slurries at various temperatures and different dosages of MGS admixture (w/c = 0.40).
Fig. 7. Yield stress of oil well cement slurries at various temperatures having different dosages of MGS admixture (w/c = 0.40).
Fig. 5. Yield stress of oil well cement slurries at various temperatures and different dosages of CGS admixture (w/c = 0.40).
It is shown that plastic viscosity decreased with the increase of AGS or MGS dosages, and increased significantly with increasing the temperature at low AGS and MGS dosages. However, plastic viscosity values at all tested temperatures reached comparable values as the AGS and MGS dosages increased. As mentioned earlier, the rheology of OWC slurries depends on a number of factors, such as cement hydration kinetics, supporting liquid rheology, inter-particle forces, and solid volume fraction [18]. A number of chemical admixtures such as plasticizers/water reducer (dispersants), retarders, weighting agents, extenders, etc, have been used to modify the rheological properties of OWC slurries for proper placement in deep and narrow oil well annulus.
Most water reducing admixtures retard the cement hydration rate in addition to acting as a deflocculant due to electrostatic repulsion, steric repulsion, or both [19]. Moreover, the performance of chemical admixtures also depends on other factors including the type of cement and its fineness, nature and amount of calcium sulfates and soluble alkali sulfates, C3A content and distribution of aluminate and silicate phases at the surface of cement grains, reactivity of cement phases, time, mixing energy and mixing method, water temperature, w/c, etc. The mechanisms by which chemical admixtures act are still a matter of controversy. It was documented that the combined effect of adsorption and nucleation are responsible for the hydration retardation induced by admixtures. Admixtures inhibit the contact of cement grains with water by adsorbing on to the surface of cement grains and the hydration products throughout the hydration process and thereby delay the hydration process. Retarders may also adsorb onto the nuclei of hydration products and can inhibit the further hydration. But at higher temperature, this layer can break down and the rate of hydration is accelerated. This may be one reason why prepared admixtures seem to increase the yield stress and viscosity at high temperature. Moreover, at lower dosage the adsorbed layer of admixture might not be sufficiently effective to act as a barrier to prevent the contact of water and cement grains, which promotes the acceleration of hydration reactions. This could be the reason why relatively higher yield stress and viscosity values were observed at low dosages of prepared admixtures. Moreover, lower water content reduces the space between solid particles. Hence, hydration products can easily come in closer contact with each other, resulting in faster rate of hydration reactions and earlier stiffening. This
Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011
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Fig. 8. Plastic viscosity of oil well cement slurries (w/c = 0.40) at various temperatures and different dosages of admixture: a) CGS, b) AGS, c) MGS.
could probably be another reason why prepared admixtures acted as accelerators up to a certain dosage. 4. Conclusion 1. The rheological properties of OWC slurries are highly temperature dependent; they generally increased nonlinearly with increasing the temperature. This is mainly due to the dependence of the formation of hydration products on temperature. 2. As expected, the viscosity of OWC slurries decreased significantly with increase the w/c ratio. 3. The rheological properties of OWC slurries depend on the type of admixture used, AGS and MGS improved fluidity at all tested temperatures and for all dosages used. 4. The admixture dosage has a significant effect on the rheology of the slurry, at lower dosages CGS acted as accelerators.
Acknowledgment The authors are greatly thankful to Egyptian Petroleum Research Institute (EPRI) for financial and technical support. References [1] S. Ghabezloo, Effect of the variations of clinker composition on the poro elastic properties of hardened class G cement paste, Cem. Concr. Res. 41 (8) (2011) 920–922. [2] M. Economides, Well Cementing, Schlumberger Educational Services, Sugar Land, Texas, 1990. [3] , Fly Ash in Concrete: Production, Properties and Uses, Advances in Concrete Technology vol. 2 (1997) 269. [4] E.B. Nelson, M. Michaux, B. Drocho, Cement additives and mechanism of action, in: E.B. Nelson, D. Guillot (Eds.), Well Cementing, Schlumberger, Texas, 2006, pp. 49–91.
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Please cite this article in press as: I. Aiad et al., Effect of some prepared superplasticizers on the rheological properties of oil well cement slurries, Egypt. J. Petrol. (2018), https://doi.org/10.1016/j.ejpe.2018.03.011