Research And Application On Rheological Property Of Cement Slurry

Well cementing engineering as the important link in oil and gas well,was the key of the enhanced oil recovery and reasonable exploitation of petroleum resources.Cement slurry was the main material of using packing formation and bracing casing. Cement slurry composed of difference mineral, release heat within reaction process with water. It affected the cement slurry property and the cementation quality. So it was the fundamental guarantee of the cementing quality to master and follow the real hydration. The foundation of optimizing the designing the slurry and forecasting the rheology of cement slurry improving the efficiency of replacement was provided.Kinetic analysis of oil well cement indicated the reaction of the each stages of cement hydration machine consists of three parts ground and obtained the variation equation of each stage. Thermodynamic analysis of cement hydration indicated that the research of hydration can be simplified to the real-time monitoring of hydration temperature-rise and research the law of the variation. It reflects the real hydration heat of the slurry. Hydration law was studied under different temperatures, water to cement ratios and admixtures by means of measurement of the heat of hydration by self-developed automatic temperature measurement system of slurry. Hydration model was established by the comprehensive analysis of experimental data. The model mainly reflected the impact on hydration heat of the temperature and water-cement ratio. The model can reflect the real process of heat release rate of hydration and Improved accuracy of data processing and forecasting.The results demonstrate that high temperature can obviously increase the temperature-rise of the cement and accelerate the hydration process. The temperature-rise of the cement changed clearly under low temperature and differences are smaller of the slurry under low temperature. Higher water to cement ratios can reduce the temperature-rise. The process of cement hydration was changed with adding different additives. Dispersant and fluid loss reducer can accelerate the early hydration and delay post-hydration. Dosage of retarder caused significant change in hydration temperature. With the increase in the dosage of retarder, Induction period was extended and the peak temperature-rise was reduced. CaCl₂ can increase temperature-rise. The impact on temperature-rise is lager with CaCl₂. But more CaCl₂ will cause excessive temperature-rise. Both slag and fly ash can reduce the temperature-rise and retard the time to peak. In the extent of reducing temperature-rise,slag is not obviously as good as fly ash. And more slag can increase the later temperature-rise.Based on the experimental results, the rheological model of cement slurry was established. For the relationgship between temperature, water-cement ratio, temperature - water-cement ratio, temperature-hydration time and the rheological parameters, the model of rheological parameterswas established. Analysis of the model show that the model was more accurate grasp of the rheological properties of slurry by taking into account the actual factors of temperature and water-cement ratio. The foundation of grasping the rheology of slurry and designing the slurry was provided.It was shown that the rheology of slurry was better with the increase of w/c. Influence law of temperature on rheology was different within specific temperature range. With the curing time extended, the rheological model was not changed. Dispersant, fluid loss and retarder can improved to varying degrees slurry rheology. The relationship between the rheological and the dosage of accelerator was affect by temperature obviously. The properties of fluid loss reducer were rapid declined under high temperature. Retarding effect of the citric acid was independent of temperature. The rheology of slurry was improved when adding the admixture at higher temperature. Rheology of slurry is better. The results also show that the influence of the particle size of cement slurry on rheology clearly.Using the rheological model established, the study on numerical simulation of replacement of cement would reflect the actual cementing accurately ,and improve the simulation accuracy. It was shown that the conclusions consist of displacement efficiency in stopper and turbulent flow is higher than that in laminar flow, the law which the fluid influence displacement efficiency in different patterns is similar. The simulated results indicate that it was helpful to increase the displacement efficiency when the flow behavior index and consistency coefficient was choosed rational, and increasing the yield stress can not affect the displacement efficiency. And the well deviation and eccentricity would reduce the efficiency of replacement.Theoretical foundation of cementing design optimization and improving cementing quality was provided. And the result would benefit to guide the construction site.