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The chemical shrinkage and corrugated tube test methods were used to study the shrinkage behaviour of Class G oil well cement with water-to-cement (w/c) ratios of 0.3 and 0.5, cured at temperatures from 15 to 60°C. The experimental results show that the typical linear shrinkage evolution curve of a cement slurry obtained by corrugated tube method h...
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1 cement paste cured at high temperature 2 Mingliang Zhang, Master student, ABSTRACT 15 With the extensive increase exploitation of shale gas/oil, the mechanical/physical properties of 16 oil well cement paste (OWCP) are highly paid special attention to. The mechanical and physical 17 properties of OWCP is believed to be closely related to its micr...
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... The inflection point of the sonic property evolution curve (which represents the point at which sonic property starts to change) as measured by UCA can be considered as an approximation of the setting time (final set time) of cements. The final set time measured by Vicat apparatus has been previously observed to correlates well with the inflection point on autogenous shrinkage curves obtained by corrugated tube test method [62]. The setting time under various temperatures decreased sequentially from 110 • C, 150 • C, 180 • C, 130 • C to 200 • C, which was consistent with HOH and CS test results. ...
... This phenomenon agrees well with Fig. 7 and other previous studies [64]. As CH is generally considered to be detrimental to the bond in cementitious materials [88], the higher CH content at higher w/c ratio will contribute to the lower mechanical strength of the set cement. Additionally, the hydration progress as a function of time showed that the plateau stage was reached at later time under higher w/c ratio, which was also reflected by the decrease of all rate constants with increasing w/c ratio (Table 4). ...
A broad experimental program has been performed to characterize the hydration and strength development of a Class G oil well cement under various curing temperatures from 15 to 87 °C. The progress of hydration was monitored by isothermal calorimetry, thermo-gravimetric analysis, and quantitative X-ray diffraction based on Rietveld refinement; while the strength development was evaluated by both nondestructive ultrasonic tests and destructive crush tests. Test results indicate that heat of hydration, non-evaporable water content and degree of hydration of the cement follow approximately linear relationships, which are largely independent of curing temperature; the obtained proportionality constants agree well with those estimated by previously proposed empirical equations. The influences of curing temperature on the hydration rate and strength development rate can be modeled by an equivalent age method coupled with the Arrhenius law. The apparent activation energy obtained from hydration analysis was higher than that obtained from strength development analysis.
Understanding cement shrinkage behavior in offshore well cement sheaths is crucial for assessing integrity and preventing potential issues. This study investigates the correlation between early strength development and shrinkage to assist in cement paste design. In this research, one cement paste was formulated with water-to-cement ratio of 0.36 and cured under different conditions, including temperatures of 40 °C, 60 °C and 80 °C, and a pressure of 1.0 kpsi. The development of the cement pastes was analyzed using ultrasonic pulse velocity and volumetric shrinkage tests over a period of 90 hours. By employing specific markers of percolation in each test, the results were synchronized, enabling the correlation of data to better understand the evolution of shrinkage and its relationship to transit time.
The results obtained from the experimental testing showed a clear correlation between the normalized evolutions of transit time and cement shrinkage for the 3 testing conditions. The findings of this study allow the practitioner to understand when and how shrinkage will occur, with respect to a routine test, the ultrasonic pulse velocity. The results can feed numerical models of early cement behavior. This will support better decisions about well operations to be performed during the wait-on-cement time and in the following days, improving its performance as a well barrier.
A comprehensive experimental investigation of Portland cement hydration kinetics in a wide temperature range from 35 °C to 150 °C with pressure up to 50 MPa was performed by heat of hydration, chemical shrinkage and ultrasonic measurements. Increasing curing temperature was found to have a stronger acceleration effect during the main hydration period while increasing curing pressure had a stronger acceleration effect during the pre-induction period of cement hydration. By comparing chemical shrinkage test results with other methods of estimating cement degree of hydration, such as quantitative X-ray diffraction, non-evaporable water content measured by thermogravimetric analysis, as well as heat of hydration, it was observed that total chemical shrinkage of cement at complete hydration decreased with curing temperature from 35 °C to 75 °C and then stayed stable between 75 °C and 150 °C. Similarly, the P-wave velocity of cement (which is an indicator of physical and mechanical properties) as a function of hydration degree decreased with increasing curing temperature in the range between 35 °C to 75 °C, then remained relatively stable between 75 °C and 130 °C. The reduction of gel water content in C–S–H from 35 °C to 75 °C is believed to be the primary cause of these observed phenomena.
